BPPO-based anion exchange membranes for acid recovery via diffusion dialysis

Diffusion dialysis (DD) with anion exchange membranes (AEMs) as the core component is an ideal technology for acid recovery from acidic wastewater. Herein, a series of TEA–BPPO AEMs were prepared from triethanolamine (TEA) and brominated polyphenylene ether (BPPO) using the solution casting method. The structures of the prepared membranes were characterized and analyzed through nuclear magnetic resonance hydrogen spectroscopy (¹H NMR), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM). In addition, the properties of the membranes, such as ion exchange capacity (IEC), linear swelling rate (LSR), water uptake (W_U), chemical stability, thermal stability and mechanical stability, were explored. In DD experiments, the optimal AEM (i.e., TEA–BPPO–M80) applied to simulate acid recovery from a mixed HCl (1 mol L⁻¹)/FeCl₂ (0.2 mol L⁻¹) solution exhibited an acid dialysis coefficient (U_H⁺) of 0.0629 m h⁻¹ and separation factor (S) of 97.78, which were significantly better than those of the commercial membrane DF-120. In addition, the TEA–BPPO–M80 AEM exhibited excellent thermal stability and acid resistance. In summary, the prepared membranes possess great potential for application in DD acid recovery.