Extraction of As (V) from sulphuric acid solutions by Cyanex 925

Abstract

The extraction of As (V) from sulphuric acid solutions using the phosphine oxide Cyanex 925 dissolved in various diluents was studied. Arsenic extraction depends strongly of temperature, decreasing with the increase of this variable, and to a lesser extent on the sulphuric acid concentration, approximately up to 300 g/L H₂SO₄. To increase the degree of arsenic extraction it needs to operate with Cyanex 925 concentrations of at least 50 % v/v, although this also promotes the coextraction of the acid. Stripping of the loaded arsenic and sulphuric acid can be carried out using water, better As-H₂SO₄ separations can be obtained at lower temperatures or operating using high O/A ratios for acid stripping and lower O/A ratios for arsenic stripping.