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

The SEArcularMINE project aims to recover critical raw materials (CRMs) from brines from saltworks, thus facing a 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). Regarding the performances of new non-woven cloth ion-exchange membranes (Suez): (i) an ultra-thin non-woven polyester cloth and (ii) a thin polypropylene cloth acting as the support structures were assessed. Additionally, the anion layer includes 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 the performance parameters, stack set-ups incorporating thin polypropylene membranes showed lower specific energy consumption (SEC) and higher specific productivity (SP) than ultra-thin polypropylene ones. Hence, for ultra-thin polypropylene membranes, SEC was reported to be between 2.18 and 1.69 kWh kg−1NaOH and SP between 974 and 314 kg m−2 y−1.

Maximizing Marine Carbon Removal by Coupling Electrochemical and Biological Methods

“…In general, our system had higher inefficiencies compared to that reported in the literature. This could be partly due to our operation with natural seawater versus previously studied NaCl or synthetic seawater feed solutions. , Note that we used the BPMED unit purely to generate the acid stream for algae growth. The optimization of BPMED was not the focus, as the system performance and energy consumption are outside the boundary of our CO 2 emissions analysis and do not impact the final conclusions from this study.…”

Chromium-Modified Heterogeneous Bipolar Membrane: Structure, Characteristics, and Practical Application in Electrodialysis

“…This is one of the problems of standard anion-exchange membranes. To solve this problem, research is being conducted on the development of anion-exchange membranes with proton blocking properties [ 42 ].…”

Acid/Base Production via Bipolar Membrane Electrodialysis: Brine Feed Streams to Reduce Fresh Water Consumption

“…All experiments were carried out in batch mode, applying a current density of 300 A m –2 . This was found based on previous works to be sufficient to exceed the concentration of 1.0 mol L –1 in both acid and base compartments . The duration of the tests was 240 min for the Fumatech stack and 85 min for the SUEZ stack, which were chosen to exceed 1.0 mol L –1 OH – concentration in the alkaline compartment.…”

“…This was found based on previous works to be sufficient to exceed the concentration of 1.0 mol L −1 in both acid and base compartments. 35 The duration of the tests was 240 min for the Fumatech stack and 85 min for the SUEZ stack, which were chosen to exceed 1.0 mol L −1 OH − concentration in the alkaline compartment. In fact, for the sake of comparison, tests were performed at the same applied current density and initial solution volumes.…”

“…Concentrations of 1.99 mol L −1 HCl and 2.14 mol L −1 NaOH along with a SEC value of 3.8 kWh kg −1 HCl were measured. More recently, Leoń et al 35 used new nonwoven cloth IEMs (SUEZ) assembled on a stack (280 cm 2 effective area, 5 triplets). Final concentrations of 1.77 mol L −1 HCl and 1.25 mol L −1 NaOH from 2 mol L −1 NaCl under a current density of 300 A m −2 with a SEC value of 3.29 kWh kg −1 NaOH and a CE of 49% were achieved.…”