Flotation of gold-containing arsenic pyrite (3)
One author of this paper believes that under the conditions of flotation, the sulfide mineral is oxidized and a corresponding thiosulfate complex cation ( Me 2 S 2 O 3 ++ ) is formed on the surface . Its two positive charges are neutralized by hydroxide anions. In other words, the following reaction occurs on the surface of the oxidized sulfide mineral:
2MeS+2O 2 +H 2 O D Me 2 S 2 O 3 ( OH 2 ) Â Â Â ( 1 )
In the presence of a collector ( A '), an exchange occurs on the surface of the mineral, resulting in the formation of the corresponding compound, which is hydrophobic.
Me 2 S 2 O 3 ( OH ) 2 +
However, when the arsenic oxidation of pyrite, formed on the surface is not complex and hydroxide anion, but is a trivalent arsenic anions and.
2FeAsS+3.5O 2 D lFe 2 S 2 O 3 ( AsO 2 ) 2 Â Â Â ( 3 )
The anion of arsenic is replaced by hydroxide ions only when the solution alkalinity is continuously increased (see Figure 1 ).
Fe 2 S 2 O 3 ( AsO 2 ) 2 +2OH ′ D Fe 2 S 2 O 3 ( OH ) 2 +2AsO 2    ( 4 )
This means that not only hydroxide anions, but also trivalent arsenic anions can be used as collectors in the flotation of arsenopyrite.
FeS 2 O 3 ( AsO 2 ) 2 +
The test results show that when the pre-oxidized arsenopyrite is treated with butyl xanthate, arsenic can be precipitated in the solution.
Soda medium, with butyl xanthate ore - when starting stirring, the content of arsenic (mg / L) Growth follows:
                    Stir                        pH : 7.5                     pH : 10.5
                  (neutral medium)    (soda media)
   No added xanthate         1.2                               30
   After adding xanthate         1.2 ,      40
Therefore, only use a strong collector (this collector can have both hydrogen hydroxide and arsenic properties), or add arsenic that can be removed from the surface of the oxidized arsenopyrite. In the case of pharmaceuticals, effective flotation of arsenic pyrite can be achieved.
Soda solution has a great practical childlike meaning. If carbonate ions are present in the solution, arsenic can be removed from the surface of the arsenopyrite at a lower pH (see Table 1 ).
Since the oxidation of arsenopyrite in a closed mill depends on the amount of dissolved oxygen, the higher concentration of arsenic in the soda solution can only be the result of the exchange reaction.
Fe 2 S 2 O 3 ( AsO 2 ) 2 +CO 3 ′ D Fe 2 S 2 CO 3 +2AsO 2 '    ( 6 )
The interaction of arsenopyrite with the anion of the collector occurs over a wide pH range.
 Fe 2 S 2 O 3 CO 3 +
Therefore, under these conditions (as indicated by the test), the planktonic capacity of arsenopyrite will be significantly improved (see Figure 3 ).
Another reason for the good effect of soda is that the carbonate anion can both remove arsenic from the surface of the oxidized arsenopyrite and continue to react with the anion of the collector on the surface of the arsenopyrite.
Currently, the process of preparation of this system have been floating mineral slurry - seat using flotation concentrator with arsenic gold ore processing, resulting in the recovery of arsenopyrite increased by 13.2%, gold recovery increased by 5.5 % .
Knot    s
1. Soda has a good effect on the flotation of arsenic pyrite. The reason is that sodium carbonate is a resisting agent for metal iron oxidation, which can keep dissolved oxygen in a high concentration in the grinding circuit. This is necessary to oxidize the sulfide mineral prior to flotation of the sulfide mineral.
The carbonate anion removes arsenic from the surface of the oxidized arsenopyrite and continues to interact with the anion of the collector.
2. The above-mentioned pharmaceutical conditions for using the soda solution in the grinding circuit have been applied under industrial conditions, so that the process index of the gold selection plant is significantly improved.
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