Biochemical decomposition and gold leaching of refractory ultrafine grinding sulfur concentrate

To calcine and firing the basis of cyanide, sulfur concentrate containing gold fine processing technology for analysis. The process can achieve higher indicators in the case of low investment and operating costs, but this is closely related to air pollution caused by toxic compounds of arsenic and sulfur, so further improve some gold extraction from gold-containing sulfur concentrates. Desirable hydrometallurgy and the development of new processes that meet modern environmental requirements are a pressing task.
From the standpoint of developing a roasting-free process, it is important to combine the mechanochemical activation of the ultrafine grinding of the concentrate with the next step of treating the microbial biomass with its alkali hydrolysate to decompose and leach gold.
Gold biochemical decomposition and leaching processes were studied for flotation concentrates containing 30 g/t Au, 8.1% As, 24.3% S and 25.4% Fe. Based on reasonable analysis of the information, nearly 6% of Au in sulphide -? Pyrite and arsenopyrite as disseminated gold. Gold is finely divided in these two minerals, most of which are gold particles with a particle size of no more than 1 micron. Difficult to treat concentrates do not include their direct cyanidation, as direct cyanidation can extract nearly 8 to 10% Au. Even after ultrafine grinding, the extraction rate of gold in cyanide solution does not exceed 23~28%. It is only when the sulfide mineral is decomposed that it is possible to decompose the gold of the pigment, so the hydrometallurgical method is most reasonable.
The alkali decomposition index of the gold-containing sulfide was compared with the index of gold leaching from the concentrate (the arsenic in the planetary gear grinding reaction in the air medium). A periodic speed planetary gear mill was used in the test. The ball loading is 35 to 40 times larger than the amount of ground material, and the acceleration is equivalent to 40 to 50 grams. The concentrate is ground by a 3C-06 type grinding machine, and compressed air (P = 4.5 to 4.7 atmospheres) is used as a power medium. When the jet was ground, the resulting product had a particle size of 85% of 4 microns and a specific surface area of ​​4.8 m 2 /g. The original concentrate has an 80% particle size of 0.074 mm (no more than 1% of the 4 micron size).

As shown in Fig. 1, whether it is the planetary gear grinding or the jet grinding treatment concentrate, the comparison results of the alkali decomposition of the sulfide mineral (sulfur contained in the solution) can be obtained.
However, when gold is extracted from the activated product, a significant difference can be observed. Even when a cyanidation solution is used, there will be 16 grams per ton of gold-containing tailings on the concentrate of the planetary gears (after alkali treatment) (Fig. 2). In this case, when processing the original concentrate and activation (20 points and more time) concentrate, the consumption of NaCN is increased from 0.2 to 8 kg/ton, which is to improve the reactivity of the mineral components. condition. Only in the jet mill, according to the alkali treatment-cyanide process, the highest recovery rate of 65-70% of the gold in the activated concentrate can be achieved. At this time, the remaining content of the tailings gold is one-half less than that of the planetary grinding. . The difficulty of gold cyanidation increases as the leached product of the planet is leached, presumably because of the surface passivation of the gold particles. The authors of this reference were observed. The next test is more focused on jet milling.
An actual possibility has been proposed earlier: the use of an alkaline hydrolyzate of yeast biomass, and a mixed solution of a hydrolysate and sodium cyanide to decompose and leach gold from the activated concentrate. The following ingredients were obtained by treating the industry to produce feed yeast in a caustic soda solution. The product is decomposed; the total amount of amino acids is 5 g/L, the nucleic acid is 0.5-0.8 g/L, the lipid compound is 1-2 g/L and the NaOH is 20-30 g/L. The liquid: solid minimum ratio that guarantees the highest indicator of withdrawal gold must be determined. Liquid: solid = 8:1 and more is the ideal ratio of hydrolyzed product (amino acid 2 g / liter) and sodium cyanide (0.15%) mixed solution, at this time, the solution gold recovery rate is ~ 70% (Figure 3 ). However, under such dilution conditions, only 40% of Au was transferred to the hydrolyzate solution without addition of cyanide. The extraction rate of gold is actually directly dependent on the ratio of liquid to solid. When the slurry is diluted to liquid: solid = 16:1, the extraction rate can also reach 70%.
Gold was leached with the observation solution mainly during the first 48 hours of treatment (Fig. 4). 62% Au can be extracted by leaching the activated concentrate with the hydrolyzate for 96 hours, while 76% can be extracted with the same solution with cyanide added. In the case of an oxidizing agent without sodium cyanide, the efficiency of the hydrolyzate solution is significantly improved, and nearly 76% of Au can be extracted. [next]

