摘要
热力学分析表明,从氯盐浸出液中用铅置换银较为有利。试验了置换时间、温度和料液 PH 对银置换率的影响,获得了最宜的置换条件:2～3小时,70～75℃和 PH0.8～1.5。在最宜条件下,在小试和扩大试验中,银的置换率均大于98%,从银泥到制取金属银锭,试验了四种工艺路线,经综合比较,确定以 H_2SO_4-NaCl-NaClO_3转化路线为最佳。银转化成氯化银留于固相,接着进行液固分离;加氨水于固相,溶解氯化银;然后用水合肼处理溶液以还原银;并过滤、干燥沉淀,用碳酸钠和硼砂作熔剂,于1050～1100℃熔炼,得到纯度大于99%的银锭,银的总回收率大于95%。
It is favourable to cement silver with lead from chloride leaching solut- ions,based on thermodynamic analysis.The experiments for the effect of cementation time,temperature,arid PH of feed solutions on the yield of cementation silver are carried out,and the optimum cementation conditions are obtained,viz.2～3 hours,70～75℃,and PH 0.8～1.5.The yield of silver cemented is more than 98% under the optimum conditions both in the small tests and in the enlarged tests.Four processes for preparing silver ingot from silver sludges are examined,and the H_2SO_4-NaCl-NaClO_3 conv- ersion process is confirmed to be the best of them through comprehensive comparisons.Silver is converted into silver chloride leaving in solid phase, followed by separating liquid from solid,aqueous ammonia is added to the solid to dissolve silver chloride,and then the solutions are treated with hydrazine hydrate in order to reduce silver,filtering and drying the precip- itate;finally melted at 1050～1100℃ using sodium carbonate and borax as fluxes,obtaining an ingot of silver of greater than 99% purity in a total recovery of more than 95%.
关键词
铅
置换法
回收
银
氯盐
浸出液
silver
lead cementatiou
recovery
chloride leaching solution
reduction
hydrazine hydrate
silver ingot
