Abstract:
A process for converting molybdenum technical oxide into a purified molybdenum trioxide product is provided, generally comprising the steps of: combining molybdenum technical oxide with an oxidizing agent and a leaching agent in a reactor under suitable conditions to effectuate the oxidation of residual MoS 2 , MoO 2  and other oxidizable molybdenum oxide species to MoO 3 , as well as the leaching of any metal oxide impurities; precipitating the MoO 3  species in a suitable crystal form; filtering and drying the crystallized MoO 3  product; and recovering and recycling any solubilized molybdenum.

Description:
[0001]    Molybdenum is principally found in the earth&#39;s crust in the form of molybdenite (MOS 2 ) distributed as very fine veinlets in quartz which is present in an ore body comprised predominantly of altered and highly silicified granite. The concentration of the molybdenite in such ore bodies is relatively low, typically about 0.05 wt % to about 0.1 wt %. The molybdenite is present in the form of relatively soft, hexagonal, black flaky crystals which are extracted from the ore body and concentrated by any one of a variety of known processes so as to increase the molybdenum disulfide content to a level of usually greater than about 80 wt % of the concentrate. The resultant concentrate is subjected to an oxidation step, which usually is performed by a roasting operation in the presence of air, whereby the molybdenum disulfide is converted to molybdenum oxide, which is of a commercial or technical grade (technical oxide) containing various impurities including metallic contaminants present in the original ore body. 
         [0002]    It is desirable or necessary in some instances to provide a molybdenum trioxide (MoO 3 ) product that is relatively free of metallic contaminants, as well as possessing a low concentration of molybdenum dioxide (MoO 2 ), or other molybdenum oxide species with a valency lower than +6, such as, for example, MO 4 O 11 , which, for the sake of simplicity herein, will also be referred to as MoO 2 . This high purity material may be used for the preparation of various molybdenum compounds, catalysts, chemical reagents or the like. As used herein, the term molybdenum technical oxide means any material comprising anywhere from about 1 wt % to about 99 wt % MoO 2 , and may optionally further comprise MoS 2  or other sulfidic molybdenum, iron, copper, or lead species. The production of high purity MoO 3  has previously been achieved by various chemical and physical refining techniques, such as the sublimation of the technical oxide at an elevated temperature, calcination of crystallized ammonium dimolybdate, or various leaching or wet chemical oxidation techniques. However, these processes may be expensive and often result in low yields and/or ineffective removal of contaminants. 
         [0003]    One embodiment of the present invention provides a process for converting molybdenum technical oxide into a purified molybdenum trioxide product. Generally, the process comprises the steps of: combining molybdenum technical oxide with an oxidizing agent and a leaching agent in a reactor under suitable conditions to effectuate the oxidation of residual MoS 2 , MoO 2  and other oxidizable molybdenum oxide species to MoO 3 , as well as the leaching of any metal oxide impurities; precipitating the MoO 3  species in a suitable crystal form; filtering and drying the crystallized MoO 3  product; and recovering and recycling any solubilized molybdenum. Depending on process conditions, the solid product may be precipitated as crystalline or semi-crystalline H 2 MoO 4 , H 2 MoO 4 ·H 2 O, MoO 3  or other polymorphs or pseudo-polymorphs. The reaction may be performed as a batch, semi-continuous, or continuous process. Reaction conditions may be chosen to minimize the solubility of MoO 3  and to maximize the crystallization yield. Optionally, seeding with the desired crystal form may be utilized. The filtrate may be recycled to the reactor to minimize MoO 3  losses, as well as oxidizing agent and leaching agent consumption. A portion of the filtrate may be purged to a recovery process wherein various techniques may be employed, such as precipitation of molybdic acid with lime or calcium carbonate to form CaMoO 4 , precipitation as Fe 2 (MoO 4 ) 3 ·xH2O and other precipitations, depending on chemical composition. Likewise, ion exchange or extraction may be employed, for example, anion exchange employing caustic soda regeneration to obtain a sodium molybdate solution that is recycled to the reaction step and crystallized to MoO 3 . Metal oxide impurities may also be separately treated, e.g., by ion exchange, for recovery and/or to be neutralized, filtered and discarded. 
     
    
     
       DESCRIPTION OF THE FIGURES 
         [0004]    The following figures form part of the present specification and are included to further demonstrate certain aspects of the present invention. The invention may be better understood by reference to one or more of these figures in combination with the detailed description of specific embodiments presented herein. 
           [0005]      FIG. 1  shows a block flow diagram of the process of the present invention. 
           [0006]      FIG. 2  shows the dissolution of MoO 3  in HNO 3 . 
           [0007]      FIG. 3  shows the variability of leaching metal impurities with HNO 3 . 
           [0008]      FIG. 4  shows the oxidation of MoO 2  in H 2 SO 4  (fixed)/HNO 3  (variable) solutions. 
           [0009]      FIG. 5  shows the dissolution of MoO 3  in H 2 SO 4  (fixed)/HNO 3  (variable) solutions. 
           [0010]      FIG. 6  shows the dissolution of MoO 3  in H 2 SO 4  (variable)/HNO 3  (fixed) solutions. 
           [0011]      FIG. 7  shows the variability of leaching metal impurities with H 2 SO 4  (variable)/HNO 3  (fixed) solutions. 
           [0012]      FIG. 8  shows the oxidation of MoO 2  in H 2 SO 4  (variable)/HNO 3  (fixed) solutions 
           [0013]      FIG. 9  shows the oxidation of MoO 2  in H 2 SO 4 /H 2 O 2  solutions. 
           [0014]      FIG. 10  shows the oxidation of MoO 2  in H 2 SO 4 /KMnO 4  or KS 2 O 8  solutions. 
           [0015]      FIG. 11  shows the oxidation of MoO 2  in Caro&#39;s acid solutions. 
       
    
    
     DESCRIPTION OF THE INVENTION 
     Technical Oxide: 
       [0016]    Technical oxides suitable for use in the present invention are available from several commercial sources. Table 1 below provides a few non-limiting examples of technical oxides suitable for use with the processes described herein. It should be noted that besides technical oxides similar to those presented, molybdenum disulfide could also be employed as a raw material. The following elemental analysis was conducted using sequential X-ray Fluorescence Spectrometry (XRF) and Inductively Coupled Plasma (ICP) Spectrometry. For the ICP analyses, samples were dissolved in aqueous ammonia wherein the MoO 3  dissolved and insolubles were filtered. The molybdenum from the ammonium dimolybdate solution is labeled as MoO 3  in the table and the molybdenum from the insolubles is denoted MoO 2 . 
         [0000]    
       
         
               
               
               
               
             
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                   
                 TABLE 1 
               
             
             
               
                   
                   
               
               
                   
                 Sample 1 
                 Sample 2 
                 Sample 3 
               
             
          
           
               
                   
                 XRF 
                 ICP 
                 XRF 
                 ICP 
                 XRF 
                 ICP 
               
               
                   
                   
               
             
          
           
               
                 MoO 2   
                   
                 31.7 
                   
                 3.6 
                   
                 9.5 
               
               
                 MoO 3   
                 87.4 
                 60.5 
                 87.3 
                 90.2 
                 92.2 
                 79.6 
               
               
                 CuO (mg/kg) 
                 2000 
                 1600 
                 600 
                 500 
                 3000 
                 3200 
               
               
                 PbO (mg/kg) 
                   
                   
                 500 
               
               
                 CaO (mg/kg) 
                 6000 
                 8300 
                 600 
                 300 
                 2000 
                 2300 
               
               
                 Na (mg/kg) 
                   
                   
                 500 
               
               
                 S (mg/kg) 
                   
