沉淀法回收废定影液中的银

以过氧化氢、磷酸、硫酸、盐酸、甲酸、乙酸为沉淀剂,将废定影液中的银以硫化银的形式沉淀出来,经熔炼后得到金属银。试验考察了沉淀剂的种类、30%过氧化氢用量、陈化时间、加料顺序对银回收率的影响,其结果表明,滴加30%过氧化氢至淀粉-碘化钾试纸变蓝、陈化24 h条件下回收废定影液中银的效果最好,银回收率达98%以上。过氧化氢沉淀回收废定影液中的银,无有害气体产生,不产生二次污染,是对环境友好的绿色沉淀剂。

Study on recycling silver from waste fixative through precipitation

Silver sulfidewas precipitatedin the waste fixative with hydrogen peroxide,phosphoric acid, hydrochloric acid, formic acid, acetic acid used as precipitants, and then metallic silver wasextracted by melting the precipitated silver sulfide. The effects that the parameters including different kinds of precipitants, the amount of 30 % hydrogen peroxide dosage, aging time and feeding sequence have on the silver recycling rate were studied. The results indicated that the recycling effect of silver from the waste fixative was the best （the recycling rate were more than 98 % ） when the dosage of 30 % hydrogen peroxide makes the starch-potash iodide test paper blue and the aging time is 24 h. In addition, there were no poisonous gas byproducts and no secondary contamination when usinggreen environment-friendly hydrogen peroxide as precipitant.