Comprehensive recovery of flotation of a gold mine cyanide tailings

1 analysis of the influencing factors

1.1 Formation and influence of calcium peroxide film

Cyanide method for gold extraction, usually using lime as a "protective alkali", the pH value of the pulp is generally about 11, and in order to meet the needs of cyanide ratio, it is also necessary to press air, oxygen or peroxide into the slurry to improve the leaching rate of gold and silver. Such high alkalinity, oxygen enrichment and long-time immersion will form a hydrophilic calcium peroxide film (CaO2) on the surface of the ore particles, and the formation of this film is non-selective to the ore particles due to the ore particles in the slurry. The difference in surface electrical properties makes metal sulfide ore easier to form than non-metallic gangue minerals. The formation of a calcium peroxide film (CaO2) calcium peroxide film causes the collector to lose its selectivity for various minerals, and the film also hinders the adsorption of the collector and the surface of the ore.

Ca2++2OH→Ca(OH)2

Ca2++O2→CaO2

In order to remove the influence of the CaO2 film, it is often necessary to refine the water and reduce the pH to 8-9, and vigorously stir or even grind.

1.2 Cyanide immersion gold process is a strong oxidation process

Cyanide pulp must be strong alkaline pulp, pH=11, and often inflated into the slurry, even pure oxygen, or add strong oxidants, such as H2O2, CaO2, Na2O2, BaO2, etc., deoxygenation in cyanide tailings In the purification process, bleaching powder (CaOCl2), bleaching essence [Ca(OCl)2], and sodium hypochlorite (NaOCl) are often used to treat cyanide tailings to meet environmental protection requirements. These processes from leaching to sewage treatment are treated under high alkalinity and strong oxidizing conditions for up to two or thirty hours, which is a long process for recoverable sulphide ore in cyanide tailings. The strong oxidation process is sufficient to oxidize the surface, thereby reducing the floatability. Sometimes recovered by flotation pyrite have difficulty, because pyrite surface portion of the sulfur in the highly alkaline pulp into the free oxygen-rich conditions, generating further oxidation basic sulfate, ferric hydroxide generated the final film [Fe (OH ) 3] covered by the surface of the pyrite particles. Therefore, in order to eliminate such effects, it is often necessary to add a corresponding activator or re-grind to expose the fresh surface of the mineral.

1.3 Residual cyanide in cyanide tailings is a special inhibitor of sulfide ore flotation

Is well known, the lime is added cyanide sulfide flotation effects inhibitors, used to inhibit the pyrite, copper ore, the amount of a few grams to tens of grams, the amount of cyanide and cyanide leaching at least a few hundred grams / ton, many kilograms, such conditions, enough to suppress all sulphide ore. Therefore, when cyanide tailings flotation sulfide ore, the residual cyanide in cyanide tailings should be minimized, such as tailings pressure filtration, etc., and it is best to carry out comprehensive recovery after sewage treatment.

1.4 Cyanide salts in cyanide tailings are inhibitors of sulfide ore flotation

In the cyanidation process, the minerals associated with gold and silver mines also react with cyanide to form metal cyanide salts, which are strong inhibitors in the flotation of sulfide ore.

1.4.1 Iron minerals and sodium cyanide to form sodium thiocyanate

Pyrite: FeS2+NaCN==FeS+NaCNS

Pyrrhotite: Fe5S6+NaCN==NaCNS+5FeS

Ferrous sulfide: FeS+2O2==FeSO4FeSO4+6NaCN==Na4[Fe(CN)6]+Na2SO4

Metal iron filings: Fe+6NaCN+2H2O==Na4[Fe(CN)6]+2NaOH+H2↑

1.4.2 Copper minerals and sodium cyanide to form sodium copper cyanate

Cholesterol: 2CuSO4+4NaCN==Cu2(CN)2+2Na2SO4+(CN)2↑

Azurite: 2CuCO3+8NaCN==2Na2Cu(CN)3+2Na2CO3+(CN)2↑

Malachite: 2Cu(OH)2+8NaCN==2Na2Cu(CN)3+4NaOH+(CN)2↑

Copper ore: 2Cu2S+4NaCN+2H2O+O2==Cu2(CN)2+Cu2(CNS)2+4NaOH

1.4.3 Reaction of zinc mineral with sodium cyanide to form sodium zinc cyanate

Sphalerite: ZnS+4NaCN==Na2Zn(CN)4+Na2S

Zinc Oxide: ZnO+4NaCN+H2O==Na2Zn(CN)4+2NaOH

Zinc ore: ZnCO3+4NaCN==Na2Zn(CN)4+Na2CO3

Etc., these metal cyanide salts can form a hydrophilic film on the surface of the mineral and inhibit the adsorption of the xanthate molecule and be inhibited.

1.5 A large amount of metal ions remaining in the cyanide tailings consumption collector

A large amount of metal ions remain in the cyanide tailings, especially Ca2+, Fe2+, Cu2+, Zn2+.

The xanthate was discovered as early as 1782, but the earliest use of xanthate was chemical analysis. For example, the reaction of xanthate with copper salt to produce precipitation was used to quantitatively analyze copper. The presence of these metal ions has a catalytic effect on the decomposition of xanthate, and a large amount of poorly soluble metal salts of xanthate precipitates, which consumes a large amount of xanthate.

4ROCSSNa+2Me++==Me2(ROCSS)2↓+(ROCSS)2+2Na2SO4

Therefore, the cyanide tailings flotation method is comprehensively recovered, and the amount of the collector is usually large, which is why.