                   
                 500 
               
               
                 TiO 2  % 
                 0.1 
               
               
                 Al 2 O 3  % 
                 0.7 
                   
                 0.51 
                 0.67 
                   
                 0.35 
               
               
                 K 2 O % 
                 0.4 
                 0.33 
                   
                 0.18 
                 0.2 
                 0.13 
               
               
                 SiO 2 % 
                 6.1 
                   
                 4.9 
                 4 
                 5 
                 7.4 
               
               
                 Fe % 
                 2.31 
                 2.45 
                 0.14 
                 0.12 
                 0.56 
                 0.59 
               
               
                 Na 2 O % 
                   
                 0.06 
               
               
                 MgO % 
                 0.2 
                 0.27 
               
               
                   
               
             
          
         
       
     
         [0017]    Referring now to  FIG. 1 , the technical oxide and/or molybdenum sulfide raw materials are introduced into a reaction vessel (100), preferably a jacketed, continuously-stirred tank reactor, but any suitable reaction vessel may be employed. The raw material is mixed in the reaction vessel (100) with a leaching agent, to dissolve metal impurities, and an oxidizing agent, to oxidize MoS 2  and MoO 2  to MoO 3 . 
         [0018]    While any common lixiviant, or mixtures of common lixiviants, may be employed, sulfuric acid and hydrochloric acid are preferred leaching agents. Similarly, while any common oxidizing agent, or mixtures of common oxidizing agents, may be employed, including but not limited to hypochlorite, ozone, oxygen-alkali, acid permanganate, persulfate, acid-ferric chloride, nitric acid, chlorine, bromine, acid-chlorate, manganese dioxide-sulfuric acid, hydrogen peroxide, Caro&#39;s acid, or bacterial oxidation, Caro&#39;s acid and chlorine are the preferred oxidizing agents. 
         [0019]    The leaching agent and oxidizing agent may be added in any order, or may be added together such that the leaching and oxidation occur simultaneously. In some instances, such as when using Caro&#39;s acid, leaching and oxidation occur by the action of the same reagent. In other instances, the leaching agent may be formed in situ by the addition of an oxidizing agent, for example, the addition of chlorine or bromine to the reaction mass results in the formation of hydrochloric or hydrobromic acid. The reaction mass is agitated in the reaction vessel (100) for a suitable time and under suitable process conditions to effectuate the oxidation of residual MoS 2 , MoO 2  and other oxidizable molybdenum oxide species to MoO 3 , and to leach any metal oxide impurities, say for example between about 15 minutes to about 24 hours at a temperature ranging from about 30° C. to about 150° C. Depending on the particular oxidizing agent employed, the reaction pressure may range from about 1 bar to about 6 bar. Depending on the lixiviant employed, the pH of the reaction mass may range from about −1 to about 3. Whereas the lixiviant and oxidizer may act separately when dosed one after another, it has been observed that simultaneous action of lixiviant and oxidizer is beneficial for driving both the oxidation and leaching reactions to completeness. 
         [0020]    While leaching of impurities and oxidization of MoS 2  and MoO 2  occurs, the majority of the MoO 3  precipitates, or crystallizes, from the solution. However, a portion of the MoO 3  formed by oxidation or dissolved from MoO 3  in the starting material may remain in solution for various reasons. While not intending to be bound by theory, it is generally believed that wet-chemical oxidation in a slurry process is mechanistically explained by either oxidative dissolution of species at the solid-liquid interface, or by dissolution, perhaps slow dissolution, of the oxidizable species followed by oxidation in the liquid phase. The most probable form of Mo 6+  species in solution, denoted as dissolved MoO 3 , is believed to be H 2 MoO 4 , but a variety of other species are also possible. It has been observed that when the oxidation is not complete, blue colored solutions with a high amount of dissolved molybdenum oxide species result, the blue color pointing at polynuclear mixed Mo 5+ /Mo 6+  oxidic species. Also, crystallization is a slow process at low temperatures, so the crystallization conditions chosen may result in a lower or higher amount of dissolved molybdenum oxide species. Thus, after the precipitated trioxide, together with hitherto undissolved MoO3 or other species from the starting technical oxide is removed by filtration (200), the filtrate can be recycled to the reaction vessel (100). Because the leached metal impurities will also be recycled to the reaction vessel (100), a slipstream of the recycled material may be drawn off and treated for removal or recovery of the metal impurities. The filter cake (MoO 3  product) may be dried (400) and packed for distribution (500). 
         [0021]    In order to recover any molybdenum in the slipstream, it may be treated in a suitable ion-exchange bed (300). One preferred ion-exchange bed comprises a weakly basic anion exchange resin (cross-linked polystyrene backbone with N,N′-di-methyl-benzylamine functional groups), preloaded with sulfate or chloride anions, wherein molybdate ions are exchanged with sulfate or ions chloride ions during resin loading and the resin is unloaded with dilute sodium hydroxide, about 1.0 to 2.5 M. The unloaded molybdenum is recovered by recycling the dilute sodium molybdate (Na 2 MoO 4 ) stream (regenerant) to the reaction vessel (100). 
         [0022]    Following recovery of molybdenum, the slipstream may be subsequently treated in additional ion-exchange beds (600) in order to remove additional metallic species. Any remaining metal impurities will be precipitated (700) and filtered (800) for final disposal. After these treatment steps a residual solution is obtained containing mainly dissolved salts like NaCl or Na 2 SO 4 , depending on the chemicals selected that may be purged. 
       EXAMPLES 
       [0023]    It should be noted that within the following discussion several stoichiometric schemes are discussed. While not desiring to be bound by any theory, the inventors herein believe that the disclosed schemes accurately describe the discussed mechanisms. 
         [0024]    75 grams of technical oxide was mixed with 250 ml of various acidic solutions listed and described below. The mixtures were stirred with a Teflon coated magnetic stirrer and heated to 70° C. for two hours. The mixtures were cooled to room temperature and filtered over a 90 mm black ribbon filter. The filter cake was washed with 20 ml of deionized water. The filtrate was brought to 250 ml volume and the filter cake was dried overnight at 120° C. The dried filter cake was analyzed for content, as well as metal impurities. The filtrate was analyzed for metal impurities. 
       Nitric Acid: 
       [0025]    The leaching of the technical oxide (TO) and calcined technical oxide (TOC) was performed in a series of acid solutions from 0.1 to 10 N HNO 3 . Leaching and oxidation occurs by action of the single reagent. The oxidation stoichiometry can be summarized as follows: 
         [0000]      MoO 2 +2H + +2(NO 3 ) − →MoO 3 +2NO 2 (g)⇑+H 2 O 
         [0000]    MoO 2  in the sample was completely converted to MoO 3  with nitric acid. A color change was also visible form dark blue (Mo 5+ ) to grass green/blue green. The solubility of MoO 3  decreases with acid concentration as shown in  FIG. 2 . Cu and Fe dissolve readily in low concentrations of nitric acid. Some metals (Ba, Pb, Sr, and Ca) needed more the 1 N nitric acid to dissolve as shown in  FIG. 3  and Table 2. Brown NO 2  fumes were visible with excess HNO 3 . The results of the leaching/oxidation of technical oxide with nitric acid are summarized in Table 2. 
         [0000]    
       
         
               
               
               
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                   
                   
                   
                   
                 EX E. 
                 EX. F 
                 EX. G 
                 EX. H 
                 EX. I 
                 EX. J 
                 EX. K 
                 EX. L 
               
               
                   
                   
                   
                   
                   
                 Cal- 
                 Cal- 
                 Cal- 
                 Cal- 
                 Cal- 
                 Cal- 
                 Cal- 
                 Cal- 
               
