Graphene oxide modified porous anion exchange membranes for acid recovery through diffusion dialysis

Graphene oxide (GO) - P84 co-polyimide composite membranes are prepared through vacuum filtrating of GO on the porous P84 anion exchange supports, followed by crosslinking with ethylenediamine. The cross-linking provides the stacked GO nanosheets with the necessary stability to overcome their inherent dispersibility in water environment. The membranes are first applied to the diffusion dialysis process to separate H2SO4 from the H2SO4/FeSO4 mixed feed. The dialysis coefficient (U-H2SO4) for the H2SO4 is 0.0083-0.011 m/h, and the H+/Fe2+ separation factor (S-H2SO4) is 8.0-10.8, both of which are higher than the values of the commercial membrane S203 (similar to 0.0018 m/h, similar to 8). The S-H2SO4 value is also higher than that of the P84 support membrane (similar to 5.4), showing that the selectivity of the GO-P84 composite membranes is obviously improved. Besides, the membranes are used to separate HCl from the organic acidic liquor containing HCl/glyphosate, which is produced largely from the preparation process of glyphosate pesticide. Results show that the dialysis coefficient of the HCl (U-HCl) is ranging from 0.0065 to 0.0081 m/h, and the HCl/glyphosate separation factor (S-HCl/Gly) is 8.5-11.4. In contrast, the U-HCl and S-HCl/Gly values of the P84 porous support membrane are 0.0097 m/h and 4.8, respectively. What's more, the composite membranes show less water osmosis. The results further indicate that the GO-P84 composite membranes have good separation ability for the acidic solutions.