Recovery of silver and mercury from dental amalgam waste

Abstract

A simple, inexpensive scheme was developed to recover silver and mercury from silver-tin dental amalgam waste. Direct distillation of the amalgam under reduced pressure yielded 99.22 ± 0.68% pure mercury with 87.7 ± 3.6% recovery. It was shown that the recovered mercury could possibly be further purified to 100.03 ± 0.14% by redistillation. Silver was isolated from the residue as silver chloride, which was then converted to silver oxide and diamino-silver(I) complex for chemical reduction by glucose and electrochemical reduction, respectively. The former method recovered 92.4 ± 2.5% silver of 99.5 ± 1.1% purity; the latter yielded silver with a slightly lower recovery, 89.9 ± 3.1%, but higher purity, 99.99 ± 0.17%. Parameters governing the two recovery routes were also investigated.