Ion exchange membranes based on radiation-induced grafted functionalized polystyrene for high-performance reverse electrodialysis
Radiation-induced grafted ion exchange membranes based on functionalized polystyrene were tested for the first time in reverse electrodialysis (RED). Сation and anion exchange membranes based on sulfonated and quaternized/chloromethylated poly(styrene-co-divinylbenzene) grafted on UV-oxidized polymethylpentene films with different conductivity and selectivity relationships were compared with each other and with different commercial ion-exchange membranes (IEMs), FujiFim® Type 1 and Type 2 and RALEX®. The synthesized grafted membranes provided the highest power density of lab-scale stacks with a total active membrane area of 72 cm² with the use of 0.1 М/1 М NaCl (0.67 W m⁻²) and 0.1 М/5 М NaCl (2.1 W m⁻²) solutions. The use of grafted membranes with a low resistance ~0.5 Ω cm² (0.5 М NaCl, 25 °C) did not benefit the stack resistance; the low selectivity of such membranes resulted in a lower voltage and a high non-selective diffusion current of the RED stack. Higher power densities and current efficiencies in some model systems are observed for stacks with grafted membranes with lower conductivity and higher selectivity.