Acid and alkaline production from multi-ionic brines via Electrodialysis with Bipolar Membranes

Abstract

In recent years, a great attention has grown towards the brine valorization through chemicals production and mineral recovery as an alternative to conventional disposal. Electrodialysis with Bipolar Membranes (EDBM) is an emerging process that can be used for the production of alkaline and acidic solutions from salt solutions. Within the SEArcularMINE project framework, the exploitation of saltworks bitterns (highly concentrated solutions generated during the sea-salt production process) is proposed for minerals recovery and NaOH and HCl solutions production. In this work, an EDBM unit, equipped with commercial ion exchange membranes, was tested for the first time in closed-loop mode with: (i) single NaCl solutions as reference case (ii) synthetic brines including NaCl, Na2SO4, and KCl salts, and (iii) real saltwork brines, which contains traces of other minor elements. Different scenarios were assumed in terms of feed compositions to study the effect on process performance parameters as specific energy consumption (SEC), acid and base solutions purities, current efficiency, and yield. Main results at laboratory-scale unit highlights the process feasibility to produce alkaline solutions at target concentrations exceeding 1M NaOH equivalent, while maintaining high product purities and current efficiencies.