Asymmetrically porous anion exchange membranes with an ultrathin selective layer for rapid acid recovery

Diffusion dialysis for acid recovery from acidic waste solution suffers from the low process capacity due to low proton permeability of current dense anion exchange membranes. In this work, asymmetrically porous ultrafiltration membranes with a thin skin layer (e.g., < 1 micrometer) were converted to diffusion dialysis membranes with a hierarchically porous structure after in situ crosslinking and quaternization. Except for good thermal and chemical stabilities, the resulting membranes exhibited an acid permeability coefficient as high as 0.041-0.062 m h(-1) and a separation factor of 30.4-84.4, which are 4.1-6.3 times and 0.6-3.6 times higher than the commercial DF-120 membrane, respectively. The acid recovery capacity can be enhanced from 11.3 to 82.4 L m(-2) d(-1), with a 64% increase in acid purity when our new membrane was used to replace the commercial DF-120 membrane. Moreover, these results are also superior to most of the reported membranes. Therefore, the excellent performance and simple preparation process endow our new diffusion dialysis membranes with great potential for high-efficiency industrial acid recovery applications. (C) 2016 Elsevier B.V. All rights reserved.