Extraction Separation Studies of Gold by 2-Hexylpyridine

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Abstract
The high molecular weight pyridine amine, 2-hexylpyridine, has been studied as a component of solvent extraction systems. Extraction of mineral acids by the compound is described. The ionization constant (pKBH +) has been determined by potentiometric titration and spectrophotometrically. The distribution of Au(III) between solutions of 2-hexylpyridine in benzene and different mineral acid solutions has been investigated as a function of the concentration of the acids, extractant, and salting-out agents. The extraction mechanism and the composition of extracted complexes of Au(III) are discussed. Separation factors of a number of metal ions relative to gold have been reported, and the determination of gold from a number of synthetic and ore samples was made by neutron activation analysis. 2-Hexylpyridine has been shown as a selective extraction reagent for gold. It has been shown that 2-hexylpyridine dissolved in benzene will extract gold efficiently and reversibly from moderate acid chloride, nitrate, and sulfate media, and that among the common anions only neutral chloride exerts a slight depressing effect on extraction when present in high concentration. The presence of ferric iron does not interfere with extraction.