Collector agent for the recovery of metal values in sulphide ores by froth flotation
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: 
     
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gasoline         20% to 45% by weight                                     
MIBC              5% to 15% by weight                                     
EEF              50% to 75% by weight                                     
S                 0% to  2% by weight                                     
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     and preferably within the following ranges: 
     
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gasoline         20% to 40% by weight                                     
MIBC              5% to 10% by weight                                     
EEF              50% to 70% by weight                                     
S                 0% to  2% by weight                                     
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     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. 
     
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MIBC:                                                                     
              ##STR1##                                                    
EEF:         mixture of:                                                  
             Diethyl xanthogenformiate                                    
              ##STR2##                                                    
             Diethyl xanthic oxide                                        
              ##STR3##                                                    
             Ethyl Alcohol                                                
             C.sub.2 H.sub.5 OH                                           
Sulphur:     S°                                                    
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     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: 
     
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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)                                 
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     Ores containing zinc, such as: 
     Sphalerite--(ZnS) 
     Ores containing lead, such as: 
     Galena--(PbS) 
     Ores containing silver, such as: 
     
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Argentite           (Ag.sub.2 S)                                          
Stephanite          (Ag.sub.5 Sb S.sub.4)                                 
Pyrargyrite         (Ag.sub.3 Sb S.sub.3)                                 
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     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: 
     
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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)                             
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     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): 
     
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1st agitation        5 min minimum                                        
2nd agitation        5 min minimum                                        
settling time       20 min minimum                                        
Total reaction time 30 min minimum                                        
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     (B) For a Full Plant preparation with amounts up to 100,000 liters: 
     
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1st agitation       15 min minimum                                        
2nd agitation       15 min minimum                                        
settling time       60 min minimum                                        
Total reaction time 90 min minimum                                        
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     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: 
     
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Mixture of hydrocarbon                                                    
                     30% by weight                                        
MIBC                 10% by weight                                        
EEF                  60% by weight                                        
S                     0%                                                  
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     More specifically, the best known proportions for the ingredients of this reagent are as follows: 
     
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Mixture of hydrocarbons                                                   
                     30.00% by weight                                     
MIBC                 10.00% by weight                                     
Diethyl xanthogenformiate                                                 
                     46.20% by weight                                     
Diethyl xanthic oxide                                                     
                      7.62% by weight                                     
Ethyl alcohol         3.00% by weight                                     
Others                3.18% by weight                                     
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     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: 
     
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 Diethyl xanthogenformiate                                                
 ##STR4##               77.0% by weight                                   
Diethyl xanthic oxide                                                     
 ##STR5##               12.7% by weight                                   
Ethyl alcohol                                                             
C.sub.2 H.sub.5OH       5.0% by weight                                    
other                   5.3% by weight                                    
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     III. MIBC: 
     
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 ##STR6##              100.0% by weight                                   
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     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: 
     
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Minerals          % Weight                                                
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Pyrite            4.40                                                    
Chalcopyrite      0.97                                                    
Chalcocite        0.52                                                    
Covelline         0.61                                                    
Bornite           0.19                                                    
Tennantite        Tr.                                                     
Molybdenum        0.03                                                    
Gangue            93.24                                                   
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% sulfide copper  1.27                                                    
% oxide copper    0.18                                                    
% total copper (head)                                                     
                  1.45                                                    
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     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: 
     
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Hydrocarbons         0.021 grams                                          
MIBC                 0.007 grams                                          
EEF                  0.042 grams                                          
S                    0.000                                                
Total                0.070 grams                                          
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     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: 
     
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Hydrocarbons         0.015 grams                                          
MIBC                 0.005 grams                                          
EEF                  0.030 grams                                          
S                    0.000                                                
Total                0.050 grams                                          
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     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                                                     
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                Ex. 1  Ex. 2    Ex. 3                                     
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Heads     % total Cu  1.380    1.420  1.404                               
Concentrates                                                              
          % total Cu  12.70    17.70  17.90                               
          % insoluble 27.80    18.80  17.40                               
Tails     % total Cu  0.224    0.204  0.204                               
Recovery  % total Cu  85.29    86.62  86.47                               
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     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: 
     
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Minerals              % Weight                                            
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Pyrite                0.96                                                
Chalcopyrite          2.11                                                
Chalcocite            0.38                                                
Covelline             0.56                                                
Bornite               traces                                              
Tennantite            traces                                              
Tetrahedrite          traces                                              
Molybdenum            0.03                                                
Gangue                95.96                                               
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% sulfide copper      1.40                                                
% oxide copper        0.20                                                
% total copper        1.60                                                
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     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                                                    
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                Ex. 4  Ex. 5    Ex. 6                                     
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Heads     % total Cu  1.679    1.688  1.677                               
Concentrates                                                              
          % total Cu  18.30    21.80  22.00                               
          % insoluble 30.40    24.30  26.00                               
Tails     % total Cu  0.200    0.192  0.204                               
Recovery  % total Cu  89.04    89.40  88.67                               
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     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: 
     
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Hydrocarbons       20.70 grams/TM                                         
MIBC                6.90 grams/TM                                         
EEF                41.40 grams/TM                                         
S                  00.00 grams/TM                                         
Total              69.00 grams/TM                                         
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     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                                                   
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                Example 7                                                 
                Collector                                                 
                         Example 8                                        
                Agent of Standard                                         
                this Invention                                            
                         Collector EEF                                    
                69 g/TM  84 g/TM                                          
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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       4.47                                     
Concentrates                                                              
         %Cu (Total)  8.11       8.84                                     
         %MoS.sub.2   0.15       0.15                                     
         %Fe (Total)  10.53      11.07                                    
         %Insol.      45.36      44.40                                    
Tails    %Cu (Total)  0.202      0.210                                    
         %Cu (non-sulfur)                                                 
                      0.09       0.09                                     
         %MoS.sub.2 0.010                                                 
                      0.013                                               
         %Fe (Total)  3.13       3.20                                     
Recovery %Cu (Total)  88.01      87.02                                    
         %Cu (non-sulfur)                                                 
                      61.42      56.03                                    
         %MoS.sub.2   67.14      64.69                                    
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     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: 
     
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Hydrocarbons       22.50 grams/TM                                         
MIBC                7.50 grams/TM                                         
EEF                45.00 grams/TM                                         
S                   0.00 grams/TM                                         
Total              75.00 grams/TM                                         
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     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                                                    
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                 Collector                                                
                 of this Standard                                         
                 invention                                                
                         collector EEF                                    
                 75 g/TM 80 g/TM                                          
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Head      % Cu (Total) 1.58      1.47                                     
          % Cu (non-sulfur)                                               
                       0.19      0.18                                     
          % MoS.sub.2  0.036     0.033                                    
Concentrate                                                               
          % Cu (Total) 24.67     20.95                                    
(Rougher and                                                              
          % MoS.sub.2  0.47      0.36                                     
Upgrader) % Insol.     15.28     19.60                                    
General Mill                                                              
          % Cu (Total) 0.236     0.218                                    
Tails (Rougher                                                            
          % MoS.sub.2  0.012     0.014                                    
and Upgrader)                                                             
          % Insol.     0.053     0.100                                    
Recovery  % Cu (Total) 85.87     86.11                                    
(Rougher and                                                              
Upgrader)                                                                 
Final Copper                                                              
          % Cu (Total) 42.03     38.27                                    
Concentrate                                                               
          % MoS.sub.2  0.20      0.23                                     
          % Insol.     4.30      6.52                                     
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