EXTRACTION OF ARSENIC(Ⅲ) AND ARSEniC(Ⅴ) FROM SULPHURIC ACID SOLUTIONS WITH TRIALKYLPHOSPHINE OXIDES AND HYDROXAMIC ACIDS

摘要

The extraction of As(Ⅲ) and As(Ⅴ) from sulphuric acid solutions of various concentrations (50-200 g/dm~3) with Cyanex 923, Cyanex 925 and neo-decanohydroxamic acids, was studied. These extractants were dissolved in toluene, and in Exxsol D 220/230. Cyanex 923, Cyanex 925 and neo-decanohydroxamic acids can be considered as effective arsenic extractants. Sulphuric acid is co-extracted into the organic phase. Extraction of both As(Ⅲ) and As(Ⅴ) occurs rapidly and the equilibrium is obtained after 5-15 minutes. The isotherms of As(Ⅲ) and As(Ⅴ) extraction at various sulphuric acid concentrations were determined. The diluent affects significantly the extraction of As(Ⅲ) with Cyanex 923 and Cyanex 925. Toluene is a better diluent than Exxsol D 220/230. In the case of neo-decanohydroxamic acids the effect of diluent on extraction efficiency is very small. Arsenic (Ⅴ) is always extracted better with the reagents diluted with toluene. Arsenic can be stripped with water.