In-depth insights on multi-ionic transport in Electrodialysis with bipolar membrane systems.

• Multi-ionic solutions in Electrodialysis with bipolar membrane (EDBM) were studied. • A new methodology for evaluating the ion transport in EDBM systems was proposed. • Apparent ion transport numbers and selectivities were calculated and discussed. • Enhanced chloride transport across AEMs and potassium across the CEMs were found. • Results showed SEC of 1.6 kWh kg−1 and current efficiency of 75% with real brines. Electrodialysis with Bipolar Membranes (EDBM) has become a key technology for valorising waste brine streams as a new chemical production route. Even though its application has been widely studied using single electrolyte solutions (e.g., NaCl or Na 2 SO 4), there is still a lack of knowledge about using multi-ionic mixtures. For the first time, this work aims to evaluate the EDBM performance when treating synthetic solutions mimicking the waste brines produced in a integrated process for the valorisation of solar saltworks bitterns. The behaviour of a lab-scale EDBM unit was assessed using SUEZ ion exchange membranes (IEMs), operating at 300 A m−2, and the ion transport through IEMs was investigated, based on the calculation of apparent transport numbers and selectivities. The results highlighted that multi-ionic solutions barely affected the production of hydroxide ions. Chlorides were transported up to 7 times faster than sulphates across the anion-exchange membranes, while the cation-exchange membranes exhibited slightly higher selectivity for potassium than for sodium (∼1.2). The current efficiencies ranged between 70 % and 80 %, while a minimum specific energy consumption of 1.60 kWh kg-1 NaOH was obtained for the most concentrated brine at 1 mol L-1 OH–. These results provide novel and valuable information to support the development and implementation of EDBM as a sustainable technology for supporting a resource-efficient and competitive economy through on-site and delocalized chemicals production routes. [ABSTRACT FROM AUTHOR]