Gold was extracted from the hydrolyzed product solution using AM-2B resin. When the equilibrium concentration of the metal in the solution is 1.4 mg/liter, the saturated resin capacity of gold is 40 mg/g. At the next gold extraction, the recycled resin does not lose its adsorption properties.
According to the test results, it can be considered that the adsorption leaching test for improving the conditions for extracting gold and extracting the index has achieved the intended purpose. In the adsorption leaching test, the amount of the resin AM-2B added was 5% by weight of the solid product. It has been found that when liquid: solid = 6:1 (see table), most of the gold is extracted within 48 to 50 hours. Under these conditions, 76.8% of Au is adsorbed on the resin, which is the index compared to the average filtration process. When the liquid: solid = 10:1, the hydrolysate and sodium cyanide or hydrolyzate are used. The mixed solution with the oxidizing agent is leached, and when the liquid = solid 16:1, it is leached with the hydrolyzed product solution).

Slurry density (liquid: solid)
Gold content in the gold removal solution, mg/L
Gold content in leaching slag, g / ton
Resin adsorption rate of gold, %

When the liquid: solid = (8-10): 1, the adsorption leaching time is increased to 72 hours, the gold extraction rate can be increased to 83.4% and the tailings with a gold residual content of 5 g/ton can be obtained. The jet pulverized concentrate is adsorbed and leached at different pulp densities. Adsorption leaching time - 48 hours, resin addition amount - 5%.
It has been confirmed that recycling of the hydrolyzate solution is possible in principle. After the second and third cycles of the solution, gold is leached from the newly added concentrate, at which time the solvent's reactivity is reduced by one-third and one-half, respectively. If the solution is re-concentrated with a new solvent, a higher process specification can be achieved.
Reasonable analysis of the adsorption leaching residue shows that the decomposition of gold associated with sulfide is very high and is mainly decomposed by chemical methods; the gold content is reduced from 25.8 g/ton in the original concentrate to 15.2 g in the jet milled product/ Ton and leached tailings of 2.8 g / ton.
The distribution of arsenic in each stage of the treatment was also studied. When the concentrate is treated with an alkali hydrolyzate, the arsenopyrite is decomposed and 70 to 75% of the arsenic is transferred to the solution. The arsenic content in the solution does not actually change before and after adsorption, that is, arsenic does not adsorb to the resin. The gold removal solution can be used to remove arsenic by known methods prior to throwing away.
In view of the results of the completed comprehensive study, it is recommended to adopt a principled process flow (Figure 5). Large-scale trials for the treatment of difficult gold-arsenic concentrates. According to this procedure, the concentrate is ground by a jet mill and adsorbed and leached with an alkaline solution of the protein hydrolysate. [next]

In addition to favorable concentrate activation conditions, the use of jet mills has the following advantages: This equipment has been mastered by the industry and has high productivity (up to 100 tons/hour), simple structure, low metal consumption and low price. The solvent can be obtained from industrially released yeast biomass (containing 50% protein) by alkaline hydrolysis and subsequent dilution. In order to understand the gold absorption and regenerating adsorbent, the gold-containing resin was reprocessed according to the standard procedure, and the commercial gold was analyzed by the thiourea eluent. In view of the necessity of precipitating and preserving arsenic-containing deposits and the rationality of the return of the gold-removing solution, the adsorbed leaching slurry is dewatered by a centrifuge. The solution precipitates arsenic by lime, after which most of the solution is diluted by the original hydrolysate.
The expanded technical and economic evaluation of the process, including the cost of obtaining concentrate, the cost of 1 gram of gold is within the allowable cost limit.
Conclusion 1. If the planetary system of the concentrate is compared with the jet regime, the latter is preferred because the residual gold content of the jet leaching tailings is less than half that of other planets under the same treatment conditions.
2. The protein hydrolysate is effective when the activated concentrate is adsorbed and leached. When the liquid: solid = (6 ~ 8): 1 and treatment time 48 ~ 50 hours, resin gold extraction 80%, leaching time increased to 72 hours, the extraction rate of gold in the hydrolysis solution can be increased to 83.4%. Arsenic is enriched in the gold removal solution and can be precipitated by known methods for storage.
3. It is recommended to use a large-scale experiment to treat refractory sulfide concentrate processes based on jet milling and adsorption leaching with protein hydrolysate.

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