Recycling Technology of Precious Metals.

The separation and purification methods of precious metals from the scrap containing precious metals are introduced in this review. The solid waste containing precious metals first is dissolved by the solution comprising oxidation agents and ligands, such as aqua regia, Cl2 + HCl and NaCN + O2. The separation of precious metals in the leached solution or wasted solution is carried out by using various methods like classic precipitation, cementation, ion exchange resin, activated carbon adsorption and solvent extraction. It depends on the concentration and combination of precious metals what kind of separation method is applied. Generally, adsorption and ion exchange methods are applicable to the dilute solution, while precipitation, cementation and solvent extraction are used for the concentrated solution. In the recovery of the precious metals in automobile catalyst, the collection of the platinum group metals in Cu or Fe metal melted by a plasma melting method is performed as one of the recovery techniques by the pyro-metallurgy.The fundamental of separation and purification methods, and some commercial plant examples are described for recycling of precious metals.