实验室废旧贵金属材料中铂的回收利用

实验室使用的含铂耗材会因为长时间使用形成损耗、变性或功能失效,长期搁置或丢弃造成极大的浪费,工业上常使用硼氢化钠作还原剂还原回收铂。实验依据硼氢化钾相比硼氢化钠具有分解温度高、稳定性好、在使用过程中较安全的特性,与氯化铵相结合利用二次沉淀法,以实验室含铂废旧耗材为原料,建立了硼氢化钾还原-氯化铵沉淀法回收铂的方法。为了获得纯净的金属铂,实验采用硝酸分离杂质元素,王水溶解铂,反复用盐酸驱赶氮氧化物,使铂充分转化为氯铂酸。在40℃、5%(V/V)盐酸介质中用硼氢化钾还原氯铂酸及少量难溶于王水的氧化铂,再用王水溶解铂黑并完全转化为氯铂酸,氯铂酸与过量的氯化铵形成黄色氯铂酸铵沉淀,陈化过夜。选择分段缓慢升温分解氯铂酸铵,在750℃和900℃煅烧,分别获得松散的金属铂粉和较致密的金属铂。两次沉淀溶液中残余的铂离子均小于20μg/mL。回收铂的纯度不小于99.9%,回收率大于99.5%。

Recycling of platinum from waste precious metal materials in laboratories

The platinum-containing consumables used in the laboratory may cause loss, denaturation or functional failure in long-term use. The shelving or discarding might cause great waste. Therefore, platinum was usually recycled in industry using sodium borohydride as the reducing agent. Compared to sodium borohydride, potassium borohydride had some advantages such as high decomposition temperature, good stability and safety performance in the use. Combined with the secondary precipitation method of ammonium chloride, a method for recovering platinum from the waste platinum-containing consumables in the laboratory was established by potassium borohydride reduction-ammonium chloride precipitation in experiments. In order to obtain pure metallic platinum, the impurity elements were separated by nitric acid. Then platinum was dissolved with aqua regia. The nitrogen oxides were removed repeatedly using hydrochloric acid, so that platinum was fully converted into chloroplatinic acid. In 5% (V/V) hydrochloric acid medium at 40℃, potassium borohydride was used to reduce the chloroplatinic acid and little platinic oxide which was hardly dissolved in aqua regia. The platinum black was dissolved in aqua regia and completely converted to chloroplatinic acid, which was then converted to the yellow ammonium chloroplatinate precipitate by reaction with excess ammonium chloride. After aging overnight, the ammonium chloroplatinate was decomposed by slowly increasing the temperature. After calcination at 750℃ and 900℃, the loose metallic platinum powder and denser metallic platinum were obtained, respectively. The contents of residual platinum ions in secondary precipitation solutions were all less than 20μg/mL. The purity of the recovered platinum was not less than 99.9%. The recoveries were greater than 99.5%.