Preparation Of Bipolar Membranes Modified Wtihe Graphene Oxide And Metal Ion

Bipolar membrane is a special functional membrane,which is compared of cation exchange layer,intermediate layer and anion exchange layer.Water molecules can be spiltted into H+ and OH-by using bipolar membrane.Currently,bipolar membrane electrodialysis is mainly limited by high price and energy consumption.In order to improve the production capacity and reduce the transmembrane voltage drop,cation exchange membrane was sprayed with graphene oxide or its coordination complex with Fe3+ or Cr3+ or Sn4+,followed by spraying polyethyleneimine(PEI)crosslinked with glutaraldehyde(GA)as anion exchange layer.The research results show the metal ion-modified graphene oxide bipolar membrane has a lower transmembrane voltage drop.The study found spraying 1 wt%PEI with 5400 ?L and 1 wt%GA with 1800 ?L was appropriate membrane-forming conditions of anion exchange layer.It was found that Sn-modified graphene oxide bipolar membrane had a lower transmembrane voltage drop of 0.98 V at 100 mA·cm-2;XPS results indicated metal ion was respectively assembled in the relative membrane.FTIR spectra showed PEI was successfully crosslinked with GA.SEM pictures showed that the cation exchange layer was closely contact with the anion exchange membrane.Moreover,such layer showed defect-free feacture.AC impedance spectroscopy demonstrated that the intermediate layer was ultra-thin at namometer scale.The measurements of contact angles showed the hydrophilicity of cation exchange membrane sprayed with GO and M-GO increased with the increasing the spraying amount.Meanwhile,the membrane hydrophilicity modified by metal ion was better than that metal-free modification.The swelling degree analyses demonstrated that the prepared bipolar membrane offered low swelling degree and high acid and base resistance.The electrodialysis experiments indicated that than compared with GO-modified membrane,M-GO bipolar membrane further improved the ability of producing acid and base.More importantly,the stability test showed that the graphene oxide could fix metal ions to prevent its loss.