Abstract:
An improvement in the froth flotation separation of metallic sulfide mineral ores, particularly those ores bearing copper and molybdenum, in which a mercaptan collector is used in an earlier primary flotation stage, the improvement comprising the addition of activated carbon to achieve deactivation of the mercaptan collector prior to the component mineral separation stage, thereby providing enhanced separation of the minerals.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation in part of copending application Ser. No. 934,132 now abandoned filed Aug. 15, 1978. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to an improvement in a froth flotation process for concentration and separation of metallic sulfide mineral ores. The improved process is directed to separations wherein a mercaptan is utilized as a collector in an earlier flotation stage. The improved method of this invention includes the addition of activated carbon to achieve deactivation of the mercaptan prior to a mineral separation stage and to achieve enhanced separation of the metallic elements desired. 
     Froth flotation is a process commonly employed for separating, collecting, and, hence, concentrating valuable minerals, particularly sulfide and oxide ores, from the gangue minerals associated with these minerals in their ores. The usual steps are as follows: 
     (a) The ore is crushed and subjected to wet grinding to provide a pulp wherein the ore particles are typically reduced to minus 48 mesh and with about 50% of the particles being in the minus 200 mesh fractions. 
     (b) The ore pulp is generally diluted with water to approximately 30% solids by weight. 
     (c) Various conditioning, collecting, and frothing agents are then added to the mineral pulp. 
     (d) The pulp is then aerated to produce air bubbles that rise to the surface of the pulp and to which the desired mineral particles selectively attach themselves by virtue of the characteristics of the collectors employed, thereby permitting removal of these minerals in a concentrated form. 
     There are, of course, numerous patents on processes for froth flotation concentration and separation of minerals. One such patent is U.S. Pat. No. 2,559,104 (issued July 3, 1951) to Arbiter et al which relates to a flotation recovery method for molybdenite. Arbiter et al teaches a specific system in which a collector is oxidized prior to subsequent separation stages. The problem addressed in the Arbiter et al patent involves reducing excess further and excess collector inthe subsequent cleaning stage. They tend to collect by virtue of the fact that the bulk of the collector and frother are carried forward into the next cleaning stage. In the Arbiter et al patent, reduction of the excess frother is accomplished by the addition of the activated carbon as required. 
     U.S. application Ser. No. 852,413, filed Nov. 17, 1977 by Adrian Wiechers, now U.S. Pat. No. 4,211,644 (the specification and claims of which are specifically incorporated herein by reference) teaches an improved process utilizing a mercaptan as a collector, the preferred mercaptan being normal dodecyl mercaptan (&#34;DDM&#34;). As will be seen hereinafter, the use of DDM increases the overall copper recovery from the ore, but at the same time can make separation of the copper from the molybdenite more difficult. 
    
    
     DRAWINGS 
     FIGS. 1 and 2 are general flowsheets illustrating treatment of ores from two different sources, Ore A in FIG. 1 and Ore B in FIG. 2. In each figure, the flowsheets compare the treatment steps and recovery percentages for a standard plant process of concentration and separation, a process employing DDM concentration and standard separation, and a process employing DDM concentration and the novel separation procedures of the present invention. 
    
