On the kinetics of Cu, As and Sb transport through cation and anion exchange membranes in acidic electrolytes

Abstract

Experiments were conducted in a batch electrodialysis cell containing aqueous acidic solutions of copper, arsenic and antimony in order to evaluate their transport kinetics through commercial ion exchange membranes. A relatively high unwanted transport of bisulfate through the cation exchange membrane was observed with the transport rate being 0.39 mol/h/m2 at 225 A/m2. The bisulfate transport rate through the anion exchange membrane was found to be 1.05 mol/h/m2 at the same current density. The transport rate for the unwanted transfer of copper ions through the anion exchange membrane varied linearly with time and current density; the transport rates were 0.07 and 0.10 mol/h/m2 at 150 and 225 A/m2, respectively. These values were found to be lower than 1/7 of the transport rate of copper for both current densities, through the cation exchange membrane. Arsenic transport was found to be highly dependent on speciation. In a 1.5 mol/L H2SO4 solution, As(III) was transported as AsO+ with a rate of 0.02 mol/h/m2 at 225 A/m2 and As(V) was transported as H2AsO4 - with a rate of 0.01 mol/h/m2 in 0.5 mol/L of acid. At pH 2.8, the transport of As(V) increased tenfold to about 0.1 mol/h/m2. Antimony was transported through both anion and cation membranes at 2.7 and 3.4 mmol/h/m2, respectively. The transported cation is likely to be Sb(OH)2 + or SbO+ while the transported anions could be Sb(HSO4)m n- -type species