Points With Silver Dross Recycling Process Research

Silver separating residue is the remaining residue after which the copper anodic mud had been extracted the precious metals: gold, silver, platinum and palladium, as well as value elements: copper, selenium and tellurium. This paper presented the extraction method & research state of precious metals and mainly studied the comprehensive recovery and utilization of precious metals and value elements from silver separating residue, which develops the methodology of recovering second-hand non-ferrous resource & protecting environment, and which is much practical significance. It suggested that the technologic process of comprehensive recovery precious metal from silver separating residue firstly leach out gold by leach reagent chlorate, following silver by ammoniacal thiosulfate containing copper, which the leach rate of gold, silver.platinum and palladium could been reached by above 98%,95%,85%,85% respectively. As follows is the optimum parameter of process.The experiments had been investigated the factors such as concentration of leach reagent, acidity, reaction time, solid & liquid scale and temperature that influenced the leach ratio, compared with the leach effect between the leach reagent amine acetate and NaCI-HCI. The result indicated that leach effect was much better under the lixivium of NaCI-HCI, and concluded to the optimum technologic condition: solid & liquid scale 1: 8~10, hydrochloric acid 75g/l, sodium chloride 250g/l, temperature 95 C, reaction time 1 hour,which the lead leach rate could obtain above 95%,antimony above 75%.After residue containing high silver had been pre-roasted under temperature 500 C,the leaching rate could gain 95% through leach reagent sodium sulfite, and investigated a few factors that influenced the leach reaction, concentration of sodium sulfite, acidity, solid & liquid scale, temperature and reaction time. The optimum technologic parameter had been reached: S:L=1:8~10, Concentration of sodium sulfite, about 200~260g/l, reaction time 1~3hour,temperature 30~40 C,pH=8~10.Through analyzing the chemistry & thermodynamics of ammoniacal thiosulfate containing copper leaching gold and silver, silver separating residue containing low silver leaching out gold and silver can obtain good effect under it, investigating the factors, concentration of thiosulfate, sodium sulfite, copper, ammonia, solid &liquid scale and reaction time. The optimum parameters had been reached: S:L=1: 6, temperature 35~45 C, ammonia 6~12g/l,sulfite 10~ 20g/l, copper sulfate 2~4g/l, sodium thiosulfate 30~50g/l, reaction time 2h~3h.An investigation of influencing factors, sodium chlorate, sodium chloride,vitriol, temperature, solid & liquid scale and reaction time, had been carried out through chlorate leaching precious metal, gold, platinum palladium, and optimum parameter had been reached: S: L=1:6-10,sodium chlorate 25~30g/l, NaCI 10~20g/l, H2SO4 9~18g/l, reaction time 2h, temperature 95 C.Under the temperature 60 C, the study had carried out the calculation of kinetics parameters from result of ammoniacal thiosulfate containing copper leaching gold and silver: leaching gold, apparent activation energy(AAE) E=1.87kJ mol-1,frequence factor k0=4.48 10-5dm3 mol-1 s-1; leaching silver, E=0.507kJ-mor1, k0=3.33 10-4 dm3 mol-1 s-1.The paper had suggested the experiment of deoxidizing the gold and silver from lixivium of thiosulate by reducing reagent hyposulphite, which the results showed that deoxidizing rate was reached by Au 99% and Ag 95% or so.