1.6 The large amount of salt produced during cyanidation deteriorates the flotation process

As mentioned above: a large amount of alkali and salts remain in the cyanide tailings, such as Ca(OH)2, CaO2, Fe(OH)3, Mem(CN)n, Ca(OCl)2, FeSO4, Na2S, Na2SO4 , Na2CO3, etc., the existence of a large number of these salts makes the chemical reaction process very complicated and difficult to predict. Because they contaminate the surface of the ore particles, the surface of the ore particles is unrecognizable, and the physical and chemical properties of the original surface are lost, which increases the difficulty of flotation separation.

1.7 The sludge generated by fine grinding cyanide consumes a large amount of flotation agent and destroys the selectivity of flotation

In order to increase the leaching rate of gold and silver, the mixing cyanide usually has a grinding fineness of 90%-200 mesh or 90%-325 mesh or more, so mineral mud is inevitably produced, and these slime not only adsorb on the surface of the ore. To make it lose its original surface properties. At the same time, a large amount of slime will adsorb a large amount of flotation agent due to its large specific surface area and surface energy, resulting in an increase in the amount of flotation agent.

2 Technical measures to improve the flotation effect of cyanide tailings

It can be seen from the above analysis that the technical route to improve the flotation effect of cyanide tailings should be carried out around drug removal and deliming.

2.1 mechanical drug removal, de-mud

The scrubbing machine is strongly stirred and scrubbed, the degreased bucket is dehydrated and degreased, and then further dehydrated and dehydrated by a filter press, and the flotation is re-pulled with water.

2.2 appropriate addition of drug removal

If adding appropriate amount of activated carbon to remove the drug, the removal of copper ions in cyanide tailings is better, but the amount of de-agent added must be controlled. Otherwise, the dosage will be too large, which will lead to a large increase in the amount of flotation agent.

2.3 Appropriate addition of slime dispersant

Adding water glass and carboxymethyl cellulose in an appropriate amount is very advantageous for improving the separation effect.

2.4 Re-grinding cyanide tailings

For cyanide tailings with coarser particle size, if economically reasonable, re-grinding flotation separation can be used for the purpose of comprehensive recovery.

2.5 using a selective collector

If the copper and sulfur are separated, choose Z-200.

2.6 appropriate amount of activator

In order to eliminate the influence of surface oxidation of the ore particles, an appropriate amount of activator is added, but a selective activator is used.

2.7 Use reselection preselection after tailing flotation

For low-grade cyanide tailings, the primary concentrating machine is used for the primary concentrating of the gangue, which can handle most of the gangue slime. Then flotation separation is carried out. Technically more reliable and economically more reasonable.

3Cyanide tailings lead copper and sulfur comprehensive recycling production application

The main metal minerals in cyanide tailings of a cyanide plant are pyrite, galena, chalcopyrite, and a small amount of pyrrhotite, magnetite, hematite, gangue minerals are mainly quartz , and A small amount of chlorite, kaolin, etc. Lead content is 19.95%; copper is 4.21%; gold is 5.00g/t; silver is 508.76g/t, sulfur is 37.50%.

The cyanide tailings of the plant are washed by three-stage countercurrent, concentrated by a thickener at a concentration of 55-60%, placed in a buffer stirred tank for high concentration for a long time (up to more than 1 hour), and scrubbed to remove the ore. The above various films on the surface are then preferentially selected into the flotation at a high concentration. The process makes full use of the residual C in cyanide tailings, cyanide and the like to inhibit pyrite, limonite and galena. The natural floatability reduces the process of re-slurrying and re-adding pyrite and chalcopyrite inhibitors, reducing production costs and simplifying the process. At the same time, high-concentration flotation is beneficial to the floating of large-scale lead ore, and at the same time enhances the scrubbing effect between the ore particles, which is beneficial to the surface of fresh ore particles and the collector. The chemical conditions were: dispersing agent 3000 g/t, inhibitor 80 g/t, diphtheria yellow drug 300 g/t, and No. 2 oil 120 g/t. pH = 10-11.

The floating lead tailings flow into the floating copper stirring tank by self-flow, and the copper flotation concentration is 30%. The process flow is a coarse, three-sweep, three-selection. The chemical conditions are: dispersing agent 1500g/t, Ding Huang Drug 1200g / t2 oil 200g / tpH = 10.

From the perspective of production sorting, the mineral processing technical indicators are ideal, the lead recovery rate is greater than 90%, the copper recovery rate is 53.92%, the total gold recovery rate (available) is 86%, and the total silver recovery rate (valuable) is 97.74%. Fully recovered gold, silver and lead, especially to compensate for the low recovery rate of silver cyanide. The sulfur concentrate contains more than 35% sulfur. However, due to the high content of metal ions in the backwater, the amount of collector is large, and there is still a need for further improvement.

4 Conclusion

(1) The technical point of the comprehensive recovery flotation of cyanide tailings is to remove various films on the surface of the ore particles, and also the minerals.

(2) In the flotation process of cyanide tailings, the use of dispersant is indispensable, but the dosage must be strictly controlled.

(3) It adopts lead, copper and sulfur priority flotation process, which is technically feasible and economically reasonable. It is an ideal process for flotation of cyanide tailings.

(4) Because the cyanide leaching slag has a fine particle size and a large slurry ratio, high concentration and fast flotation in the floating lead is beneficial to the recovery of lead.

(5) The comprehensive recovery of cyanide tailings will benefit the country and benefit the environment. The production practice of the plant proves that the comprehensive recovery of cyanide tailings is not only technically feasible, but also can earn more than 3 million yuan per year. It can also resettle more than 60 employees, and the economic and social benefits are very significant.

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