Li Xinmin Zhang Zhanliang Li Ping Zhang Caimin
Luonan County of Shaanxi Province Chen Gold Smelting Co., Ltd.
Xie Jianhong Zhang Zhiyuan
School of Materials and Engineering, Xi'an University of Architecture and Technology
  Pick  want  In this paper, combined with the phenomenon of comprehensive recovery of useful minerals in cyanide tailings, the factors affecting the recovery effect are theoretically analyzed and explained, which has certain guiding significance for the design of mineral processing technology and production practice.
Key words  Cyanide tailings flotation comprehensive recovery influencing factors production practice Â
In recent years, in order to make full use of the country's precious mineral resources, reduce environmental pollution, and also increase the economic benefits of enterprises, many factories and mines have paid attention to the comprehensive recovery of useful minerals in cyanide leach residue, and their beneficiation process has been re-elected. Flotation, magnetic separation, re-floating combined processes, etc. The flotation recovery process for the purpose of sulfide ore accounts for a large proportion, among which there are many factories and mines that have been successfully recovered, but the recovery effect of factories and mines is not satisfactory. This paper analyzes and discusses the theory in this way and finds out the main effects affecting the recycling effect. The reason is to take corresponding contingency measures, aiming at guiding the production and providing a reference for theoretical analysis and process design for decision makers and scientists.
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, long time soaking will
A hydrophilic calcium peroxide film (CaO 2 ) is formed on the surface of the ore particles, and the formation of the film is non-selective to the ore particles. The metal sulfide ore ratio is different due to the difference in surface electrical properties of the ore particles in the slurry. Non-metallic gangue minerals are easier to form. The formation of a calcium peroxide film (CaO 2 ) 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.
Ca 2+ +2OH→Ca(OH) 2
Ca 2+ +O 2 →CaO 2
In order to remove the influence of the CaO 2 film, it is often necessary to refine the water and reduce the pH to 8-9, and vigorously stir or even grind.
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1.2 Cyanide immersion gold process is a strong oxidation process
Cyanide pulp must be a strong alkaline pulp, pH = 11 or so, and often inflated into the slurry, even pure oxygen, or add strong oxidants, such as H 2 O 2 , CaO 2 , Na 2 O 2 , BaO 2, etc. Etc. In the deoxygenation purification process of cyanide tailings, bleaching powder (CaOCl 2 ), bleaching essence [Ca(OCl) 2 ], 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 ) Covers 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, more than 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 process of cyanidation, the minerals associated with gold and silver mines also react with cyanide to form metal cyanide salts, which are just vulcanized.
A powerful inhibitor during mine flotation.
1.4.1 Iron minerals and sodium cyanide to form sodium thiocyanate
Pyrite: FeS 2 +NaCN==Fe S+NaCNS
Pyrrhotite: Fe 5 S 6 +NaCN==NaCNS+5FeS
Ferrous sulfide: Fe S+2O 2 ==FeSO 4 FeSO 4 +6NaCN==Na 4 [Fe(CN) 6 ]+Na 2 SO 4
Metal iron filings: Fe+6NaCN+2H 2 O==Na 4 [Fe(CN) 6 ]+2NaOH+H 2 ↑
1.4.2 Copper minerals and sodium cyanide to form sodium copper cyanate
Cholesterol: 2CuSO 4 +4NaCN==Cu 2 (CN) 2 +2Na 2 SO 4 +(CN) 2 ↑
Azurite: 2CuCO 3 +8NaCN==2Na 2 Cu(CN) 3 +2Na 2 CO 3 +(CN) 2 ↑
Malachite: 2Cu(OH) 2 +8NaCN==2Na 2 Cu(CN) 3 +4NaOH+(CN) 2 ↑
Chalcopyrite: 2Cu 2 S+4NaCN+2H 2 O+O 2 ==Cu 2 (CN) 2 +Cu 2 (CNS) 2 +4NaOH
1.4.3 Reaction of zinc mineral with sodium cyanide to form sodium zinc cyanate
Sphalerite: ZnS+4NaCN==Na 2 Zn(CN) 4 +Na 2 S
Zinc Oxide: ZnO+4NaCN+H 2 O==Na 2 Zn(CN)4+2NaOH
Zinc ore: ZnCO 3 +4NaCN==Na 2 Zn(CN) 4 +Na 2 CO 3
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.
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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 Ca 2+ , Fe 2+ , Cu 2+ , Zn 2+ . The results of the determination of the relevant ion concentration in the lean liquid of a cyanide plant are shown in Table 1.
Table 1 Analysis results of ion composition of a poor liquid in a cyanide plant
ingredient | Free cyanide | Total cyanide | Thiocyanate | Cu | Pb | Zn | Fe | PH |
Content (mg/l) | 637.07 | 1592.69 | 3150.00 | 1190.00 | 1630.00 | 1340.00 | 200.00 | 11 |
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 ++ ==Me 2 (ROCSS) 2 ↓+(ROCSS) 2 +2Na 2 SO 4
     2ROCSSNa+1/2O 2 +CO 2 ==(ROCSS)2+Na 2 CO 3
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 , CaO 2 , Fe(OH) 3 ,
Me m (CN) n , Ca(OCl) 2 , FeSO 4 , Na 2 S, Na 2 SO 4 , Na 2 CO 3 , etc., the presence 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.
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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 can be discarded by using a spiral concentrator with large processing capacity, low investment and low cost, and most of the gangue can be discarded.
Residual agent for slime. Then flotation separation is carried out. Technically more reliable and economically more reasonable.
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3 lead and copper cyanide tailing sulfur Comprehensive Recovery 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 The drug is 1200g/t, and the No. 2 oil is 200g/t. Ph=10.
The flow chart of the copper-lead-sulfur flotation process for the comprehensive recovery of cyanide tailings from the plant is shown in Figure 1. The results of the production process are shown in Table 2.
Figure 1 Flow chart of copper-lead-sulfur recovery flotation of cyanide tailings
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Table 2 Results of flotation recovery of cyanide tailings
Flotation concentration (%) | Product name | Yield(%) | Grade (%) | Recovery rate(%) |
Au(g/t) | Ag(g/t) | Pb | Cu | Au | Ag | Pb | Cu |
55 | Lead concentrate | 39.86 | 9.66 | 1100.00 | 46.72 | 4.10 | 77.00 | 81.88 | 93.34 | 38.72 |
33 | Copper concentrate | 13.75 | 3.26 | 410.00 | 6.00 | 16.50 | 9.00 | 15.86 | 4.16 | 53.92 |
Sulfur concentrate | 46.39 | 1.50 | 30.00 | 1.07 | 0.66 | 14.00 | 2.26 | 2.50 | 7.36 |
Cyanide tailings | 100.0 | 5.00 | 508.76 | 19.95 | 4.21 | 100.00 | 100.00 | 100.00 | 100.00 |
 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.
references
1 Jilin Province Metallurgical Research Institute, etc. Gold's mineral processing. Metallurgical Industry Press, 1988.
2 See Bai Xibian. Flotation Pharmacy. Metallurgical Industry Press, 1985.
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