Gold Extraction and Recovery Processes

Various methods such as gravity concentration, flotation, panning, pyrometallurgy, and cyanidation are available for the extraction of gold metal from its ores, with cyanidation being the most commonly utilized method. This process involves dissolving gold-containing ores in dilute cyanide solution in the presence of lime and oxygen. For refractory ores, which do not readily undergo cyanide leaching, alternative treatments such as pressure oxidation, roasting, chloration, and biooxidation are discussed to expose gold particles for effective cyanidation. Thioura leaching, developed as a less toxic and more rapid alternative to cyanide leaching, is noted along with other potential lixiviants like bromides, chlorides, and thiosulfate. Recovery methods for gold solutions include carbon adsorption, the Merrill-Crowe process, electrowinning, and ion-exchange/solvent extraction. The report emphasizes the historical significance of gold, highlighted by traditional methods such as the Merrill-Crowe process and emerging techniques like the Carbon in Pulp (CIP) method, which enhances recovery efficiency by using granular carbon in a series of agitating tanks. Additionally, a summary of patented processes and examples of commercial gold mining and recovery practices is provided.