The removal of toxic metals from liquid effluents by ion exchange resins. Part XIV: Indium(III)/H+/Dowex-400

Abstract

The removal of indium(III) from aqueous solutions by the cationic exchanger Dowex-400 has been investigated measuring the percentage of metal removal from the solution as a function of different resin dosages and pH values of the aqueous phase. The variation of the stirring speed (300–1000 min−1) applied to the system has a negligible effect on the removal of indium(III) from the solution; being the rate law associated to the ion exchange process best fitted to a film-diffusion controlled model. The exchange reaction is exothermic (ΔH°= -90 kJ·mol−1), and the kinetics models of the exchange process are temperature dependent: pseudo-first order at 20 °C, second order at 30 °C and pseudo-second order at 40 °C. The decrease of the aqueous pH value (from 1 to 0) decreases the percentage of metal removal from the solution. The metal uptake onto the resin is best represented by the Langmuir type-2 adsorption model. Indium(III) loaded onto the resin can be eluted by the use of acidic solutions, regenerating the resin at the same time.