    
     SUMMARY OF THE INVENTION 
     The improved process of this invention relates to the specific separation of metallic sulfide mineral ores comprising copper and molybdenum through flotation where an alkyl mercaptan has been used as a collector in an earlier flotation stage to provide a cleaner concentrate having the mercaptan present. The improvement in the process comprises deactivating the mercaptan, whereby the subsequent separation flotation stage is removed. The deactivation of the mercaptan is achieved by the addition of an effective amount of powdered activated carbon. 
     From the drawings, it is clear that an improvement in the overall yield of copper can be achieved by employing an alkyl mercaptan collector, 91.5% as compared to 90% in treatment of Ore A, and 89 to 89.7% as compared to 86.6% in treatment of Ore B. Unfortunately, 33.4% of the copper from Ore A and 67.4% of the copper from Ore B are carried into the molybdenum circuit when DDM is employed, as compared to 18.7% and 42.9%, respectively, for the previously employed standard plant procedure. Using the separation procedure of the present invention to deactivate the DDM prior to separation, only 8.2% of the copper in Ore A and 11.0% of the copper in Ore B are carried into the molybdenum circuit, providing a copper concentrate of 91.8% for Ore A and 89% for Ore B as compared to 81.3% and 57.1% for the standard plant process. 
     More specifically, the improved process is a method for recovery of metal values by froth flotation from metallic sulfide mineral ores comprising copper and molybdenum, including the steps of: 
     (A) forming an aqueous mineral pulp from the ore: 
     (B) subjecting the pulp to rougher flotation to provide a scavenger feed and a rougher concentrate: 
     (C) adding and effective amount of an alkyl mercaptan of the formula H n  H 2n+1  SH in which n is at least 12 to the primary flotation stages as a collector and subjecting the scavenger feed to flotation to provide a scavenger tailing and a scavenger concentrate; 
     (D) combining, regrinding, and cleaning the concentrates from the primary flotation stages (B) and (C) to provide a copper molybdenum cleaner concentrate; and then 
     (E) subjecting the cleaner concentrate of step (D) to component mineral stage flotation separation; the improvement which comprises deactivating substantial amount of the mercaptan collector on the mineral of the ore in the cleaner concentrate of step (D) prior to the component mineral stage flotation separation in step (E), said deactivating comprising adding a deactivating effective amount of activated carbon to the cleaner concentrate prior to flotation in step (E); to provide more effective mineral separation. 
     It is preferred that the activated carbon be added within the range of about 0.25 to about 1.0 pound of activated carbon per ton of initial ore feed and that it be added to the cleaner concentrate for a sufficient time interval prior to step (E) to provide substantial deactivation of the mercaptan prior to commencement of step (E). Such time interval is preferably within the range of about 5 to 30 minutes. 
     The invention is particularly applicable to copper-molybednum sulfide containing mineral ores and is quite suited to the typical type of Arizona porphyry ores. 
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The process of this invention involves subjecting the ore feed to primary grinding and then rougher flotation, including the addition of the appropriate reagents, to provide a feed to the scavenger flotation stage after which the rougher concentrate and the scavenger concentrate are combined, subjected to a regrinding, and then subjected to a number of cleaner flotation stages. Prior to commencement of the scavenger flotation stage, from about 0.005 to about 0.02 pounds per ton ore of a mercaptan (such as normal dodecyl mercaptan, &#34;DDM&#34;) is added as an auxiliary collector or promoter to provide increased metals recovery during the primary flotation stages. With certain sulfide minerals such as copper and molybdenum containing ores, the DDM produces undesirable effects in the subsequent separation stage. The process of this invention involves substantially deactivating the DDM prior to the mineral separation stage. 
     Ore Sample A 
     A representative ore sample which is the feed to a concentrator is obtained from a typical producing copper-molybdenum concentrator located in Arizona. Copper occurs predominately as chalcopyrite and molybdenum occurs primarily as molybdenite. 
     Distribution data for the ore sample show that the copper values are approximately equally distributed on all size fractions from 65- to plus 400-mesh with a high distribution of copper (47%) in the minus 400-mesh (37 micrometers). A relatively constant distribution of molybdenum occurs in the coarser size fractions while 67% reports to the minus 400-mesh fraction. The copper and molybdenum minerals are liberated at a relatively coarse mesh of grind. 
     The assays of the three concentrator cyclone overflow samples utilized in the examples are as follows: 
     
                       TABLE 1______________________________________  Assay, %  Direct        Calculated.sup.1  Cu      Mo        Cu        Mo______________________________________Sample 3 0.39      0.014     0.38    0.014Sample 4 0.37      0.018     0.38    0.017Sample 5 0.35      0.003     0.34    0.003______________________________________ .sup.1 Average assay as calculated from tests 
    
     Standard conditions and reagent balance is shown in Table 2. The reagent balance is substantially identical to that of current conventional plant practice. 
     
