Progress of Novel Technologies for Metals Recovery from Metals-Containing Solid Wastes

摘要

A large number of metals-containing solid wastes were discharged from industry in China. For instance, in the nonferrous metals industry, the total production amounts reached up to 447 million tons annually. Nowadays, dump is the main disposal method for these solids wastes, which not only brings severe threats to the environment, but also causes a substantial resource waste. The present metal extraction technologies can not obtained the high-added value and the complete utilization of heavy-metal containing solid wastes because of low recycling efficiency, technical economy problem and secondary pollution. Therefore, there is no common technology of resource utilization developed yet. Based on the principles of 1) recovery of valuable metals; 2)preparation of cementitious materials from the residues; 3) recycle, reuse and reduce of solid wastes, two novel technologies, including chromium recovery selectively from chromium-containing slag by bioleaching and immobilization of heavy-metal containing waste residue using elemental sulfur, have been put forward, investigated, and great progress has been made. For chromium-containing slag, it was bioleached using Ch-1 inoculum isolated from the sewage near the slag-dumped site. Cr(VI) in leachate can not be detected when chromium-containing slag has been column-leached for 7 days, and Cr(OH)3 content in precipitate is up to 32.8% with great value of resource recycling. The content of Cr(VI) in chromium-containing slag detoxified meets the National Identification Standard for extraction procedure toxicity for hazardous wastes(GB5085-1996) in China, moreover approximately 90% of Cr(VI) existing in chromium-containing slag has been recovered. For heavy metals-containing residues, it was sulfurated and converted into metal sulfide or artificial metal sulfide minerals that could be recycled through flotation separation. The heavy metals Cd and Zn could be immobilized effectively by elemental sulfur. The Cd concentration of the solidified sludge with 55% of sulfur addition was lower than the identification standard. The process of sulfur immobilization could be achieved in a very short heating and agitating time, with the optimal temperature of 140°C. These common technologies can be widely applied to dispose the solid wastes containing metals, and comprehensive recovery of valuable metals and reasonable utilization of residues can be accomplished successfully.