Chlorination Methods Applied to Recover Valuable Metals from Roasting-cyaniding Residue.

Residue from refractory gold ore contains considerable gold after roastingcyaniding process because of high content of arsenic. Most gold in the residue is encapsulated by other minerals and hard to be recovered. In the present paper, chlorination methods were adopted to extract gold, copper, zinc and lead. The residue is first mixed with CaCl₂ solution, and then pelletized, dried and heated in a tube furnace. The effects of heating temperature, heating up time, CaCl₂ addition and holding time on volatilization ratio of gold, copper, lead, and zinc were investigated. Volatilization start temperatures of chlorine and metal elements were confirmed. The main reactions in the process were confirmed, which occurred between CaCl₂ and the residue to form Cl₂/HCl and various calcium salt. Reactions between CaCl₂ and sulfide, silica, arsenide and iron oxide break the wrap of gold. Higher heating temperature and more CaCl₂ addition had positive effects for chlorination. However, longer heating up time was bad for chlorination because of the volatilization of chloride during the heating up. More CaCl₂ addition could make up the influence of longer heating up time. Research results in the paper will contribute significantly to the design of reaction equipments. [ABSTRACT FROM AUTHOR]