Semi‐Interpenetrating Polymer Network Anion Exchange Membranes Based on Quaternized Polybenzoxazine and Poly(Vinyl Alcohol‐Co‐Ethylene) for Acid Recovery by Diffusion Dialysis

Acid recovery from acidic waste is a pressing issue in current times. Chemical methods for recovery are not economically feasible and require significant energy input to save the environment. This study reported a semi‐interpenetrating polymer network (semi‐IPN) anion exchange membranes (AEMs) for acid recovery by diffusion dialysis with excellent dimensional stability, high oxidation stability, good acid dialysis coefficient (UH+) and high separation factor (S). Semi‐IPN AEMs are prepared by ring‐open cross‐linked quaternized polybenzoxazine (AQBZ) with poly(vinyl alcohol‐co‐ethylene), where AQBZ is obtained by Mannich reaction and Menshutkin reaction. All four proportions of semi‐IPNs exhibit clear micro‐phase separation, which is conducive to ion transport. The water uptake (WU) of the four semi‐IPNs ranges from 14.2 % to 19.2 %, while the swelling ratio (SR) remains between 8.7 % and 11.3 %. These results indicate that the cross‐linked structure in the designed semi‐IPNs effectively control swelling and ensure dimensional stability. The thermal degradation temperature (Td5) of semi‐IPN4:6 to semi‐IPN7:3 varies from 309 °C to 289 °C, with an oxidation stability weight loss rate (WOX) ranging from 91.5 % to 93.5 %, demonstrating excellent thermal stability and oxidation stability. The semi‐IPNs also show good UH+ values ranging from 11.9–16.3*10−3 m/h and high S values between 38.6 and 45.9, indicating the promising potential of the semi‐IPNs. Semi‐IPN AEMs are prepared by ring‐open cross‐linked quaternized polybenzoxazine with poly(vinyl alcohol‐co‐ethylene) exhibted excellent dimensional stability, high oxidation stability, good acid dialysis coefficient (UH+) and high separation factor (S).