An Investigation of a (vinylbenzyl) trimethylammonium and N-vinylimidazole-substituted poly (vinylidene fluoride-co-hexafluoropropylene) copolymer as an anion-exchange membrane in a lignin-oxidising electrolyser

Electrolysis is seen as a promising route for the production of hydrogen from water, as part of a move to a wider “hydrogen economy”. The electro-oxidation of renewable feedstocks offers an alternative anode couple to the (high-overpotential) electrochemical oxygen evolution reaction for developing low-voltage electrolysers. Meanwhile, the exploration of new membrane materials is also important in order to try and reduce the capital costs of electrolysers. In this work, we synthesise and characterise a previously unreported anion-exchange membrane consisting of a fluorinated polymer backbone grafted with imidazole and trimethylammonium units as the ion-conducting moieties. We then investigate the use of this membrane in a lignin-oxidising electrolyser. The new membrane performs comparably to a commercially-available anion-exchange membrane (Fumapem) for this purpose over short timescales (delivering current densities of 4.4 mA cm−2 for lignin oxidation at a cell potential of 1.2 V at 70 °C during linear sweep voltammetry), but membrane durability was found to be a significant issue over extended testing durations. This work therefore suggests that membranes of the sort described herein might be usefully employed for lignin electrolysis applications if their robustness can be improved

Comparative Studies on Electro-Membrane Processes for Recovery of Ascorbic Acid from its Sodium Salt

This article presents an efficient electro-membrane reactor with three compartments (EMR-3) for in situ ion substitution and recovery of ascorbic acid (ASH) from its sodium salt (ASNa). In situ ion substitution, separation, and recovery of ASH from ASNa were achieved by EMR-3 using the ion-exchange membranes (cation-exchange membranes: CEMs), based on the principle of electro-electrodialysis. Process performances of EMR-3 and electrodialysis (ED) were compared. Under optimum operating conditions for EMR-3 at 3.0 V cm −1 applied voltage (after passage of 3.41 × 10 3 Coulombs), current efficiency (CE), and energy consumption (W) were found to be 94.3% and 2.63 kWh kg −1 , respectively, corresponding to 95% recovery of ASH. While by ED, under the similar experimental conditions, CE and W were found to be 59.1% and 5.44 kWh kg −1 , respectively corresponding to 86.3% recovery of ASH. It was concluded that EMR-3 showed high CE, recovery, and low W, in comparison with ED under similar experimental conditions. Thus the proposed EMR-3 is an efficient alternate for producing ASH from ASNa in an by economical and environmentally-friendly manner. Also, the production of NaOH in cathode stream is a spinoff of EMR-3

Graphene Oxide–Polyaniline as a Water Dissociation Catalyst in the Interfacial Layer of Bipolar Membrane for Energy-Saving Production of Carboxylic Acids from Carboxylates by Electrodialysis

Bipolar membrane (BPM) was prepared by layer-by-layer casting of the cation-exchange layer (CEL; sulfonated poly­(2,6-dimethyl-1,4-phenylene oxide) (SPPO), interfacial layer (IL), and anion-exchange layer (AEL; quaternized PPO) in the same solvent to achieve good adhesion. Graphene oxide-polyaniline composite (GO-PANI) was introduced in the IL of BPM as water dissociation (WD) catalyst. Under applied reverse bias, water molecules in the IL zone dissociate and generate H⁺ and OH^– useful electrosynthesis by BPM electrodialysis (BPMED). Prepared BPM was assessed by current–voltage (<i>i</i>–<i>V</i>) curves and performance of BPMED for converting homologues carboxylates into their corresponding acid and base. Under the operating conditions in BPMED, 71–63% recovery of the different carboxylic acids was recorded with 92–97% CE and 0.90–0.98 kWh kg^–1 energy consumption. Negligible co-ion leakage across the BPM also revealed its efficient nature and product (carboxylic acid) purity. Additionally, low and stable <i>V</i>_diss (0.77−1.12 V) in equilibrium with different carboxylates is responsible for the low energy consumption and making viable high-performance BPM