                                           TABLE 2__________________________________________________________________________Test Conditions and Reagent BalanceFeed - 4000 grams dry solids cyclone overflow pulp sample__________________________________________________________________________    Reagents Added, lb/Ton of Ore.sup.1                        Time                   Shell                        MinutesStage    CaO   Z-6.sup.3              AF-238.sup.4                   1638.sup.5                        Cond                            Froth                                pH__________________________________________________________________________Condition    1.0                 1       11.0Rougher        0.01              0.005                   0.03 1   5Scavenger               0.01 1   5   10.7Thicken.sup.2Regrind  0.25                101st cleaner             0.005                        1   3   11.22nd cleaner    0.10                1   3   11.23rd cleaner    0.10                1   2   11.2              NaCN/    (NH).sub.4 S.sub.2          NaSH              ZnSO.sub.4Condition 1    11.0                10Condition 2    25.0          5Mo rougher                       3   9.3Mo 1st cleaner 5.0           5   3Mo 2nd cleaner     2.0       3   2   9.0__________________________________________________________________________ .sup.1 Reagent additions based on lb/ton of ore with exception of (NH.sub.4 ).sub.2 S, NaSH, and NaCN/ZnSO additions which are based on lb/ton Cu--Mo cleaner concentrate. .sup.2 Combine rougher and scavenger concentrates. Thicken to approximately 60% solids. .sup.3 Potassium amyl xanthate .sup.4 Sodium di secondary butyl dithiophosphate .sup.5 85% methyl isobutyl carbinol, 15% distillate bottoms 
    
     The most desirable, readily available activated carbon useful in deactivating the mercaptan collector is of a relatively high pore surface area of about 0.95 ml per gram and is a lignite-based powdered activated carbon. ICI type GFP is particularly useful. 
     Activated carbon addition is made prior to the sulfidizing reagent addition in the copper-molybdenum separation and about 10 minutes allowed for conditioning. 
     Summarized in Table 3 are the comparative results illustrating the significant improvement in deactivating the mercaptan collector (DDM) with the addition of activated carbon, while the effect of varying levels of activated carbon is illustrated by the results shown in Table 4. 
     
                                           TABLE 3__________________________________________________________________________Comparison of Effect of General Cu--Mo Separation ProcessesFeed                   Weight     Distribution,Sample                 Percent                       Assay, %                             % OverallNo. Process  Product   Overall                       Cu Mo Cu  Mo__________________________________________________________________________2   Standard-plant        Mo Ro Conc                  0.20 27.9                          1.48                             18.7                                 38.8    (no DDM) Cu Conc   0.75 26.2                          0.07                             66.0                                 7.0        Cu + Mo Cl Conc                  0.95 26.6                          0.37                             84.7                                 45.72   Standard-plant*        Mo Ro Conc                  0.40 25.1                          0.86                             33.4                                 43.9        Cu Conc   0.65 24.3                          0.06                             52.6                                 4.9        Cu + Mo Cl Conc                  1.05 24.6                          0.36                             86.0                                 48.84   Standard-plant*        Mo Ro Conc                  0.37 25.7                          1.19                             26.3                                 36.0        Cu Conc   0.74 23.8                          0.04                             54.2                                 2.3        Cu + Mo Cl Conc                  1.11 26.2                          0.40                             80.5                                 38.33   Activated carbon*        Mo Ro Conc                  0.20 19.5                          2.23                             10.0                                 32.9    (1.0 lb/ton ore)        Cu Conc   1.06 26.0                          0.05                             71.3                                 3.9        Cu + Mo Cl Conc                  1.26 25.0                          0.40                             81.3                                 36.8__________________________________________________________________________ *0.0075 pound of DDM addition per ton of ore feed to the scavenger flotation stage 
    
