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Herein, the effect of electrolyte composition (single vs salt mixture) on the performance of reverse electrodialysis (RED) has been investigated using lab-made sulfonated poly(ether ether ketone) (sPEEK) cation exchange membrane (CE) membrane and Neosepta, a commercially available anion exchange (AE) membrane. The efficiency of the RED cell was monitored by measuring open-circuit voltage (OCV), power density (PD), and gross power density (PD gross ). The effect of feed solution flow and concentration was analyzed by using several electrolytes (LiCl, NaCl, KCl, and NH 4 Cl) and mixed composition (NaKCl and NaNH 4 Cl). NaCl solution among single electrolytes exhibited the highest performance with a PD of 1.77 Wm −2 , which was improved further by intermixing with KCl and NH 4 Cl. For the case of binary mixtures, NaNH 4 Cl showed a PD of 2.51 Wm −2 , which is 42% higher compared to that of NaCl possibly due to the inferior stack resistance. A molecular dynamics (MD) simulation was performed to further investigate the adsorption-diffusion properties of CEM and AEM at the molecular scale. A positive correlation was observed between MD simulation and experimental measurements regarding the competitive adsorption of cations into the sPEEK membrane with the following trend NH 4 + > K + > Na + > Li + , which is associated with the ionic radius and hydration energies of respective cations.

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.

High-performance electrochemical devices require a specific size of nanochannel in ion-exchange membranes for producing stable cell performance. We have tuned the size of the water nanochannel by varying the ion-exchange capacity of the membrane. It influences the current density of electrochemical devices. Here, we have demonstrated large-area dual-purpose membranes, implemented in reverse electrodialysis and fuel cell systems for generating power. The selectivity, compatibility, and flexibility of the membrane with the electrode are outstanding and have been explained in great detail. In this article, we have illustrated a novel combination of sPEEK/FAA-3 membranes for reverse electrodialysis applications as a cation and an anion. The membrane can freely withstand structural stability and durability at high temperatures under hydrated conditions and offers excellent results in the fuel cell. We achieve superior performance for both fuel cells and reverse electrodialysis cells without altering the device architecture. Membranes with varying ion-exchange capacity (IEC) values and their electrochemical applications at one platform contribute to paving the path for enhancing the device performance.

Concentrated bitterns discharged from saltworks have extremely high salinity, often up to 300 g/L, thus their direct disposal not only has a harmful effect on the environment, but also generates a depletion of a potential resource of renewable energy. Here, reverse electrodialysis (RED), an emerging electrochemical membrane process, is proposed to capture and convert the salinity gradient power (SGP) intrinsically conveyed by these bitterns also aiming at the reduction of concentrated salty water disposal. A laboratory-scale RED unit has been adopted to study the SGP potential of such brines, testing ion exchange membranes from different suppliers and under different operating conditions. Membranes supplied by Fujifilm, Fumatech, and Suez were tested, and the results were compared. The unit was fed with synthetic hypersaline solution mimicking the concentration of natural bitterns (5 mol/L of NaCl) on one side, and with variable concentration of NaCl dilute solutions (0.01–0.1 mol/L) on the other. The influence of several operating parameters has also been assessed, including solutions flowrate and temperature. Increasing feed solutions’ temperature and velocity has been found to lower the stack resistance, which enhances the output performance of the RED stack. The maximum obtained power density (corrected to account for the effect of electrodic compartments, which can be very relevant in five cell pairs laboratory stacks) reached around 10.5 W/m2cellpair, with FUJIFILM Type 10 membranes, temperature of 40 °C, and a fluid velocity of 3 cm s−1 (as empty channel, considering 270 μm thickness). Notably, the present study results confirm the large potential for SGP generation from hypersaline brines, thus providing useful guidance for the harvesting of SGP in seawater saltworks all around the world.

Reverse electrodialysis (RED) generates power directly by transforming salinity gradient into electrical energy. The ion transport properties of the ion-exchange membranes need to be investigated deeply to improve the limiting efficiencies of the RED. The interaction between “counterions” and “ionic species” in the membrane requires a fundamental understanding of the phase separation process. Here, we report on sulfonated poly(vinylidene fluoride-co-hexafluoropropylene)/graphitic carbon nitride nanocomposites for RED application. We demonstrate that the rearrangement of the hydrophilic and hydrophobic domains in the semicrystalline polymer at a nanoscale level improves ion conduction. The rearrangement of the ionic species in polymer and “the functionalized nanosheet with ionic species” enhances the proton conduction in the hybrid membrane without a change in the structural integrity of the membrane. A detailed discussion has been provided on the membrane nanostructure, chemical configuration, structural robustness, surface morphology, and ion transport properties of the prepared hybrid membrane. Furthermore, the RED device was fabricated by combining synthesized cation exchange membrane with commercially available anion exchange membrane, NEOSEPTA, and a maximum power density of 0.2 W m−2 was successfully achieved under varying flow rates at the ambient condition.