Study on Solvent Extraction of Phosphoric Acid from Phosphate Ores-HCI Digestion Liquor Using Pure and Mixed Solvent

Abstract

Pure and mixed solvents are used to extract phosphoric acid from the dissolution of phosphate ores in HCl medium. Water is used to strip phosphoric acid from the organic layer. The optimum conditions for both extraction and stripping are assigned. The results indicate that the efficiency of both process depend on the nature and composition of the phosphate ore, the nature of solvents, time of contact, the ratio between organic to liquor layers and the number of the applied stages. Also the results indicate that the efficiency of the used solvents have the following order. tert-amyl alcohol > tributyl phosphate > butanol > pentanol > heptanol > octanol > methyl-isobutyl ketone.

The decrease in the efficiency of extraction with hydrocarbon chain length for alcohols is attributed to the decrease of the active units per unit volume of the alcohol, the association of the alcohol molecules which increases as the hydrocarbon chain increase and electron donor effects of the hydrocarbon chain. By using mixed solvents to extract phosphoric acid, it is found that the mixed solvents improve the separation efficiency and eliminate the emulsion formation during the shaking process of different phases.