               
                   
                 EX. A 
                 EX. B 
                 EX. C 
                 EX. D 
                 cined 
                 cined 
                 cined 
                 cined 
                 cined 
                 cined 
                 cined 
                 cined 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 Intake 
                 intake g 
                 75 
                 75 
                 75 
                 75 
                 75 
                 75 
                 75 
                 75 
                 75 
                 75 
                 75 
                 75 
               
               
                   
                 liquid ml 
                 250 
                 250 
                 250 
                 250 
                 250 
                 250 
                 250 
                 250 
                 250 
                 250 
                 250 
                 250 
               
               
                   
                 N HNO3 
                 4 
                 6 
                 8 
                 10 
                 0 
                 0.1 
                 1 
                 2 
                 4 
                 6 
                 8 
                 10 
               
               
                   
                 solids % 
                 22.50 
                 22.50 
                 22.50 
                 22.50 
                 22.50 
                 22.50 
                 22.50 
                 22.50 
                 22.50 
                 22.50 
                 22.50 
                 22.50 
               
               
                   
                 leaching 
                 70 
                 70 
                 70 
                 70 
                 70.00 
                 70.00 
                 70.00 
                 70.00 
                 70.00 
                 70.00 
                 70.00 
                 70.00 
               
               
                   
                 temp ° C. 
               
               
                   
                 leaching 
                 2 
                 2 
                 2 
                 2 
                 2.00 
                 2.00 
                 2.00 
                 2.00 
                 2.00 
                 2.00 
                 2.00 
                 2.00 
               
               
                   
                 time hrs 
               
               
                 filtercake 
                 % SiO2 
                 4.00 
                 4.20 
                 3.50 
                 4.00 
                 6.80 
                 4.30 
                 3.90 
                 4.50 
                 5.30 
                 4.00 
                 4.30 
                 4.40 
               
               
                 500° C. 
                 % K2O 
                 &lt;0.1 
                 &lt;0.1 
                 &lt;0.1 
                 &lt;0.1 
                 &lt;0.1 
                 0.10 
                   
                   
                   
                   
                 &lt;0.1 
                 &lt;0.1 
               
               
                 XRF 
                 % CaO 
                 &lt;0.1 
                 &lt;0.1 
                 &lt;0.1 
                 &lt;0.1 
                 0.20 
                 0.20 
                 &lt;0.1 
                 &lt;0.1 
                 &lt;0.1 
                   
                 &lt;0.1 
                 &lt;0.1 
               
               
                 method 
                 % Fe2O3 
                 &lt;0.1 
                 &lt;0.1 
                 &lt;0.1 
                 &lt;0.1 
                 0.70 
                 0.10 
                 &lt;0.1 
                 &lt;0.1 
                 &lt;0.1 
                 &lt;0.1 
                 &lt;0.1 
                 &lt;0.1 
               
               
                 Uniquant 
                 % MoO3 
                 94.30 
                 94.40 
                 94.40 
                 94.40 
                 91.90 
                 93.50 
                 94.20 
                 94.50 
                 92.90 
                 94.30 
                 94.10 
               
               
                   
                 % CdO 
                 &lt;0.1 
                 &lt;0.1 
                 &lt;0.1 
                 &lt;0.1 
                   
                   
                   
                   
                   
                   
                 &lt;0.1 
                 &lt;0.1 
               
               
                   
                 % ThO2 
                 &lt;0.1 
                 &lt;0.1 
                 &lt;0.1 
                 &lt;0.1 
                   
                   
                   
                   
                   
                   
                 &lt;0.1 
                 &lt;0.1 
               
               
                 filtercake 
                 % MoO2 
                 0.23 
                 0.19 
                 0.13 
                 0.16 
                   
                   
                   
                   
                   
                   
                   
                 &lt;0.5 
               
               
                 120° C. 
                 % MoO3 
                 89.56 
                 89.70 
                 90.90 
                 91.89 
                   
                   
                   
                   
                   
                   
                   
                 91.00 
               
               
                 filtrate 
                 Al 
                 330 
                 315 
                 341 
                 314 
                 240 
                 450 
                 490 
                 475 
                 450 
                 470 
                 420 
                 365 
               
               
                 ICP 
                 Ca 
                 400 
                 360 
                 430 
                 380 
                 65 
                 95 
                 505 
                 490 
                 460 
                 510 
                 480 
                 415 
               
               
                 analyses 
                 Mg 
                 35 
                 32 
                 37 
                 34 
                 25 
                 40 
                 45 
                 40 
                 40 
                 45 
                 40 
                 35 
               
               
                 mg/l 
                 Na 
                 29 
                 25 
                 33 
                 22 
                 40 
                 35 
                 50 
                 45 
                 45 
                 50 
                 45 
                 40 
               
               
                   
                 P 
                 26 
                 19 
                 27 
                 13 
                 30 
                 35 
                 35 
                 35 
                 35 
                 40 
                 40 
                 30 
               
               
                   
                 S 
                 62 
                 75 
                 80 
                 65 
                 45 
                 50 
                 65 
                 60 
                 60 
                 70 
                 65 
                 55 
               
               
                   
                 Sr 
                 22 
                 23 
                 23 
                 19 
                 5 
                 10 
                 25 
                 25 
                 25 
                 25 
                 25 
                 20 
               
               
                   
                 Cu 
                 673 
                 630 
                 710 
                 630 
                 630 
                 840 
                 885 
                 860 
                 810 
                 900 
                 820 
                 685 
               
               
                   
                 Fe 
                 1477 
                 1406 
                 1611 
                 1425 
                 560 
                 1650 
                 1860 
                 1900 
                 1800 
                 2030 
                 1860 
                 1550 
               
               
                   
                 Mo 
                 2942 
                 4770 
                 1480 
                 2610 
                 9260 
                 8300 
                 6190 
                 8260 
                 6330 
                 2780 
                 1325 
                 1400 
               
               
                   
                 Pb 
                 29 
                 46 
                 58 
                 49 
                 &lt;5 
                 &lt;5 
                 &lt;5 
                 29 
                 33 
                 68 
                 62 
                 54 
               
               
                   
                 Ti 
                 7 
                 13 
                 9 
                 5 
                 20 
                 10 
                 25 
                 25 
                 20 
                 40 
                 15 
                 15 
               
               
                   
                 Zn 
                 17 
                 17 
                 18 
                 15 
                 15 
                 20 
                 20 
                 20 
                 20 
                 20 
                 20 
                 15 
               
               
                   
                 K 
                 400 
                 375 
                 330 
                 235 
                 160 
                 70 
                 190 
                 190 
                 180 
                 230 
                 210 
                 180 
               
               
                   
                 Ag 
                   
                   
                   
                   
                 &lt;5 
                 &lt;5 
                 &lt;5 
                 8 
                 7 
                 7 
                 6 
                 7 
               
               
                   
                 Ba 
                   
                   
                   
                   
                 3 
                 2 
                 11 
                 14 
                 10 
                 14 
                 12 
                 10 
               
               
                   
               
             
          
         
       
     
       Sulfuric Acid/Nitric Acid: 
       [0026]    Keeping the concentration of H 2 SO 4  fixed at 4N and varying the concentration of HNO 3  from 0 to 2 N in six increments, a series of acidic solutions were prepared. Technical oxide was mixed in each of the solutions and the results of the leaching/oxidation with H 2 SO 4 /HNO 3  mixtures are summarized in Table 3. Brown NO 2  fumes were visible with excess HNO 3 . The color of the solution changed from dark blue to light grass green. The oxidation was almost complete starting from 0.2 N HNO 3 . See  FIG. 4 . The dissolution of MoO 3  in varying concentrations of the acidic solution is shown in  FIG. 5 . Ca, Fe and Cu dissolve well, but Pb did not dissolve. 
         [0000]    
       
