Abstract:
A collector agent for use in froth flotation processes to recover metal values of sulphide ores is disclosed which agent comprises the reaction product resulting from mixing and reacting in the presence of visible light, heat, or both, a mixture of: 
     (i) a mixture of hydrocarbons having from 5 to 10 (inclusive) carbon atoms, 
     (ii) methyl isobutyl carbinol (MIBC), 
     (iii) ethyl xanthyl ethylformic ester (EEF), and 
     (iv) elemental sulphur (S).

Description:
PRIOR ART 
     The use of ethyl xanthyl ethylformic ester (EEF) as a collecting agent in the froth flotation method of recovering metal values of sulphide ores is known. Such processes commonly use a frothing agent or &#34;frother&#34; and may also use a modifier such as sulphuric acid or calcium hydroxide. 
     BRIEF DESCRIPTION OF THE INVENTION 
     In the present invention the collector agent comprises the reaction product of a mixture of: 
     (i) a mixture of aliphatic, napthenic, and aromatic hydrocarbons having from 5 to 10 (inclusive) carbon atoms, 
     (ii) methyl isobutyl carbinol (MIBC), 
     (iii) ethyl xanthyl ethylformic ester (EEF), and 
     (iv) elemental sulfur (S). 
     The reaction is carried out in the presence of visible light, heat, or both. The proportions may vary within the following limits: 
     
         ______________________________________gasoline         20% to 45% by weightMIBC              5% to 15% by weightEEF              50% to 75% by weightS                 0% to  2% by weight______________________________________ 
    
     and preferably within the following ranges: 
     
         ______________________________________gasoline         20% to 40% by weightMIBC              5% to 10% by weightEEF              50% to 70% by weightS                 0% to  2% by weight______________________________________ 
    
     When this mixture reacts, a green colored reagent is produced, which turns into a dark brown compound when exposed to light or heat, with improvement in its collecting properties. The mixture shows a low flash point requiring the use of suitable safety precautions as will be apparent to those skilled in the art. 
     The chemical formulas of the compounds of this collector agent are: 
     Mixture of hydrocarbons with not less than five nor more than ten carbon atoms: 
     This is a commercially available product named gasoline and tends to vary somewhat. However, generally it has the following makeup: 
     (a) 48% by weight of aliphatic hydrocarbons, including oleffins (10%) and paraffins (38% ). Specifically, by weight: 
      3%--C 6  H 12   
      3%--C 7  H 14   
      4%--C 8  H 16   
     18%--C 5  H 12   
     10%--C 6  H 14   
     10%--C 7  H 16   
     (b) 20% by weight of naphthenic hydrocarbons 
     20%--C 7  H 14   
     (c) 30% by weight of aromatic hydrocarbons 
     15% toluene--C 7  H 8   
     10% orthoxylene--C 8  H 10   
      5% methaxylene--C 8  H 10   
     (d) 2% by weight of N, O, S and other. 
     
         ______________________________________MIBC:         ##STR1##EEF:         mixture of:        Diethyl xanthogenformiate         ##STR2##        Diethyl xanthic oxide         ##STR3##        Ethyl Alcohol        C.sub.2 H.sub.5 OHSulphur:     S°______________________________________ 
    
     The collector of this invention works efficiently in a flotation circuit of acid pH or with a natural water-mineral pH less than 7, and is particularly suited for the froth flotation of metallic ores comprising metallic sulphides such as: 
     Ores containing copper and iron such as: 
     
         ______________________________________Chalcopyrite        (CuFeS.sub.2)Chalcocite          (Cu.sub.2 S)Covelline           (CuS)Bornite             (Cu.sub.5 FeS.sub.4)Tennantite          (Cu.sub.12 AS.sub.4 S.sub.13)Tetrahedrite        (Cu.sub.12 Sb.sub.4 S.sub.13)Pyrite              (FeS.sub.2)Enargite            (Cu.sub.3 AS S.sub.4)______________________________________ 
    
     Ores containing zinc, such as: 
     Sphalerite--(ZnS) 
     Ores containing lead, such as: 
     Galena--(PbS) 
     Ores containing silver, such as: 
     
         ______________________________________Argentite           (Ag.sub.2 S)Stephanite          (Ag.sub.5 Sb S.sub.4)Pyrargyrite         (Ag.sub.3 Sb S.sub.3)______________________________________ 
    
     Ores containing platinum, such as: 
     Cooperite--Pt(AsS) 2   
     The collector agent is also suitable for the froth flotation of metallic ores of copper sulphide containing also low amounts of copper oxide such as: 
     
