Internally cross-linked poly (2,6-dimethyl-1,4-phenylene ether) based anion exchange membrane for recovery of different acids by diffusion dialysis

Abstract

Acid recovery from acidic waste is a critical issue to be focused on nowadays. Chemical approaches for recovery are not commercially viable and energy intensive to save the environment. Here, we report internally cross-linked poly (2,6-dimethyl-1,4-phenylene ether) (PPE) based anion exchange membranes (AEMs) for acid recovery by diffusion dialysis, prepared via quick grafting of N-methyl-4-piperidone using ultrasonication. The prepared AEMs are assessed for their physicochemical parameters and depicted water uptake (WU) and ion-exchange capacity (IEC) in the range 22.00%–31.00% and 0.64 meq/g–2.18 meq/g respectively for Cl−1, NO3− and SO42− ions. AEMs were investigated for recovery of hydrochloric acid (HCl), nitric acid (HNO3) and sulphuric acid (H2SO4) from simulated effluent based on their proton diffusion coefficient (UH+), separation factor (S) and recovery efficiency (Ƞ). These membranes illustrated the proton diffusion coefficient as high as 0.065 m h−1 and enhanced separation factor values up to 132 at 27 °C. Recovery performance for different acids is corroborated based on unique self-organized membrane structure, studied using AFM phase imaging and cumulative influence of bulk diffusion coefficient, ion-exchange capacity, and hydration radii of Cl−1, NO3− and SO42− ions. The acid recovery efficiency illustrated the trend HCl > HNO3 > H2SO4. The hydrate (–OH) functionality with a non-overlapping set of lone pairs on oxygen enhances the proton mobility via Grotthuss mechanism inside the membrane matrix and provides a cradle-like pathway for high proton mobility. The results are pronounced for fabricated membranes compared to commercially available standards for acid recovery via diffusion dialysis.