         
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
             
           
               
                   
                 TABLE 3 
               
               
                   
                   
               
               
                   
                 EX. 2A 
                 EX. 2B 
                 EX. 2C 
                 EX. 2D 
                 EX. 2E 
                 EX. 2F 
                 EX. 2G 
                 EX. 2H 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 Intake 
                 intake g 
                 75 
                 75 
                 75 
                 75 
                 75 
                 75 
                 75 
                 75 
               
               
                   
                 liquid ml 
                 250 
                 250 
                 250 
                 250 
                 250 
                 250 
                 250 
                 250 
               
               
                   
                 N H2SO4 
                 4N 
                 4N 
                 4N 
                 4N 
                 4N 
                 4N 
                 4N 
                 4N 
               
               
                   
                 ml H2SO4 96% 
                 28 
                 28 
                 28 
                 28 
                 28 
                 28 
                 28 
                 28 
               
               
                   
                 N HNO3 
                 0.00 
                 0.10 
                 0.25 
                 0.50 
                 1.00 
                 1.50 
                 2.00 
                 0.00 
               
               
                   
                 ml HNO3 65% 
                 0.00 
                 1.74 
                 5.22 
                 8.70 
                 17.66 
                 26.16 
                 34.67 
                 0.00 
               
               
                   
                 solids % 
                 22.50 
                 22.50 
                 22.50 
                 22.50 
                 22.50 
                 22.50 
                 22.50 
                 22.50 
               
               
                   
                 leaching 
                 70 
                 70 
                 70 
                 70 
                 70 
                 70 
                 70 
                 70 
               
               
                   
                 temp ° C. 
               
               
                   
                 leaching 
                 2 
                 2 
                 2 
                 2 
                 2 
                 2 
                 2 
                 2 
               
               
                   
                 time hrs 
               
               
                 filtercake 
                 % MgO 
               
               
                 500° C. XRF 
                 % SiO2 
                 7.40 
                 7.40 
                 7.30 
                 7.90 
                 7.10 
                 6.90 
                 7.00 
                 7.40 
               
               
                 method 
                 % K2O 
                 0.10 
                 0.10 
                 0.10 
                 0.10 
                 &lt;0.1 
                 0.10 
                 0.10 
                 0.10 
               
               
                 Uniquant 
                 % CaO 
               
               
                   
                 % Fe2O3 
                 0.10 
                 0.10 
                 &lt;0.1 
                 &lt;0.1 
                 &lt;0.1 
                 &lt;0.1 
                 &lt;0.1 
                 &lt;0.1 
               
               
                   
                 % MoO3 
                 91.90 
                 92.10 
                 92.20 
                 91.60 
                 92.70 
                 92.70 
                 92.60 
                 92.20 
               
               
                   
                 % CdO 
               
               
                   
                 % ThO2 
               
               
                   
                 % CuO 
               
               
                   
                 % PbO 
               
               
                   
                 % Na2O 
               
               
                   
                 % SO4 
                 0.20 
               
               
                 filtercake 
                 % MoO2 
                 6.25 
                 0.47 
                 0.14 
                 0.16 
                 0.13 
                 0.18 
                 0.12 
                 7.11 
               
               
                 120° C. 
                 % MoO3 
                 81.56 
                 85.44 
                 89.18 
                 89.01 
                 88.47 
                 89.12 
                 89.28 
                 82.80 
               
               
                 filtrate 
                 Ag 
                 &lt;5 
                 &lt;5 
                 &lt;5 
                 &lt;5 
                 &lt;5 
                 &lt;5 
                 &lt;5 
                 &lt;5 
               
               
                 ICP 
                 Al 
                 407 
                 452 
                 405 
                 384 
                 413 
                 418 
                 422 
                 405 
               
               
                 analyses 
                 Ba 
                 &lt;1 
                 &lt;1 
                 &lt;1 
                 &lt;1 
                 &lt;1 
                 &lt;1 
                 &lt;1 
                 &lt;1 
               
               
                 mg/l 
                 Ca 
                 475 
                 527 
                 472 
                 445 
                 466 
                 479 
                 483 
                 470 
               
               
                   
                 Mg 
                 42 
                 46 
                 40 
                 37 
                 40 
                 42 
                 41 
                 40 
               
               
                   
                 Na 
                 38 
                 42 
                 36 
                 34 
                 35 
                 37 
                 38 
                 36 
               
               
                   
                 P 
                 &lt;50 
                 &lt;50 
                 &lt;50 
                 &lt;50 
                 &lt;50 
                 &lt;50 
                 &lt;50 
                 &lt;50 
               
               
                   
                 S 
                 58000 
                 65130 
                 59420 
                 55870 
                 59380 
                 59320 
                 59520 
                 59360 
               
               
                   
                 Sr 
                 19 
                 22 
                 20 
                 18 
                 20 
                 21 
                 20 
                 18 
               
               
                   
                 Cu 
                 759 
                 837 
                 747 
                 719 
                 759 
                 770 
                 782 
                 747 
               
               
                   
                 Fe 
                 1660 
                 1877 
                 1671 
                 1596 
                 1705 
                 1735 
                 1747 
                 1634 
               
               
                   
                 Mo 
                 17500 
                 24760 
                 28120 
                 30460 
                 24220 
                 20220 
                 21720 
                 21630 
               
               
                   
                 Pb 
                 &lt;10 
                 &lt;10 
                 &lt;10 
                 &lt;10 
                 &lt;10 
                 &lt;10 
                 &lt;10 
                 &lt;10 
               
               
                   
                 Ti 
                 27 
                 24 
                 24 
                 25 
                 23 
                 21 
                 22 
                 28 
               
               
                   
                 Zn 
                 17 
                 19 
                 18 
                 17 
                 17 
                 18 
                 18 
                 17 
               
               
                   
                 K 
                 162 
                 173 
                 141 
                 140 
                 161 
                 167 
                 189 
                 173 
               
               
                   
               
             
          
         
       
     
         [0027]    Keeping the concentration of HNO 3  fixed at 0.15 N and varying the concentration of H 2 SO 4  from 0.12 to 4 N, series of acidic solutions were prepared. Technical oxide was mixed in each of the solutions and the results of the leaching/oxidation with H 2 SO 4 /HNO 3  mixtures are summarized in Table 4. The dissolution of MoO 3  in varying concentrations of the acidic solution is shown in  FIG. 6 . Under these conditions, Ca and K dissolved only when the concentration of H 2 SO 4  was greater than 2 N. Al required concentrations greater than 4 N to dissolve. See  FIG. 7 . Fe and Ca dissolved readily in 0.1 N H 2 SO 4 . 
         [0000]    
       
         
               
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                   
                 TABLE 4 
               
               
                   
                   
               
               
                   
                 EX. 3A 
                 EX. 3B 
                 EX. 3C 
                 EX. 3D 
                 EX. 3E 
                 EX. 3F 
                 EX. 3G 
                 EX. 3H 
                 EX. 3I 
                 EX. 3J 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 Intake 
                 intake g 
                 75 
                 75 
                 75 
                 75 
                 75 
                 75 
                 75 
                 75 
                 75 
                 75 
               
               
                   
                 liquid ml 
                 250 
                 250 
                 250 
                 250 
                 250 
                 250 
                 250 
                 250 
                 250 
                 250 
               
               
                   
                 N H2SO4 
                 0.12 
                 0.25 
                 0.50 
                 1.00 
                 2.00 
                 4.00 
                 4.00 
                 4.00 
                 2.00 
                 2.00 
               
               
                   
                 ml H2SO4 96% 
                 0.80 
                 1.65 
                 3.30 
                 6.60 
                 13.50 
                 27.00 
                 27.00 
                 27.00 
                 13.50 
                 13.50 
               
               
                   
                 N HNO3 
                 0.15 
                 0.15 
                 0.15 
                 0.15 
                 0.15 
                 0.15 
                 0.25 
                 0.50 
                 0.25 
                 0.50 
               
               
                   
                 ml HNO3 65% 
                 2.60 
                 2.60 
                 2.60 
                 2.60 
                 2.60 
                 2.60 
                 5.20 
                 8.70 
                 5.20 
                 8.70 
               
               
                   
                 solids % 
               
               
                   
                 leaching 
                 70 
                 70 
                 70 
                 70 
                 70 
                 70 
                 70 
                 70 
                 70 
                 70 
               
               
                   
                 temp ° C. 
               