         ______________________________________Cuprite            (Cu.sub.2 O)Brochantite        (Cu.sub.4 (SO.sub.4)(OH).sub.6)Malachite          (CU.sub.2 (OH).sub.2 CO.sub.3)Chrysocolla        (CuSiO.sub.3 -2 H.sub.2 O)______________________________________ 
    
     Metallic ores of copper sulphide which also contain molybdenite (MoS 2 ) can also be treated successfully. 
     Sulphide ores of cobalt, nickel, tin and other metallic sulphides can also be processed with the collector of this invention. 
     In the selective flotation of one or more of copper, iron, or molybdenum ores, the collector can be added in the grinding stage at rates of about 70 grams per metric ton (g/TM) for head grades varying between 1.40 and 1.60% copper, with a corresponding increase or decrease in rate as indicated by variations in the head grade of the useful element. 
     Flotation with the collector of this invention includes the use of a frothing reagent which is added independently, either in the grinding stage or in conditioner tanks or boxes ahead of the flotation stage, but does not include necessarily the use of a modifier such as sulfuric acid or calcium hydroxide. 
     It has been found that the collector agent of this invention has better solubility in water than EEF, and that it has the further advantage of lower cost by approximately 30% with respect to the standard reagent EEF. 
     Further, the collector agent of this invention improves its selectivity and efficiency in the stages following flotation such as up-grading, cleaning and recleaning of concentrates and does not require the use of secondary collectors or accelerators. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Preparation of the Reagent 
     The reagent of this invention is prepared by adding the mixture of hydrocarbons to the EEF and agitating the same. After agitation the MIBC is added to the mixture and the mixture is again agitated. After the second agitation the mixture is left to settle in the presence of light. The time for agitation and settling needed to complete the reaction is variable depending upon the amount of reagent being prepared but the time is not proportional necessarily to the quantity of reagent and depends in part upon the reactor equipment used. The following times are illustrative. 
     (A) For a laboratory preparation (For example 2,000 cc): 
     
         ______________________________________1st agitation        5 min minimum2nd agitation        5 min minimumsettling time       20 min minimumTotal reaction time 30 min minimum______________________________________ 
    
     (B) For a Full Plant preparation with amounts up to 100,000 liters: 
     
         ______________________________________1st agitation       15 min minimum2nd agitation       15 min minimumsettling time       60 min minimumTotal reaction time 90 min minimum______________________________________ 
    
     The preparation temperature used in preparing a reagent for the following examples was 15° C.; however, a range of about 4° C. to about 20° C. is satisfactory. 
     The preferred quantities of the ingredients in this mixture are as follows: 
     
         ______________________________________Mixture of hydrocarbon                30% by weightMIBC                 10% by weightEEF                  60% by weightS                     0%______________________________________ 
    
     More specifically, the best known proportions for the ingredients of this reagent are as follows: 
     
         ______________________________________Mixture of hydrocarbons                30.00% by weightMIBC                 10.00% by weightDiethyl xanthogenformiate                46.20% by weightDiethyl xanthic oxide                 7.62% by weightEthyl alcohol         3.00% by weightOthers                3.18% by weight______________________________________ 
    
     In the examples below the specific quantities of ingredients used in each example are set forth therein. The preparation procedure followed was that set forth above under &#34;Preparation of the Reagent&#34; and the specific chemical makeup of the ingredients was as follows: 
     I. The mixture of hydrocarbons* had the following makeup: 
    
     (a) 48% by weight of aliphatic hydrocarbons, including oleffins (10%) and paraffins (38%). Specifically, 
      3% C 6  H 12  by weight 
      3% C 7  H 14  &#34;&#34; 
      4% C 8  H 16  &#34;&#34; 
     18% C 5  H 12  &#34;&#34; 
     10% C 6  H 14  &#34;&#34; 
     10% C 7  H 16  &#34;&#34; 
     (b) 20% by weight of naphthenic hydrocarbons 
     20% C 7  H 14   
     (c) 30% by weight of aromatic hydrocarbons 
     15% toluene--C 7  H  8   
     10% orthoxylene--C 8  H 10   
      5% methaxylene--C 8  H 10   
     (d) 2% by weight of N, O, S and other. 
     II. The EEF ingredient had the following components: 
     
         ______________________________________ Diethyl xanthogenformiate ##STR4##               77.0% by weightDiethyl xanthic oxide ##STR5##               12.7% by weightEthyl alcoholC.sub.2 H.sub.5OH       5.0% by weightother                   5.3% by weight______________________________________ 
    