     
                                           TABLE 4__________________________________________________________________________Effect of Varying Level of Activated Carbon on Cu--Mo Separation    Activated                    Distribution,Sample    Carbon          Weight                    Assay, %                            % OverallNo. lb/Ton Ore     Product   Percent                    Cu  Mo  Cu  Mo__________________________________________________________________________2   --     Mo Ro Conc               0.40 25.1                        0.86                            33.4                                43.9     Cu Conc   0.65 24.3                        0.059                            52.6                                4.9     Cu + Mo Cl Conc               1.05 24.6                        0.36                            86.0                                48.84   --    Mo Ro Conc               0.37 25.7                        1.19                            26.3                                36.0     Cu Conc   0.74 23.8                        0.035                            54.2                                2.3     Cu + Mo Cl Conc               1.11 26.2                        0.40                            80.5                                38.34   0.25  Mo Ro Conc               0.23 19.9                        1.84                            13.6                                23.3     Cu Conc   0.88 26.0                        0.041                            67.6                                2.0     Cu + Mo Cl Conc               1.11 24.7                        0.41                            81.2                                25.33   0.50  Mo Ro Conc               0.22 24.0                        2.27                            13.9                                35.4     Cu Conc   0.94 27.0                        0.060                            67.1                                4.0     Cu + Mo Cl Conc               1.15 26.7                        0.48                            81.0                                39.43   1.0   Mo Ro Conc               0.20 19.5                        2.23                            10.0                                32.9     Cu Conc   1.06 26.0                        0.050                            71.3                                3.9     Cu + Mo Cl Conc               1.26 25.0                        0.40                            81.3                                36.84   1.35  Mo Ro Conc               0.20 15.7                        2.06                            10.9                                24.3     Cu Conc   0.86 24.4                        0.14                            73.3                                7.1     Cu + Mo Cl Conc               1.06 22.8                        0.50                            84.2                                31.44   2.0   Mo Ro Conc               0.18 17.7                        1.24                            8.9 12.2     Cu Conc   1.07 24.2                        0.31                            72.7                                18.2     Cu + Mo Cl Conc               1.25 23.2                        0.44                            81.6                                30.4__________________________________________________________________________ 
    
     The results indicate that 0.25 to 0.50 pound activated carbon per ton ore is sufficient to reduce the copper displacement in the molybdenum circuit to approximately 13% from approximately 30% without activated carbon. Increasing the activated carbon level to one pound per ton ore result in only a marginal further decrease of copper loss in the molybdenum circuit to about 10%. 
     Increasing the activated carbon level to greater than one pound per ton of ore does not appear to significantly reduce copper loss to the molybdenum circuit, but it may result in reduced molybdenum recovery to the molybdenum rougher concentrate. 
     A similar series of experiments were conducted on another typical copper molybdenum ore from a different location in Arizona, designated for convenience, as Ore B. These experiments developed the data for Tables 5 through 9. 
     Table 5 contains the head assay, Table 6 sets forth the reagent balance, and Table 7 the copper-molybdenum separation reagent balance for the Ore B experiments. Table 8 shows that using activated carbon in the process of the present invention, the copper concentrate contains 92.5% of the copper as compared with 57.1% for the standard plant process and 32.6% for DDM with the standard separation process. Table 9 shows the effect of varying levels of activated carbon, while Table 10 illustrates the wise variety of activated carbons which can be employed. 
     
                       TABLE 5______________________________________Head Assays - Ore B      Assay, %      Direct      Calculated.sup.1        Cu       Mo       Cu     Mo______________________________________Sample 1(HRI No. T-229)        0.70     0.015    0.69   0.015Sample 2(HRI No. T-236)        0.72     0.018    0.73   0.018______________________________________ .sup.1 Average head assays as calculated from all tests 
    
     
         Additional assays were performed on the Sample 1 headsample. The results are shown below.      Assay, %        Non-     Non-        Sulfide  Sulfide        Cu.sup.1 Mo       Fe     S (Total)______________________________________Sample 1     0.060    &lt;0.001   3.05   1.77______________________________________ .sup.1 Assay confirmed by two analysts 
    
     
                                           TABLE 6__________________________________________________________________________Reagent Balance - Ore B   Reagents Added, lb/Ton Ore                       Time,           Fuel        MinutesStage   CaO Sm-8.sup.1           Oil.sup.2               Z-11.sup.3                   MIBC.sup.4                       Cond                           Froth                               pH__________________________________________________________________________Primary grind   1.2 0.015           0.025   0.05                       --  --Rougher                     --  6   10.0Scavenger           0.003                   0.01                       1   6   9.7Thicken.sup.5               --  --Regrind 0.2     0.01        --  --1st cleaner             0.005                       1   4   10.02nd cleaner                 1   3   9.2Stage   Rougher-scavenger                   1st, 2nd cleanerEquipment   Denver D-1, 1000 g cell                   Denver D-1, 250 g cellSpeed, rpm   1900            1200Airflow, l/min   ˜16       ˜6% solids   35              15__________________________________________________________________________ .sup.1 Minerec Sm8 .sup.2 Fuel oil  50:50 mixture No. 2 diesel oil/kerosene .sup.3 Sodium ethyl xanthate .sup.4 MIBC  85% methyl iosbutyl carbinol/15% MIBC distillation bottoms .sup.5 Thickened rougherscavenger concentrate to approximately 60% solids decanted (reclaim) water used as makeup in cleaner stages 
    
