Asymmetrically porous anion exchange membranes for acid recovery by diffusion dialysis are prepared by one-step functionalization of chloromethylated polysulfone (PSF) ultrafiltration membrane via reaction with N,N,N',N'-tetramethyl-1,3-propanediamine (TMPDA) to achieve simultaneous crosslinking and quaternization. The performance of the resulting TMPDA modified PSF (TPSF) membranes can be easily tailored by controlling the reaction time in TMPDA solution and thus the charged density and crosslinking degree. The TPSF membranes exhibit excellent diffusion dialysis performance, especially high acid dialysis coefficient, stemming from the porous matrix and thin selective layer (< 0.6 mu m). The optimized TPSF membrane has an acid dialysis coefficient of 0.065 m h(-1) and a separation factor of 34.0, which are 6.6 and 0.84 times greater than the corresponding values of the commercial DF-120 membranes at the same testing condition using a mixture of HCl and FeCl2 solution as feed solution. The membranes reported in this work are promising for scale-up for industrial acid recovery applications.