     III. MIBC: 
     
         ______________________________________ ##STR6##              100.0% by weight______________________________________ 
    
     IV. Elemental sulfur may be added to stabilize the reagent and is, therefore, optional. 
     EXAMPLE #1 (Laboratory Scale) 
     Tests were conducted on ores coming from the Mine Teniente 1 Sur whose characteristics and ore composition are as follows: 
     
         ______________________________________Minerals          % Weight______________________________________Pyrite            4.40Chalcopyrite      0.97Chalcocite        0.52Covelline         0.61Bornite           0.19Tennantite        Tr.Molybdenum        0.03Gangue            93.24______________________________________% sulfide copper  1.27% oxide copper    0.18% total copper (head)             1.45______________________________________ 
    
     The ore (quartz-sericite) shows considerable variation with the presence of clay of up to 4% by weight. 
     The ore was crushed to -10 mesh and ground wet in a ball mill at a concentration of 67% solids until a grind of 80% minus 150 mesh was obtained. Flotations at acid conditions with an initial density of 34% solids were carried out in a laboratory flotation machine (WEMCO) at 1700 rpm. 
     The standard collector EEF was added to the above ore in the ball mill at the rate of 70 grams per metric ton (g/TM); frother Dow-froth 1012 and sulfuric acid as modifier were used. Frother and modifier were added to the flotation cell and agitated for 30 seconds. Flotation was carried out for 7 minutes. 
     EXAMPLE #2 (Laboratory Scale) 
     The collector reagent of this invention was prepared as above described. The ingredients had the following proportions: 
     
         ______________________________________Hydrocarbons         0.021 gramsMIBC                 0.007 gramsEEF                  0.042 gramsS                    0.000Total                0.070 grams______________________________________ 
    
     The reagent was added in the ball mill to the same ore as in Example 1 instead of the standard collector EEF. The reagent was added at the rate of 70 g/TM. Other conditions were as in Example 1. 
     EXAMPLE #3 (Laboratory Scale) 
     The collector reagent of this invention was prepared as above described. The ingredients had the following proportions: 
     
         ______________________________________Hydrocarbons         0.015 gramsMIBC                 0.005 gramsEEF                  0.030 gramsS                    0.000Total                0.050 grams______________________________________ 
    
     The reagent was added in the ball mill at the rate of 50 g/TM to the same ore as in Examples 1 and 2. Other conditions were as in examples 1 and 2. 
     The results of Examples 1, 2, and 3 are set forth in Table I below. 
     
                       TABLE I______________________________________           Ex. 1  Ex. 2    Ex. 3______________________________________Heads     % total Cu  1.380    1.420  1.404Concentrates     % total Cu  12.70    17.70  17.90     % insoluble 27.80    18.80  17.40Tails     % total Cu  0.224    0.204  0.204Recovery  % total Cu  85.29    86.62  86.47______________________________________ 
    
     The above results show that the collector reagent of this invention gives a clear advantage over the standard EEF, with a higher concentrate grade, lower insoluble content and higher copper recovery. 
     EXAMPLE #4 (Laboratory Scale) 
     This test was carried out with ores coming from the Mine Tenient Norte, whose characteristics and minerological compositions are different from those of Example #1 and are set forth below: 
     
         ______________________________________Minerals              % Weight______________________________________Pyrite                0.96Chalcopyrite          2.11Chalcocite            0.38Covelline             0.56Bornite               tracesTennantite            tracesTetrahedrite          tracesMolybdenum            0.03Gangue                95.96______________________________________% sulfide copper      1.40% oxide copper        0.20% total copper        1.60______________________________________ 
    
     This ore does not contain clay and is less varied than the ore from Teniente 1 Sur. The crushing, grinding and flotation stages were as in the previous examples. 
     The standard collector EEF was added to the ore in the ball mill at the rate of 70 g/TM; Dow-Froth 1012 was added as a frother and sulfuric acid as modifier was also used. Frother and modifier were conditioned for 30 seconds. Flotation was carried out for 7 minutes. 
     EXAMPLE #5 
     The collector reagent of this invention prepared as above described and having the same proportions as Example #2 was added in the ball mill to the same ore as in Example #4 at the rate of 70 g/TM instead of the standard collector. Other conditions were as in Example #4. 
     EXAMPLE #6 
     The collector reagent of this invention prepared as above described and having the same proportions as Example #3 was added at the rate of 50 g/TM in the ball mill to the same ore as in Examples #4 and #5 instead of the standard collector. Other conditions were as in Examples 4 and 5. 
     The results of Examples 4, 5 and 6 are set forth in Table II below: 
     
