The phosphine oxides Cyanex 921 and Cyanex 923 as carriers for facilitated transport of chromium (VI)-chloride aqueous solutions

摘要

The behaviour of the phosphine oxides Cyanex 921 and Cyanex 923 in the facilitated transport of chromium (VI)\udfrom chloride solutions is described. Transport is studied as a function of several variables such as stirring speeds of the\udaqueous phases, membrane phase diluent, hydrochloric acid concentration in the source phase and chromium and carrier\udconcentrations. The separation of chromium (VI) from other metals presented in the source phase as well as the\udbehaviour of phosphine oxides with respect to other neutral organophosphorous derivatives (tri-n-butylphosphate\ud(TBP) and dibutyl butylphosphonate (DBBP)) are also investigated. Moreover, by using hydrazine sulphate in the\udreceiving phase, Cr(VI) is immediately reduced to the less toxic Cr(III).