     
                                           TABLE 7__________________________________________________________________________Copper-Molybdenum Separation Reagent Balance   Reagents Added, lb/Ton Concentrate Feed                                   Time,        NaCN    Na-Ferro                     K-Ferri       MinutesStage   H.sub.2 SO.sub.4.sup.1        ZnO.sup.2            H.sub.2 O.sub.2.sup.3                CN   CN   NaOCl.sup.4                               MIBC                                   Cond                                       Froth                                           pH__________________________________________________________________________Condition 1   0.50 0.46            --  --   --   --   --  20  --  8.7-6.7Condition 2   0.20 --  3.75                --   --   --   --  20  --  6.9-6.6Mo rougher   0.20 --  --  2.0  --   --   0.004                                   1   4   7.0Mo 1st cleaner   --   --  --  1.0  --   --   0.003                                   1   3   7.4Mo 2nd cleaner   --   --  --  --   0.20 1.0  --  1   3   7.6Mo 3rd cleaner   --   --  --  --   0.10 --   0.02                                   1   2   7.7Mo 4th cleaner   --   --  --  --   0.10 --   0.02                                   1   2   7.8Mo 5th cleaner   --   --  --  --   0.10 --   0.01                                   1   2   8.0Mo 6th cleaner   --   --  --  --   0.10 --   0.01                                   1    11/2                                           8.1Condition 1, 2 - pulp density 50% solidsMo rougher - pulp density 20% solids__________________________________________________________________________ .sup.1 Addition based on pounds 100% H.sub.2 SO.sub.4 .sup.2 NaCN/ZnO  5:1 mixture .sup.3 30% H.sub.2 O.sub.2? .sup.4 5% available Cl 
    
     
                                           TABLE 8__________________________________________________________________________Comparing Cu/Mo Separation With and Without DDM and Activated Carbon              Weight                  Assay, %                          Distribution, %Conditions Product %   Cu  Mo  Cu  Mo__________________________________________________________________________Standard separation      Mo Cl Conc              1.68                  13.3                      19.6                          0.8 51.5on concentrate with-out DDM    Mo Ro Conc              35.81                  31.6                      1.61                          42.9                              90.7      Cu Conc 64.19                  23.4                      0.09                          57.1                              9.3      Head (calc)              100.00                  26.3                      0.64                          100.0                              100.0Standard separation      Mo Cl Conc              8.74                  28.9                      5.80                          9.5 82.8on concentrate withDDM        Mo Ro Conc              57.39                  31.3                      1.02                          67.4                              95.4      Cu Conc 42.61                  20.4                      0.067                          32.6                              4.6      Head (calc)              100.00                  26.7                      0.61                          100.0                              100.0DDM plus 0.6 lbs/      Mo Cl Conc              0.91                  13.8                      33.7                          0.5 57.8ton ore activatedcarbon     Mo Ro Conc              6.78                  28.0                      7.04                          7.5 89.8      Cu Conc 93.22                  25.1                      0.058                          92.5                              10.2      Head (calc)              100.00                  25.3                      0.53                          100.0                              100.0__________________________________________________________________________ 
    
