Preparation of heterogeneous cation exchange membrane and its contributions in enhancing the removal of Ni2+ by capacitive deionization system

Abstract

Capacitive deionization (CDI), an emerging method to eliminate ions from water at a low cost, has garnered significant interest in recent years. This study evaluates the implication of cation exchange resin loading on the membrane via the nonsolvent-induced phase inversion method. After determining the quantity of resins efficiently loaded on the membrane, it was subsequently utilized as a cation exchange membrane in the membrane capacitive deionization (MCDI) unit to examine the performance removal of Ni2+. The results show that the amount of resins influenced the membrane structure and significantly improved the efficiency of Ni2+ removal. The sulfonic acid group show a strong intensity directly proportional to the quantity of resins based on the FTIR measurement. In conjunction with the enhanced resin amount, ion exchange capacity and water content were increased. Simultaneously, there was an observed elevation in the water contact angle and the roughness of the membrane surface with increased resin amount. In the MCDI unit, membrane M20 (20% by weight resin) was employed to elucidate its roles in the CDI unit, encompassing an examination of various concentrations and flow rates, with Ni2+ utilized as a test contaminant. The results demonstrated that using membrane M20 in the MCDI (MCDI-M20) unit consistently exhibited higher adsorption levels than the CDI unit, reaching 19.80 mg g−1 ACC in the MCDI-M20 unit, while CDI unit achieved 10.27 mg g−1 ACC at 200 mg L−1 Ni2+ concentration and a flow rate of 10 mL min−1 at 1.2 V. Additionally, Ni2+ concentrations and flow rates in CDI system had an evident impact on the duration of adsorption due to the mechanisms of ions transport on the membrane. This study suggests that employing the prepared membrane in the MCDI unit enhanced the removal of Ni2+ from the solution, contributing to sustainable development goals.