Integration of Bipolar Membrane Electrodialysis with Ion-Exchange Absorption for High-Quality H3PO2 Recovery from NaH2PO2.

Abstract

H3PO2 has emerged as an indispensable reducing agent for electroless nickel plating. Commercial preparation of H3PO2, with high purity and low cost, is a great challenge. In this work, a novel technique by the integration of bipolar membrane electrodialysis (BMED) with ion-exchange absorption was designed to prepare high-quality H3PO2 aqueous solution. The critical parameters, such as voltage drop, NaH2PO2 concentration, and different types of anion-exchange membranes, were systematically investigated. Continuous experiments indicated that a high yield of up to 80.06% with a low energy consumption of 4.99 kW h/kg was achieved under optimal operation conditions (voltage drop of 20 V, feed concentration of 15 wt % NaH2PO2, and anion-exchange membrane of AHA). Moreover, leakage of Na+ ions through the bipolar membrane was observed. By using T-52H cation-exchange resin, the final concentration of Na+ ions in H3PO2 aqueous solution was reduced to 20.91 mg/L. Subsequently, a long-term experiment was performed to evaluate the stability of the BMED stack, and the concentration of H3PO2 in the acid compartment reached 4.15 mol/L. Under optimal conditions, the H3PO2 production cost was estimated at $0.937 kg–1, which was competitive and economically friendly for industrial application.