     
                                           TABLE 9__________________________________________________________________________Effect of Varying Level of Activated Carbon in Ore B Experiments              Weight                  Assay, % Distribution, %Conditions     Product  %   Cu  Mo   Cu  Mo__________________________________________________________________________Standard, no acti-     Mo 3rd Cl conc              8.74                  28.9                      5.80 9.5 82.8vated carbon     Mo Ro conc              57.38                  31.3                      1.02 67.4                               95.4     Cu conc  42.61                  20.4                      0.067                           32.6                               4.6     Head (calc)              100.00                  26.7                      0.61 100.0                               100.00.075 lb activated     Mo 3rd Cl conc              9.23                  29.2                      5.30 10.8                               81.3carbon/ton ore     Mo Ro conc              38.21                  30.8                      1.46 47.5                               93.8(1.37 lb/ton conc)     Cu conc  61.79                  21.0                      0.059                           52.5                               6.2     Head (calc)              100.00                  24.8                      0.60 100.0                               100.00.15 lb activated     Mo 3rd Cl conc              3.66                  26.4                      12.0 3.9 76.5carbon/ton ore     Mo Ro conc              23.84                  30.6                      2.20 29.5                               91.5(2.73 lb/ton conc)     Cu conc  76.16                  22.8                      0.064                           70.5                               8.5     Head (calc)              100.00                  24.7                      0.57 100.0                               100.00.30 lb activated     Mo 3rd Cl conc              2.74                  21.2                      16.1 2.4 74.7carbon/ton ore     Mo Ro conc              16.80                  28.9                      3.18 19.8                               90.5(5.45 lb/ton conc)     Cu conc  83.20                  23.7                      0.068                           80.2                               9.5     Head (calc)              100.00                  24.6                      0.59 100.0                               100.00.60 lb activated     Mo 3rd Cl conc              1.77                  13.7                      23.5 1.0 69.8carbon/ton ore     Mo Ro conc              10.73                  26.6                      4.98 11.6                               89.5(10.91 lb/ton conc)     Cu conc  89.27                  24.4                      0.070                           88.4                               10.5     Head (calc)              100.00                  24.6                      0.60 100.0                               100.00.90 lb activated     Mo 3rd Cl conc              2.60                  18.5                      15.5 2.0 75.1carbon/ton ore     Mo Ro conc              11.47                  26.9                      4.17 12.6                               89.2(16.38 lb/ton conc)     Cu conc  88.53                  24.2                      0.066                           87.4                               10.8     Head (calc)              100.00                  24.5                      0.54 100.0                               100.01.25 lb activated     Mo 3rd Cl conc              2.06                  11.5                      21.7 1.0 70.4carbon/ton ore     Mo Ro conc              10.86                  24.8                      5.41 11.0                               92.6(22.75/ton conc)     Cu conc  89.14                  24.5                      0.052                           89.0                               7.4     Head (calc)              100.00                  24.5                      0.63 100.0                               100.0__________________________________________________________________________ 
    
     
                                           TABLE 10__________________________________________________________________________Effect of Type of Activated Carbon (0.6 Pounds Per Ton Ore)              Weight                  Assay, % Distribution, %Activated Carbon      Product %   Cu  Mo   Cu  Mo__________________________________________________________________________Darco-GFP  Mo 2nd Cl conc              0.91                  13.8                      33.7 0.5 57.8      Mo Ro conc              6.78                  28.0                      7.04 7.5 89.8      Cu conc 93.22                  25.1                      0.058                           92.5                               10.2      Head (calc)              100.00                  25.3                      0.53 100.0                               100.0Darco-FM-1 Mo 3rd Cl conc              1.16                  10.5                      28.4 0.5 67.1      Mo Ro conc              7.30                  26.2                      6.17 7.5 91.7      Cu conc 92.70                  25.4                      0.044                           92.5                               8.3      Head (calc)              100.00                  25.5                      0.49 100.0                               100.0Calgon-PCB Mo 3rd Cl conc              2.57                  18.3                      17.0 1.9 78.4      Mo Ro conc              13.13                  28.6                      3.99 15.0                               93.9      Cu conc 86.87                  24.8                      0.039                           85.0                               6.1      Head (calc)              100.00                  25.3                      0.56 100.0                               100.0Union Carbide-LCK      Mo 3rd Cl conc              2.40                  14.0                      18.5 1.3 74.0      Mo Ro conc              11.70                  27.6                      4.75 12.8                               92.6      Cu conc 88.30                  25.0                      0.050                           87.2                               7.4      Head (calc)              100.00                  25.3                      0.60 100.0                               100.0Norit-RO 0.8      Mo 3rd Cl conc              1.33                  5.52                      31.3 0.3 67.5      Mo Ro conc              10.80                  26.4                      5.35 11.2                               93.7      Cu conc 89.20                  25.4                      0.043                           88.8                               6.3      Head (calc)              100.00                  25.5                      0.61 100.0                               100.0Sethco-powdered      Mo 3rd Cl conc              4.30                  23.1                      9.92 3.9 76.9      Mo Ro conc              18.00                  29.8                      2.85 21.0                               92.3      Cu conc 82.00                  24.5                      0.052                           79.0                               7.7      Head (calc)              100.00                  25.4                      0.56 100.0                               100.0__________________________________________________________________________ 
    
