The process comprises the following steps: preparation of a mixed system of sodium iodate, sodium iodide and water; production of complex salts of Au(I) and Au(I₃) under the action of the as-prepared mixed solution and a co-oxidant; extraction of crude gold powder; and purification to obtain refined gold powder.

Compared with the prior art, the gold iodide leaching method adopted in this process significantly improves the extraction recovery and purity of the recovered gold. Meanwhile, the process features simple operation, low environmental risk of the involved chemicals, and low cost, thus reducing production cost and improving production efficiency. Furthermore, iodine can be recycled and reused in the process, which further cuts production costs.

The lead-bearing gold concentrates are treated with the independently developed crystallization washing technology, which enables hydrometallurgical separation of impurities including lead, iron and sulfur during gold smelting and extraction. This process features innovative and unique design, strong adaptability, and wide applicability for refining lead-bearing concentrates (including middlings) obtained from Knelson gravity concentration. It also provides high reference value for the processing of other lead-bearing concentrates.

An increasing number of domestic gold mining enterprises in China have adopted the Knelson gravity concentration process. At present, most Knelson gravity concentrates are processed via pyrometallurgical smelting, which is associated with harsh working conditions and high risk of lead poisoning. The application of this new process can thoroughly address the lead pollution problem, thus filling the domestic gap in this technical field.

Process for Comprehensive Recovery of Precious and Rare Metals (Gold, Silver, Platinum and Palladium) from Gold-Bearing Waste

This process is implemented as follows:

Gold-bearing waste is first roasted in a rotary kiln, after which copper, bismuth and other impurities are leached out using sulfuric acid, industrial salt and sodium chlorate. Copper and bismuth in the primary leachate are recovered separately with caustic soda and soda ash.

The primary leaching residue is then leached with hydrochloric acid (or sulfuric acid) and sodium chlorate to obtain secondary leaching residue and a gold-, platinum- and palladium-bearing solution. Silver remains in the secondary leaching residue and is enriched therein.

After the pH of the gold-, platinum- and palladium-bearing solution is adjusted by adding soda ash, anhydrous sodium sulfite is dosed into the solution. Precipitation and filtration are then carried out to produce sponge gold and a platinum- and palladium-bearing solution.

Zinc powder is added to the platinum- and palladium-bearing solution, and platinum-palladium sludge and wastewater are obtained after further precipitation and filtration. Palladium powder and platinum powder are finally produced via conventional platinum and palladium extraction processes.

The present invention can address the common defects of traditional processes, including severe environmental pollution, low direct recovery rate, slow capital turnover and low labor productivity.