Electrodialysis with Bipolar Membranes for the Generation of NaOH and HCl Solutions from Brines: An Inter-Laboratory Evaluation of Thin and Ultrathin Non-Woven Cloth-Based Ion-Exchange Membranes

Abstract

SEArcularMINE project aims to recover critical raw materials (CRMs) from brines from saltworks, thus facing the CRM shortage within Europe. To promote a fully circular scheme, the project valorises concentrated brines using Electrodialysis with Bipolar Membranes (EDBM) to generate the required amounts of reactants (i.e., acids and bases). The performance of new non-woven cloth ion exchange membranes (Suez): i) an ultra-thin non-woven polyester cloth, and ii) a thin poly-propylene cloth acting as their support structure was assessed. Additionally, the anion layer in-cludes a catalyst to promote the water dissociation reaction. The effect of current density (100, 200 and 300 A m-2) on the performance of two combinations of membranes in an inter-laboratory exercise using 2 M NaCl was evaluated. According to statistical analysis ANOVA, there was an agreement on the results obtained in both laboratories. NaOH/HCl solutions up to 0.8 M were generated working at 300 A m-2 using both combinations of membranes. Regarding performance parameters, stack set-ups incorporating ultra-thin polypropylene membranes showed lower Specific Energy Consumption (SEC) and higher Specific Productivity (SP) than thin polypropylene ones. Hence, ultra-thin polypropylene membranes reported SEC between 2.18 and 1.69 kWh kg-1NaOH and SP between 974 and 314 kg m-2 y-1.