hydrometallurgical

Hydrometallurgy is a branch of extractive metallurgy that uses aqueous solutions to recover metals from ores, concentrates, and secondary materials. It encompasses leaching, solution purification, precipitation, solvent extraction, ion exchange, and electrowinning. Compared with pyrometallurgy, hydrometallurgy typically operates at ambient or moderate temperatures and can be more selective for certain metals.

The typical hydrometallurgical flow begins with dissolving the target metal from the ore into a leachate, using acidic, alkaline, or biological solutions. The resulting solution is then treated to remove impurities and concentrate the metal, through precipitation, solvent extraction, or ion exchange. The metal is finally recovered from the purified solution by precipitation or electro-winning, and residual streams are recycled or treated to protect the environment.

Common techniques include heap leaching, vat leaching, and in-situ leaching for oxide and low-grade ores, as well as agitated-tank leaching for sulfide ores. Solvent extraction and electrowinning are particularly important for copper. Cyanide leaching is widely used for gold recovery, while acidic or alkaline leaching followed by solvent extraction can be applied to nickel, cobalt, uranium, and other metals. Hydrometallurgy can also process secondary materials such as spent catalysts, electronic waste, and recycled metals. Bioleaching, which uses microorganisms to assist dissolution, is another notable approach.

Environmental and economic considerations include managing chemical use, tailings, and leach solutions to prevent contamination, recycling reagents, and ensuring regulatory compliance. Hydrometallurgy offers lower capital costs and suitability for low-grade or finely disseminated ores, balancing performance with stewardship of natural resources.