湿式素材プロセッシング

[2P0105-05-01] Application of "Organic Aqua Regia" to gold refining as the replacement for the amalgamation

○ABDUL - JALIL¹, Akihiro Yoshimura¹, Yasunari Matsuno¹ (1. Chiba university)

Keywords:ASGM, gold dissolution, dimethyl sulfoxide, copper dichloride, precipitation

In present, about 1/4 of world gold supply is produced by the artisanal small-scale gold mining (ASGM) process. This process consumes large amounts of mercury for the amalgamation of gold, and release mercury to soil, air and water. This release causes environmental pollution and health hazard. To avoid these problems and risks, in this experiment we applied the "Organic Aqua Regia" (OAR) to the gold refining as the replacement for amalgamation. This OAR consists of DMSO containing CuBr₂ or CuCl₂ and can dissolve gold at high-speed. The dissolved gold can be recovered as pure gold particle by the addition of acidic water for the gold containing OAR, and the authors confirmed the recovery of gold from E-waste. In this experiment, the authors applied the OAR containing CuCl₂ and NaCl for the model ore and confirmed the gold dissolution and recovery of dissolved gold. The model ore was made of gold wire and sand, and the concentration of gold varied from 500 ppm to 1 %. Dissolved gold was precipitated by the addition of HCl. As the result, the gold dissolution from 500 ppm model ore by the OAR treatment and the precipitation of dissolved gold by the addition of HCl were confirmed. The dissolution rates were decreased by the decrease of the concentration of gold in the ore. In contrast, the recovery ratios were about 80% in all conditions and impurities like potassium or silicon from the sand were not detected from recovered gold. Through this experiment, the authors confirmed the availability of OAR process as the refining of gold from model ore.