金银分析实验室银废液中银的回收方法探讨

Discussion recovery method of silver from silver-containing waste solution in gold-silver analysis laboratory

金银实验室实验后产生大量的废银夜。采用氯化钠沉淀废液中的银,得到的氯化银沉淀渣同还原剂铁粉、熔融剂碳酸钠、助熔剂玻璃粉及硼砂按一定比例进行配料,经马弗炉高温熔炼,获得银锭,从而建立一种从废液中回收银的方法。分别以铁粉、淀粉、面粉和碳粉为还原剂进行了比对试验,结果表明铁粉还原效果最佳。还对还原剂、熔融剂、助熔剂用量及熔融时间进行了探讨,结果表明,取30g氯化银沉淀渣,加入60g碳酸钠、15g铁粉、10g硼砂及60g玻璃粉,在马弗炉中1 100℃熔炼20min,可较好的回收银锭。按照实验方法得到的银锭,银的回收率可达99.73%,银锭的纯度为99.35%。

A lot of silver-containing waste solution was produced during experiments in gold-silver analysis laboratory.The silver in waste solution was precipitated using sodium chloride.The obtained silver chloride precipitate residue was mixed with reducing reagent（iron powder）,fusion reagent（sodium carbonate）,flux（glass powder）and sodium borate according to a certain proportion.The silver ingot was obtained after high temperature melting in muffle furnace.The recovery method of silver from waste solution was established.Various reducing reagents including iron powder,starch,wheat flour and carbon powder were compared.The results indicated that the reducing effect of iron powder was best.The dosage of reducing reagent,fusion reagent and flux as well as melting time was also discussed.It was found that the recovery of silver ingot was good under following conditions：60g of sodium carbonate,15 g of iron powder,10 g of sodium borate and 60 g of glass powder were added into 30 g of silver chloride precipitate slag;then,it was melted in muffle furnace at 1 100℃for 20 min.The silver ingot could be obtained according to the experimental method.The recovery of silver could be up to 99.73%and the purity of silver ingot was 99.35%.