               
                   
                 leaching 
                 2 
                 2 
                 2 
                 2 
                 2 
                 2 
                 2 
                 2 
                 2 
                 2 
               
               
                   
                 time hrs 
               
             
          
           
               
                 flltercake 
                 % MgO 
                 &lt;0.1 
                 &lt;0.1 
                 &lt;0.1 
                 &lt;0.1 
                   
                   
                   
                   
                   
                   
                   
               
               
                 500° C. XRF 
                 % SiO2 
                 5.30 
                 4.60 
                 4.80 
                 4.50 
                 4.70 
                 5.50 
                 4.70 
                 6.20 
                 6.20 
                 5.50 
                 5.40 
               
               
                 method 
                 % K2O 
                 0.10 
                 0.20 
                 0.20 
                 0.20 
                 0.10 
                 &lt;0.1 
                 &lt;0.1 
                 — 
                 &lt;0.1 
                 &lt;0.1 
                 0.10 
               
               
                 Uniquant 
                 % CaO 
                 0.30 
                 0.20 
                 0.20 
                 0.20 
                 0.20 
                 0.10 
                 &lt;0.1 
                 &lt;0.1 
                 &lt;0.1 
                 0.10 
                 &lt;0.1 
               
               
                   
                 % Fe2O3 
                 0.90 
                 0.10 
                 0.10 
                 &lt;0.1 
                 &lt;0.1 
                 &lt;0.1 
                 &lt;0.1 
                 &lt;0.1 
                 &lt;0.1 
                 &lt;0.1 
                 &lt;0.1 
               
               
                   
                 % MoO3 
                 91.70 
                 94.30 
                 94.20 
                 94.50 
                 94.40 
                 93.70 
                 93.30 
                 93.10 
                 93.10 
                 93.70 
                 93.90 
               
               
                   
                 % CuO 
                 0.40 
               
               
                   
                 % PbO 
               
               
                   
                 % Na2O 
               
               
                   
                 % SO4 
                   
                   
                   
                   
                   
                   
                 0.50 
               
               
                 filtercake 
                 % MoO2 
                 6.53 
                 6.59 
                 6.32 
                 6.99 
                 6.68 
                 5.30 
                 2.60 
                 &lt;0.1 
                 0.20 
                 2.90 
                 2.60 
               
               
                 120° C. 
                 % MoO3 
                 83.15 
                 85.95 
                 85.54 
                 86.04 
                 85.64 
                 86.44 
                 88.14 
                 89.70 
                 89.30 
                 86.10 
                 87.50 
               
               
                 filtrate 
                 Al 
                   
                 363 
                 369 
                 408 
                 427 
                 545 
                 658 
               
               
                 ICP 
                 Ba 
               
               
                 analyses 
                 Ca 
                   
                 134 
                 146 
                 216 
                 217 
                 373 
                 411 
                 430 
                 422 
                 430 
                 440 
               
               
                 mg/l 
                 Mg 
                   
                 36 
                 36 
                 38 
                 34 
                 35 
                 33 
                 36 
                 36 
                 38 
                 39 
               
               
                   
                 Na 
                   
                 16 
                 15 
                 21 
                 28 
                 38 
                 36 
                 37 
                 36 
                 35 
                 36 
               
               
                   
                 P 
               
               
                   
                 S 
                   
                 1745 
                 3555 
                 7714 
                 14245 
                 28895 
                 57195 
                 63930 
                 61505 
                 28600 
                 29320 
               
               
                   
                 Sr 
                   
                 13 
                 13 
                 16 
                 14 
                 19 
                 16 
                 20 
                 20 
                 24 
                 25 
               
               
                   
                 Cu 
                   
                 714 
                 719 
                 801 
                 743 
                 793 
                 778 
                 859 
                 839 
                 792 
                 793 
               
               
                   
                 Fe 
                   
                 1544 
                 1549 
                 1698 
                 1571 
                 1652 
                 1613 
                 1763 
                 1739 
                 1694 
                 1696 
               
               
                   
                 Mo 
                   
                 3220 
                 3858 
                 6271 
                 11050 
                 22930 
                 31810 
                 36725 
                 32165 
                 21780 
                 25920 
               
               
                   
                 P 
                   
                 28 
                 27 
                 29 
                 24 
                 23 
                 25 
                 28 
                 27 
                 26 
                 25 
               
               
                   
                 Ti 
                   
                 1 
                 3 
                 5 
                 14 
                 22 
                 26 
                 24 
                 22 
                 18 
                 20 
               
               
                   
                 Zn 
                   
                 17 
                 17 
                 17 
                 16 
                 15 
                 14 
                 15 
                 15 
                 16 
                 17 
               
               
                   
                 K 
                   
                 6 
                 6 
                 16 
                 61 
                 101 
                 119 
                 121 
                 112 
                 91 
                 99 
               
               
                   
               
             
          
         
       
     
         [0028]    MoO 2  oxidized only when the concentration of H 2 SO 4  was greater than 2 N, and the oxidation was not always complete. See  FIG. 8 . Additional experiments were performed with 0.25 and 0.5 N HNO 3 . The results are summarized in  FIG. 8  and Table 4. 
       Sulfuric Acid/Hydrogen Peroxide: 
       [0029]    A series of acidic solutions were prepared with an H 2 SO 4  concentration of 4 N and varying concentrations of H 2 O 2 . The quantity of water was selected such that the total volume of acid, water and hydrogen peroxide equaled 250 ml. Hydrogen peroxide was slowly dropped into the reaction mass to control the vigorous reaction. The oxidation stoichiometry can be summarized as follows: 
         [0000]      2H 2 O 2 →O 2 (g)⇑2H 2 O 
         [0000]      2MoO 2 +O 2 →2MoO 3    
         [0030]    Because oxygen is lost, oxidation proceeds with a low efficiency, thus requiring excess H 2 O 2 . See  FIG. 9 . Addition of small amounts of nitric acid did not significantly increase oxidation efficiency. The results of the leaching/oxidation with H 2 SO 4 /H 2 O 2  mixtures are summarized in Table 5. 
         [0031]    Peroxide may also react directly with MoO 2  according to the following stoichiometry: 
         [0000]      MoO 2 +H 2 O 2 →H 2 MoO 4  (dissolved) or to MoO 3 +H 2 O 
         [0000]    followed by crystallization to H 2 MoO 4  or other MoO 3  solids. The reaction of MoO 2  with oxygen primarily occurs at autoclave conditions (temperatures above about 200° C.). 
         [0000]    
       
         
               
               
               
             
               
               
               
               
             
           
               