                       TABLE II______________________________________           Ex. 4  Ex. 5    Ex. 6______________________________________Heads     % total Cu  1.679    1.688  1.677Concentrates     % total Cu  18.30    21.80  22.00     % insoluble 30.40    24.30  26.00Tails     % total Cu  0.200    0.192  0.204Recovery  % total Cu  89.04    89.40  88.67______________________________________ 
    
     The results of Examples 4 through 6 show that the collector reagent of this invention gives better concentrate grades and less insoluble content than the standard EEF. Recoveries are higher in Example 5 and lower in Example 6 with respect to the standard, but the difference is not significant. 
     EXAMPLES 7 and 8 (Industrial Scale, pilot section) 
     The first industrial scale test was carried out in the Colon Concentrator of Codelco Chile-Division El Teniente. 
     One plant section, with a capacity of 4000 TM/d was fed with the collector reagent of this invention at the rate of 69 g/TM of dry ore. The proportions of the ingredients of the reagent prepared as above described were: 
     
         ______________________________________Hydrocarbons       20.70 grams/TMMIBC                6.90 grams/TMEEF                41.40 grams/TMS                  00.00 grams/TMTotal              69.00 grams/TM______________________________________ 
    
     A comparison was made with one plant section of similar capacity that was fed the standard collector EEF at the rate of 84 g/TM of dry ore. In both sections similar rates of frother Dowfroth 1012 and sulfuric acid were fed. The results of Examples 7 and 8 are set forth in Table III. 
     
                       TABLE III______________________________________           Example 7           Collector                    Example 8           Agent of Standard           this Invention                    Collector EEF           69 g/TM  84 g/TM______________________________________Head     %Cu (Total)  1.414      1.393    %Cu (non-sulfur)                 0.19       0.18    %MoS.sub.2   0.027      0.031    %Fe (Total)  4.37       4.47Concentrates    %Cu (Total)  8.11       8.84    %MoS.sub.2   0.15       0.15    %Fe (Total)  10.53      11.07    %Insol.      45.36      44.40Tails    %Cu (Total)  0.202      0.210    %Cu (non-sulfur)                 0.09       0.09    %MoS.sub.2 0.010                 0.013    %Fe (Total)  3.13       3.20Recovery %Cu (Total)  88.01      87.02    %Cu (non-sulfur)                 61.42      56.03    %MoS.sub.2   67.14      64.69______________________________________ 
    
     The results of these plant tests show advantages in recovery using the collector reagent of this invention in spite of a lower addition rate than the standard collector. 
     Concentrate grades do not show significant difference. 
     EXAMPLES 9 and 10 (Industrial scale, full plant) 
     The Colon Concentrator of Codelco Chile-Division El Teniente, whose rated capacity is 25,000 TM/d, was operated using as reagent the collector reagent of this invention. The reagent prepared as above described was added at the rate of 75 g/TM. The ingredients had the following proportions: 
     
         ______________________________________Hydrocarbons       22.50 grams/TMMIBC                7.50 grams/TMEEF                45.00 grams/TMS                   0.00 grams/TMTotal              75.00 grams/TM______________________________________ 
    
     The plant results were compared with those obtained using the standard collector at the rate of 80 g/TM. 
     The results of Examples 11 and 12 are set forth in Table IV and show the effects on the final products obtained during the test runs. These results clearly indicate the advantages offered by the collector reagent of this invention because of its positive influence on selectivity in the cleaning and recleaning circuits. 
     
                       TABLE IV______________________________________            Collector            of this Standard            invention                    collector EEF            75 g/TM 80 g/TM______________________________________Head      % Cu (Total) 1.58      1.47     % Cu (non-sulfur)                  0.19      0.18     % MoS.sub.2  0.036     0.033Concentrate     % Cu (Total) 24.67     20.95(Rougher and     % MoS.sub.2  0.47      0.36Upgrader) % Insol.     15.28     19.60General Mill     % Cu (Total) 0.236     0.218Tails (Rougher     % MoS.sub.2  0.012     0.014and Upgrader)     % Insol.     0.053     0.100Recovery  % Cu (Total) 85.87     86.11(Rougher andUpgrader)Final Copper     % Cu (Total) 42.03     38.27Concentrate     % MoS.sub.2  0.20      0.23     % Insol.     4.30      6.52______________________________________