Extraction of Metal Salts by Mixtures of Water-Immiscible Amines and Organic Acids (Acid-Base Couple Extractants). 1. A Review of Distribution and Spectroscopic Data and of Proposed Extraction Mechanisms

Distribution data and extraction mechanisms are reviewed for metal salt extraction by mixtures of water immiscible amines and organic acids in a diluent. Some new results from our laboratory were included to widen the scope of extractant components, provide more data on extraction of transition metal sulfates from concentrated solutions, and study the mutual effects of extraction and aqueous-phase acidity. An effort was made to present a matrix of the affecting parameters (extracted salt and extractant characteristics, aqueous-phase concentration and acidity, organic-phase concentration, temperature, etc.) and the distribution data (capacity and extraction selectivity and stoichiometry, the shape of the distribution curve, and water coextraction). This data provides the tools required for tailoring extractants for many hydrometallurgical and waste management processes. In addition, it provides the basis for analysis of the mechanisms involved and of the species present in the organic phase.