| Cyanide tailings is the solid waste of a variety of valuable metal generated in the gold extraction process by cyanidation. China, as the largest producer of gold, produces more than 20 million tons of cyanide tailings annually, which the iron grade of even is larger than the number of poor iron ore. It is of great significance to make theoretical research on cyanide tailings for comprehensive utilization of valuable metals in it,when facing the grim exhaustion of the mine resource.In this paper, the cyanide tailings is from a gold smelting enterprises in Henan. Through SEM, XRD, chemical analysis and other means of characterization, the raw materials were analyzed in detail over the composition and phase identification.. This paper expounds the dissolution mechanism of iron oxide and silicon oxide in cyanide tailings inn acid and alkali respectively. It used sulfuric acid leached cyanidation slag to extract the iron. The experiment investigates the effect of reaction temperature, reaction time, sulfuric acid concentration and liquid to solid ratio on leaching rate of iron, determining the optimum process conditions is the liquid to solid ratio,6:1, sulfuric acid concentration,480g/L;leaching time, 5h,leaching temperature,160℃. Under the optimized conditions, the grade of gold in acid leaching residue was 2.87g/t. The cyanide leaching experiments determine the optimum conditions: leaching time, 48h; the mass fraction of sodium cyanide, 0.7%; liquid to solid ratio, 4:1. Under conditions above, gold recovery rate for 100 gram acid leaching residue is 79.91%. which improves 67.41% compared with the direct cyanidation.In this paper, alkali leaching method by NaOH and molten salt roasting method were used in the treatment of cyanide tailings to study the change of iron phase after removal of silicon phase, and the effect of change of iron phase on the recovery rate of gold was studied further. Experiment of alkaline leaching cyanide tailings by sodium hydroxide determines the optimal conditions are as follows: reaction temperature, 95℃; leaching time, 4h; liquid solid ratio,15:1; alkali concentration 50%; stirring speed, 300r/min. Grade of gold in alkali leaching tailings is 3.14g/t, which is significantly improved than the original tailings. Grade of Gold in alkali leaching slag leached by conventional cyanidation increased by 69.49% compared with the original cyanide tailings. The effect is remarkable. Mixing molten salts were used to roast cyanide tailings. Optimum conditions for the experiment were determined: roasting time, 2h; NaOH and NaNO3 quality ratio,1:1;roasting temperature, 500℃. Morphologies of tailings was observed under optimal conditions. It was found that iron and silicon phase dip even more significantly, which is obviously many column forms in the tailings. From SEM scanning results it shows that silicon is obvious to more concentrated than iron phase, and the gold concentrated area is same with silicon, indicating that using molten salt to treat cyanide tailings makes the raw material structure become loose and porous, which may make the gold in Fe phase transferred to Si phase, and then water leaching makes this part of the silicon soluble in aqueous solution to make the gold encapsulated in silicon exposed in the subsequent cyanidation process. the grade of gold in the cyanide tailings is 2.46g/t. The recovery rate of gold from cyanide increased by 45.1% compared with direct cyanide, and the effect is significant. |
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