     Reference was made hereinbefore to U.S. Pat. No. 2,559,104 to Arbiter et al which teaches the oxidizing of a collector prior to the subsequent separation stages, and the use of activated carbon to reduce excess frother and excess collector in the subsequent cleaning stages. While apparently similar to the process of the present invention, the chemical route taught by Arbiter et al is, in fact, exactly opposite to that employed in the process of the present invention. Thus while Arbiter et al teaches the use of an oxidizing agent to deactivate the collector, the process of the present invention employes activated carbon to deactivate the collector, and there is strong evidence that in so doing, the activated carbon acts as a reducing agent. 
     Measurements were made of the oxidation-reduction potential (emf) of the pulp just prior to molybdenum rougher flotation. These measurements were made at various levels of activated carbon and the results are set forth in Table 11. 
     
                       TABLE 11______________________________________Pounds Activated Carbon                Pulp emf,Per Ton Ore          -mv______________________________________0.00                 3800.075                3601.15                 3000.30                 2600.60                 1900.90                 1801.25                 170______________________________________ 
    
     In addition, it has been found that sodium zinc cyanide, which was heretofore considered to be an essential reagent to the process, can be omitted. A further series of tests were conducted in which the emf was measured on a series of pulps wherein the sodium zinc cyanide was omitted, the level of activated carbon was maintained constant, and only the conditioning time was varied. The data developed in these further tests are set forth in Table 12, while the distribution of copper and molybdenum is described in Table 13. 
     
                       TABLE 12______________________________________0.60 lb Activated Carbon                Pulp emf,/Ton Ore             -mv______________________________________(20 minute A.C. cond time)                160(10 minute A.C. cond time)                190( 5 minute A.C. cond time)                230______________________________________ 
    
     
                                           TABLE 13__________________________________________________________________________Effect of Elimination of Sodium Zinc Cyanide              Weight                  Assay, % Distribution, %Condition  Product %   Cu  Mo   Cu  Mo__________________________________________________________________________Standard, with      Mo 3rd Cl conc              1.77                  13.7                      23.5 1.0 69.8NaZnCN 0.60 lb A.C.      Mo Ro conc              10.73                  26.6                      4.98 11.6                               89.5/ton ore to Cond 1      Cu conc 89.27                  24.4                      0.070                           88.4                               10.5      Head (calc)              100.00                  24.6                      0.60 100.0                               100.00.60 lb A.C./ton ore      Mo 3rd Cl conc              1.13                  12.7                      29.7 0.6 65.8No NaZnCn  Mo Ro conc              9.03                  29.7                      5.10 10.4                               90.2      Cu conc 90.97                  25.3                      0.055                           89.6                               9.8      Head (calc)              100.00                  25.7                      0.51 100.0                               100.0No activated carbon      Mo Ro Conc              45.97                  30.2                      1.38 54.3                               96.4No NaZnCN  Cu conc 54.03                  21.6                      0.044                           45.7                               3.6      Head (calc)              100.00                  25.6                      0.66 100.0                               100.0__________________________________________________________________________ 
    
     The data in Tables 11 and 12 clearly indicate that as the level of activated carbon increased, and/or as the conditioning time increased for a fixed level of carbon, the emf of the pulp decreased. In other words, the net effect of the treatment with activated carbon was to achieve a reduction reaction as evidenced by these substantially lower emf measurements. 
     Though not willing to be bound by any one theory by which the functioning of the activated carbon might be explained, at least one possible mechanism is that the activated carbon functions by desorption of oxygen from the collector-mineral surface bond to render a given sulfide mineral hydrophillic. Desorption of the oxygen from the sulfide minerals surface would render collector inactive, and therefore, the mineral particle hydrophillic. In a copper molybdenum separation, the action of the activated carbon is apparently specific to copper and iron sulfide minerals rendering these less floatable than the molybdenite, while it very surprisingly does not appear to cause desorption of oxygen and/or collector from the molybdenite surface and the molybdenite, therefore, continues to be hydrophobic. 
     It will, of course, be obvious to those skilled in the art, that many changes and substitutions can be made in the specific materials, reactants, and procedural steps set forth hereinbefore, without departing from the scope of the present invention, and it is my intention to be limited only by the appended claims.