                   
                 TABLE 5 
               
               
                   
                   
               
               
                   
                 EX. 4A 
                 EX. 4B 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 intake 
                 intake g 
                 75 
                 75 
               
               
                   
                 liquid ml 
                 250 
                 250 
               
               
                   
                 N H2SO4 
                 4N 
                 4N 
               
               
                   
                 ml H2SO4 96% 
                 28.00 
                 28.00 
               
               
                   
                 N H2O2 
                 1.00 
                 0.25 
               
               
                   
                 ml H2O2 30% 
                 25.00 
                 6.25 
               
               
                   
                 solids % 
                 22.50 
               
               
                   
                 leaching temp ° C. 
                 70 
                 70 
               
               
                   
                 leaching time hrs 
                 2 
                 2 
               
               
                 filtercake 500° C. 
                 % MgO 
                   
                 &lt;0.1 
               
               
                 XRF method 
                 % SiO2 
                   
                 5.30 
               
               
                 Uniquant 
                 % K2O 
                   
                 &lt;0.1 
               
               
                   
                 % CaO 
                   
                 &lt;0.1 
               
               
                   
                 % Fe2O3 
                   
                 &lt;0.1 
               
               
                   
                 % MoO3 
                   
                 93.80 
               
               
                   
                 % CdO 
               
               
                   
                 % ThO2 
               
               
                   
                 % CuO 
               
               
                   
                 % PbO 
               
               
                   
                 % Na2O 
               
               
                   
                 % SO4 
                   
                 0.20 
               
               
                 filtercake 120° C. 
                 % MoO2 
                 6.60 
                 5.91 
               
               
                   
                 % MoO3 
                 82.60 
                 85.59 
               
               
                 filtrate ICP 
                 Ag 
               
               
                 analyses mg/l 
                 Al 
                   
                 532 
               
               
                   
                 Ba 
               
               
                   
                 Ca 
                   
                 400 
               
               
                   
                 Mg 
                   
                 32 
               
               
                   
                 Na 
                   
                 35 
               
               
                   
                 P 
               
               
                   
                 S 
                   
                 55740 
               
               
                   
                 Sr 
                   
                 16 
               
               
                   
                 Cu 
                   
                 737 
               
               
                   
                 Fe 
                   
                 1521 
               
               
                   
                 Mo 
                   
                 24075 
               
               
                   
                 Pb 
                   
                 30 
               
               
                   
                 Ti 
                   
                 25 
               
               
                   
                 Zn 
                   
                 15 
               
               
                   
                 K 
                   
                 116 
               
               
                   
               
             
          
         
       
     
       Sulfuric Acid/Potassium Permanganate: 
       [0032]    A series of acidic solutions were prepared with an H 2 SO 4  concentration of 4 N and varying concentrations of KMnO 4 . The oxidation stoichiometry is believed to proceed as follows: 
         [0000]      3MoO 2 +2MnO 4   − +2H + →3MoO 3 +2MnO 2 (s)+H 2 O 
         [0000]      2MnO 2 (S)+2MoO 2 +4H + →2MoO 3 +2Mn 2+ +2H 2 O 
         [0000]    With excess MnO 4   − : 
         [0000]      3Mn 2+ +2MnO 4   − +2H 2 O→5MnO 2 (s)+4H +   
         [0033]    The results of the leaching/oxidation with H 2 SO 4 /KMnO 4  mixtures are summarized in Table 6 and  FIG. 10 . 
         [0000]    
       
         
               
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                   
                 TABLE 6 
               
               
                   
                   
               
               
                   
                 EX. 5A 
                 EX. 5B 
                 EX. 5C 
                 EX. 5D 
                 EX. 5E 
                 EX. 5F 
                 EX. 5G 
                 EX. 5H 
                 EX. 5I 
                 EX. 5J 
               
               
                   
                 KMnO 4   
                 KMnO 4   
                 KMnO 4   
                 KMnO 4   
                 K 2 S 2 O 8   
                 K 2 S 2 O 8   
                 K 2 S 2 O 8   
                 K 2 S 2 O 8   
                 K 2 S 2 O 8   
                 K 2 S 2 O 8   
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 Intake 
                 intake g 
                 75 
                 75 
                 75 
                 75 
                 75 
                 75 
                 75 
                 75 
                 75 
                 75 
               
               
                   
                 liquid ml 
                 250 
                 250 
                 250 
                 250 
                 250 
                 250 
                 250 
                 250 
                 250 
                 250 
               
               
                   
                 N H2SO4 
                 4N 
                 4N 
                 4N 
                 4N 
                 4N 
                 4N 
                 4N 
                 2N 
                 2N 
                 2N 
               
               
                   
                 ml H2SO4 96% 
                 28.00 
                 28.00 
                 28.00 
                 28.00 
                 28.00 
                 28.00 
                 28.00 
                 13.50 
                 13.50 
                 13.50 
               
               
                   
                 mol KMnO4/ 
                 0.01 
                 0.02 
                 0.04 
                 0.05 
                 0.02 
                 0.04 
                 0.06 
                 0.02 
                 0.04 
                 0.06 
               
               
                   
                 KS2O8 
               
               
                   
                 g KMnO4/ 
                 1.55 
                 3.10 
                 6.25 
                 7.90 
                 4.60 
                 9.20 
                 13.80 
                 4.60 
                 9.20 
                 13.80 
               
               
                   
                 g K2S2O8 
               
               
                   
                 solids % 
                 22.50 
                 22.50 
                 22.50 
                 22.50 
                 22.50 
                 22.50 
                 22.50 
                 22.50 
                 22.50 
                 22.50 
               
               
                   
                 leaching 
                 70 
                 70 
                 70 
                 70 
                 70 
                 70 
                 70 
                 70 
                 70 
                 70 
               
               
                   
                 temp ° C. 
               
               
                   
                 leaching 
                 2 
                 2 
                 2 
                 2 
                 2 
                 2 
                 2 
                 2 
                 2 
                 2 
               
               
                   
                 time hrs 
               
               
                 filtercake 
                 % MgO 
                 &lt;0.1 
                 &lt;0.1 
                 &lt;0.1 
                 &lt;0.1 
                 &lt;0.1 
                 &lt;0.1 
                 &lt;0.1 
                 &lt;0.1 
                 &lt;0.1 
                 &lt;0.1 
               
               
                 500° C. 
                 % SiO2 
                 5.80 
                 5.70 
                 5.60 
                 4.80 
                 5.60 
                 6.20 
                 5.90 
                 4.40 
                 4.60 
                 4.70 
               
               
                 XRF 
                 % K2O 
                 0.20 
                 0.20 
                 0.80 
                 1.00 
                 0.20 
                 0.30 
                 0.40 
                 0.50 
                 0.90 
                 1.10 
               
               
                 method 
                 % CaO 
                 — 
                 &lt;0.1 
                 &lt;0.1 
                 &lt;0.1 
                 &lt;0.1 
                 &lt;0.1 
                 &lt;0.1 
                 0.10 
                 &lt;0.1 
                 &lt;0.1 
               
               
                 Uniquant 
                 % Fe2O3 
                 &lt;0.1 
                 &lt;0.1 
                 0.10 
                 0.10 
                 &lt;0.1 
                 &lt;0.1 
                 &lt;0.1 
                 &lt;0.1 
                 &lt;0.1 
                 &lt;0.1 
               
               
                   
                 % MoO3 
                 93.40 
                 93.40 
                 87.80 
                 86.60 
                 93.60 
                 93.00 
                 93.20 
                 94.00 
                 93.80 
                 92.70 
               
               
                   
                 % CdO 
               
               
                   
