THE CHEMISTRY OF GOLD SOLVENT-EXTRACTION FROM ALKALINE CYANIDE SOLUTION BY SOLVATING EXTRACTANTS

The chemistry of gold extraction from alkaline cyanide solution by solvating extractants, particularly TBP and DBBP, is described. Undiluted TBP is an effective extractant for gold at high ionic strengths, whereas undiluted DBBP needs little ionic strength adjustment in order to extract gold. Other alkyl phosphorus esters, phosphine oxides, sulfoxides, and sulfones also act as solvation extractants. The solvation extraction of gold is thought to occur by ion pair solvation according to the following reaction: M+ + Au(CN)2- reversible-M+ ...Au(CN)2-BAR. Infrared spectroscopic analysis indicates that there is no specific coordination of the TBP or DBBP to the gold center in the Au(CN)2- complex. The significance of the solvation extraction phenomenon in the extraction of gold by modified amines is discussed, and analogies with the adsorption of gold onto activated carbon are drawn.