lixiviant

A lixiviant is a liquid medium used in hydrometallurgy to dissolve valuable metals from ore or waste rock. The lixiviant reacts with the mineral matrix to convert solid metal minerals into soluble metal species, producing a metal-bearing solution from which the metal can be recovered later.

Common lixiviants include cyanide solutions for gold and silver; sulfuric acid-based systems for copper and some uranium ores; chloride-based solutions such as ferric chloride or hydrochloric acid for certain base metals; and ammonium or carbonate systems for specialty ores. In addition, thiosulfate and organic acids are used in non-cyanide or low-toxicity alternatives, while bioleaching employs microbial activity to generate organic or inorganic lixiviants in situ.

Applications include heap leaching, vat leaching, agitation leaching, and in-situ leaching, where ore is wetted with the lixiviant and kept in contact for a period to maximize dissolution. The resulting metal-laden solution is processed by precipitation, solvent extraction, ion exchange, or electrowinning to recover the metal.

Considerations encompass ore mineralogy, metal grade, leach kinetics, and environmental and regulatory factors. Cyanide-based leaching enables high gold recoveries but requires stringent safety and tailings management due to toxicity. Acidic and chloride leaches can be more aggressive, potentially generating acidic effluent or corroding infrastructure, necessitating careful management and treatment. Emerging non-toxic or low-toxicity lixiviants aim to reduce environmental impact.

See also: hydrometallurgy, heap leaching, in-situ leaching, solvent extraction, electrowinning.