                 % ThO2 
               
               
                   
                 % CuO 
                 &lt;0.1 
                 &lt;0.1 
                 &lt;0.1 
                 &lt;0.1 
                 &lt;0.1 
                 &lt;0.1 
                 &lt;0.1 
                 &lt;0.1 
                 &lt;0.1 
                 &lt;0.1 
               
               
                   
                 % PbO 
               
               
                   
                 % Na2O 
               
               
                   
                 % SO4 
                   
                   
                 1.10 
                 1.70 
                   
                   
                   
                 &lt;0.1 
                 &lt;0.1 
                 0.10 
               
               
                   
                 % MnO2 
                 &lt;0.1 
                 &lt;0.1 
                 4.00 
                 5.20 
               
               
                 filtercake 
                 % MoO2 
                 2.60 
                 &lt;0.1 
                 0.25 
                 0.21 
                 4.40 
                 1.30 
                 0.20 
                 3.90 
                 1.60 
                 0.60 
               
               
                 120° C. 
                 % MoO3 
                 87.00 
                 89.70 
                 82.60 
                 82.70 
                 85.00 
                 88.10 
                 89.10 
                 85.70 
                 87.40 
                 87.90 
               
               
                 filtrate 
                 Al 
                   
                   
                   
                   
                   
                   
                   
                 371 
                 402 
                 366 
               
               
                 ICP 
                 Ba 
               
               
                 analyses 
                 Ca 
                 445 
                 449 
                 433 
                 432 
                 452 
                 444 
                 459 
                 313 
                 393 
                 417 
               
               
                 mg/l 
                 Mg 
                 38 
                 37 
                 37 
                 37 
                 40 
                 39 
                 40 
                 36 
                 40 
                 37 
               
               
                   
                 Na 
                 47 
                 49 
                 57 
                 60 
                 59 
                 70 
                 76 
                 49 
                 57 
                 56 
               
               
                   
                 S 
                 64730 
                 64580 
                 64370 
                 63430 
                 67900 
                 71400 
                 73315 
                 33150 
                 37045 
                 42760 
               
               
                   
                 Sr 
                 29 
                 33 
                 35 
                 35 
                 37 
                 40 
                 44 
                 20 
                 21 
                 23 
               
               
                   
                 Cu 
                 796 
                 795 
                 821 
                 780 
                 817 
                 774 
                 770 
                 775 
                 780 
                 755 
               
               
                   
                 Fe 
                 1734 
                 1736 
                 1642 
                 1643 
                 1711 
                 1647 
                 1632 
                 1653 
                 1682 
                 1635 
               
               
                   
                 Mo 
                 28160 
                 34560 
                 39255 
                 38190 
                 29110 
                 35950 
                 36890 
                 14210 
                 12580 
                 18165 
               
               
                   
                 P 
                 33 
                 22 
                 22 
                 22 
                 29 
                 24 
                 24 
               
               
                   
                 Ti 
                 24 
                 21 
                 21 
                 20 
                 26 
                 26 
                 25 
                 18 
                 16 
                 18 
               
               
                   
                 Zn 
                 16 
                 15 
                 14 
                 14 
                 16 
                 15 
                 15 
                 15 
                 14 
                 14 
               
               
                   
                 K 
                 1174 
                 1919 
                 3493 
                 4282 
                 3356 
                 6742 
                 10550 
                 3771 
                 7999 
                 11980 
               
               
                   
                 Mn 
                 2120 
                 4242 
                 98 
                 158 
                   
                   
                   
                 2 
                 2 
                 2 
               
               
                   
               
             
          
         
       
     
       Sulfuric Acid/Potassium Persulfate: 
       [0034]    A series of acidic solutions were prepared with an H 2 SO 4  concentration of 4 N and varying concentrations of KS 2 O 8 . The oxidation stoichiometry is believed to proceed as follows: 
         [0000]      MoO 2 +S 2 O 8   2− +H 2 O→MoO 3 +2SO 4   2− +2H +   
         [0000]    The results of the leaching/oxidation with H 2 SO 4 /KMnO 4  mixtures are summarized in Table 6 and  FIG. 10 . 
       Caro&#39;s Acid: 
       [0035]    Caro&#39;s acid is produced from concentrated sulfuric acid (usually 96-98%) and concentrated hydrogen peroxide (usually 60-70%), and comprises peroxymonosulfuric acid. Caro&#39;s acid is an equilibrium mixture having the following relationship: 
         [0000]      H 2 O 2 +H 2 SO 4 ⇄H 2 SO 5 +H 2 O 
         [0000]    The oxidation stoichiometry for MoO 2  in Caro&#39;s acid is believed to proceed as follows: 
         [0000]      MoO 2 +H 2 SO 5 →MoO 3 +H 2 SO 4    
         [0036]    75 grams of technical oxide was mixed with water and Caro&#39;s acid (H 2 SO 4 :H 2 O 2 =3:1, 2:1, and 1:1). In some embodiments, higher ratios may also be employed, such as 4:1 and 5:1. In separate experiments, the temperature of the reaction mass was either cooled or heated to T=25, 70 and 90° C. for and mixed for two hours. The results of the leaching/oxidation with Caro&#39;s acid mixtures are summarized in  FIG. 11 . 
       Chlorine, Chlorinated Compounds and Bromine: 
       [0037]    A three-necked jacketed 250 mL creased flask was used as the reactor. It was fitted with a ⅛″ Teflon feed tube (dip-tube) for chlorine addition, a condenser, a thermometer and a pH meter. The top of the condenser was connected with a T joint to a rubber bulb (as a pressure indicator) and to a caustic scrubber through a stop-cock and a knock-out pot. The flask was set on a magnetic stirrer. The jacket of the flask was connected to a circulating bath. Chlorine was fed from a lecture bottle set on a balance and a flow meter was used for controlling the chlorine feed. The lecture bottle was weighed before and after each experiment to determine the amount of chlorine charged. 
         [0038]    Technical oxide (50 g) was suspended in 95 g of water and/or recycled molybdenum solution from the ion-exchange step of previous experiments. Concentrated sulfuric acid was added in drops to bring the pH of the reaction mass down to 0.2 and the suspension was magnetically stirred. The suspension was heated to 60° C. using the circulating bath and stirred at that temperature for about 30 minutes. Chlorine was fed using a flow meter and bubbled through the suspension. The reaction was exothermic as indicated by the temperature increase to about 62° C. Chlorine feed was stopped when there was no more consumption of Cl 2  as indicated by an increase in pressure and drop in temperature to about 60° C. Stirring of the reaction mixture at 60° C. under slight chlorine pressure was continued for an hour to ensure complete oxidation. Nitrogen or air was then bubbled for 30 minutes to strip off unreacted chlorine. A 20% solution of NaOH was carefully added in drops to bring the pH up to 0.2. After pH adjustment, the mixture was stirred at 60° C. for an hour. It was then cooled to 30° C. and filtered using a fritted funnel (M) under suction. The solid on the funnel was washed with 25 g of 5% sulfuric acid and then with 25 g of water. The wet cake was weighed and then dried in an oven at 95° C. for about 15 hours. The filtrate was analyzed by ICP for molybdenum and other metals. The dried solid was analyzed by ICP for metal impurities. Some of the solid samples were also analyzed for the amount of MoO 2  and MoO 3 . 
         [0000]    Oxidation with Chlorine: 
       Example 1 
       [0039]    A 20 g sample of the technical oxide was suspended in 60 g of water. Concentrated sulfuric acid (10 g) was added and the mixture was heated to 60° C. After stirring the mixture for 30 minutes at 60° C., chlorine (3.6 g) was slowly bubbled through the mixture over a period of 40 minutes. The gray slurry became light green. The mixture was heated to 90° C.  and stirred at 90° C. for 30 minutes. Nitrogen was bubbled through the mixture at 90° C. for 30 minutes to strip off any unreacted chlorine. The mixture was cooled to room temperature. The slurry was then filtered under suction and washed with 20 g of 2% hydrochloric acid and 20 g of water. The wet cake (22.6 g) was dried in an oven at 90° C. for 15 hours to yield 16.8 g of product. 
         [0000]    Analysis of starting Tech. Oxide and Product by ICP: 
         [0000]    
       
