Leaching of Metals from Dental Silver Alloy Wastes

Environmental issues of hazardous metal wastes as well as growing demand for metals has increased focus on the forthcoming provision of metals. Therefore, the recovery and recycling processes of precious metals from secondary resources have become more prominent in the last years. Silver is one of the precious metals which can be recovered from wastes such as electronic wastes, coin and medal production losses, photographic films, and dental filling materials known as amalgam, which has the highest silver content. The present paper investigates the acid leaching of metals from a waste sample of dental silver alloy generated during the melt spray process. The alloy constitutes of ۴۲.۱۳% Ag, ۳۱.۰۳% Sn, and ۲۶.۸۴ Cu. The phase composition of amalgam generally consists of Ag۲Hg۳, Ag۳Sn, SnxHg, Cu۶Sn۵, and Cu۳Sn. The effects of the system temperature (۲۵-۸۰°C), nitric acid concentration as the leachate (۱۳.۷۵-۶۵%), pulp density (۳۳-۲۰۰ g/l), and reaction time (۰-۲۴۰ min) on the dissolution recovery of silver, copper, and tin have been investigated. In the best case, we recovered ۱۰۰% of silver and ۹۸% of copper as soluble nitrates while tin was isolated as solid stannic oxide.

کلیدواژه ها:

Amalgam ، Dental alloy ، leaching ، Recycling ، Silver