Semi-interpenetrating polymer network anion exchange membranes based on quaternized polybenzoxazine and poly(vinyl alcohol-co-ethylene) for acid recovery by diffusion dialysis.

ABSTRACT

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. Four proportions of semi-IPNs exhibit clear micro-phase separation, which is conducive to ion transport. The water uptake of the four semi-IPNs ranges from 14.2% to 19.2%, while the swelling ratio 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-IPN46 to semi-IPN73 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 to 45.9, indicating the promising potential of the semi-IPNs.