         
               
               
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 MoO 3   
                 MoO 2   
                 Fe 
                 Cu 
                 Al 
               
               
                   
                 (wt %) 
                 (wt %) 
                 (ppm) 
                 (ppm) 
                 (ppm) 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 Starting Tech. Oxide 
                 70.8 
                 13.9 
                 13400 
                 15200 
                 3110 
               
               
                 Product 
                 90.6 
                 0.05 
                 457 
                 200 
                 233 
               
               
                   
               
             
          
         
       
     
       Example 2 
       [0040]    A slurry of 50 g of the same technical oxide used in Example 1 was formed in 95 g of water was stirred at 60° C. for 30 minutes. Chlorine (6.8 g) was bubbled through the slurry for about 40 minutes, maintaining a positive pressure of chlorine in the reactor. The slurry changed from gray to pale green. Nitrogen was bubbled for  30  minutes to strip off excess chlorine. Concentrated HNO 3  (5.0 g) was added dropwise to the mixture at 60° C. and stirred at 60° C. for 30 minutes after the addition. Then 20% NaOH solution was added to adjust the pH to 0.5. The mixture was cooled to 25° C. and filtered under suction. The wet cake (62.3 g) was dried in an oven at 90° C. for 16 hours to get 49.5 g of product. ICP analysis of the oxidized product showed that it contained 502 ppm Fe, 58 ppm Cu and 15 ppm Al. 
         [0000]    
       
         
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 Fe 
                 Cu 
                 Al 
               
               
                   
                 (ppm) 
                 (ppm) 
                 (ppm) 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Starting Tech. Oxide 
                 13400 
                 15200 
                 3110 
               
               
                   
                 Product 
                 502 
                 58 
                 15 
               
               
                   
                   
               
             
          
         
       
     
       Example 3 
       [0041]    Concentrated HCl (8.8 g) was added to a slurry of technical oxide (from a different source as compared to Examples 1 and 2) in 150 g of water to adjust the pH of the mixture to 0.4. The mixture was heated to 60° C. and stirred at that temperature for 30 minutes. Chlorine was slowly bubbled through the mixture till there was a positive pressure of chlorine in the reactor. It took 1.4 g of chlorine over a period of 35 minutes. The mixture was stirred at 60° C. for 30 minutes after chlorine addition and then nitrogen was bubbled through the mixture for 30 minutes. The liquid phase of the slurry had a pH of 0.4. The slurry was then cooled to room temperature and filtered under suction. The solid was washed with 25 g of 5 wt % HCl and 25 g of water. The wet cake (55.0 g) was dried in an oven at 90° C. for 16 hours to get 47.4 g of product. 
       Analysis of Starting Technical Oxide and Product by ICP: 
       [0042]      
         [0000]                                                                                  MoO 3     MoO 2     Fe   Cu   Al           (wt %)   (wt %)   (ppm)   (ppm)   (ppm)                                    Starting Tech. Oxide   90.8   4.30   7270   1700   1520       Product   97.07   0.03   526   29   37                    
Oxidation with Sodium Hypochlorite:
 
         [0043]    Technical oxide (20 g) was added to 45 g of water and 5 g of concentrated sulfuric acid taken in a jacketed 100 mL flask. The mixture was heated to 60° C. and magnetically stirred at that temperature for 30 minutes. Sodium hypochlorite solution (20 g) containing 10-13% active chlorine was taken in an addition funnel and added dropwise over 30 minutes. Color of the slurry changed from gray to blue to light green indicating complete oxidation. The liquid portion of the slurry had a pH of 0 as shown by pH paper. The mixture was cooled to room temperature and filtered under suction. The solid on the funnel was washed with 20 g of 5 wt % sulfuric acid and 20 g of water. The wet product (22.4 g) was dried in an oven at 90° C. for 16 hours to get 18.3 g of product. 
         [0000]    ICP analysis of Tech. Oxide and Product: 
         [0000]                                                                                  MoO 3     MoO 2     Fe   Cu   Al           (wt %)   (wt %)   (ppm)   (ppm)   (ppm)                                    Starting Tech. Oxide   70.8   13.9   13400   15200   3110       Product   91.2   0.05   520   180   54                    
Oxidation with Bromine:
 
         [0044]    A slurry of the same technical oxide from Examples 1 and 2 (40 g) in 120 g of water was taken in a 250 mL jacketed flask and stirred at 60° C. for 30 minutes. Bromine (10 g) taken in an addition funnel was slowly added in drops. Disappearance of the red color of bromine indicated reaction. Bromine addition took about 30 minutes. The mixture was heated to 90° C. and stirred at 90° C. for 30 minutes. Nitrogen was bubbled through the mixture at 90° C. for 30 minutes to strip off unreacted bromine. The mixture was cooled to room temperature and filtered under suction. The solid was washed with 20 g of 2 wt % HCl and 20 g of water. The wet cake (60.4 g) was dried at 90° C. for 16 hours to 38.6 g of product. The oxidized product had about 5000 ppm Fe, 600 ppm Cu and 200 ppm Al. 
         [0000]                                                                                  MoO 3     MoO 2     Fe   Cu   Al           (Wt %)   (Wt %)   (ppm)   (ppm)   (ppm)                                    Tech.. Oxide   70.8   13.9   13400   15200   3110       Product   87.12   0.10   5000   600   200                    
Oxidation with Sodium Chlorate:
 
         [0045]    Technical oxide (50 g) was mixed with 80 g of water and 5 g of concentrated sulfuric acid in a 250 mL jacketed flask and stirred at 60° C. for 30 minutes. Sodium chlorate (3 g) was dissolved in 15 g of water and the solution was taken in an addition funnel. The chlorate solution was slowly added in drops to the technical oxide slurry at 60° C. and the addition took about 30 minutes. Change in color of the slurry to light green indicated complete oxidation. The slurry was cooled to room temperature and filtered under suction. The solid was washed with 25 g of 2 wt % sulfuric acid and 25 g of water. The wet cake (65.4 g) was dried in an oven at 90° C. for 16 hours. Product (48.2 g) was analyzed by ICP for metallic impurities. 
         [0000]    
       
         
               
               
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 MoO 3   
                 MoO 2   
                 Fe 
                 Cu 
                 Al 
               
               
                   
                 (Wt %) 
                 (Wt %) 
                 (ppm) 
                 (ppm) 
                 (ppm) 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 Tech. Oxide 
                 70.8 
                 13.9 
                 13400 
                 15200 
                 3110 
               
               
                 Product 
                 85.80 
                 0.64 
                 2435 
                 639 
                 113 
               
               
                   
               
             
          
         
       
     
         [0046]    While the compositions and methods of this invention have been described in terms of distinct embodiments, it will be apparent to those of skill in the art that variations may be applied to the compositions, methods and/or processes and in the steps or in the sequence of steps of the methods described herein without departing from the concept and scope of the invention. More specifically, it will be apparent that certain agents, which are chemically related, may be substituted for the agents described herein while the same or similar results would be achieved. All such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the scope and concept of the invention.