Cross-linking to prepare composite graphene oxide-framework membranes with high-flux for dyes and heavy metal ions removal

- GO-IPDI membranes with high flux and excellent rejection for dyes were prepared.
- The retention performance was excellent for organic dyes, and moderate for heavy metal ions.
- Physical sieving nano-channel was mainly contributed to the rejection of dyes.
- The decreased interaction force was the main reason for the retention of heavy metal ions.

Although graphene oxide framework-based membranes separation represent an effective and potential process in water purification and desalination, instability and low flux of the membrane make them still challenging in industrial application. Herein, isophorone diisocyanate (IPDI) was selected as cross-linking for covalent modification of graphene oxide nanosheets to design the newly graphene oxide-framework membranes (GOF) by a facile vacuum-assisted filtration method. The cross-linked GO-IPDI membrane can be used to effectively remove dyes and heavy metals via filtration. Results of filtration experiments and microstructure characterization confirmed that IPDI cross-linking GO not only enhanced structural stability but also enlarged the nano-channels among GO sheets for higher water permeability. The GO-IPDI membrane exhibited a high flux of 80-100 L m−2 h−1 bar−1 under an extremely low external pressure (1.0 bar). It exhibited a high rejection rate (above 96%) for dyes including methylene blue, methylene orange and rhodamine-B and congo red. While the retention was moderate for Pb2+, Cu2+, Cd2+, Cr3+ ranging from 40% to 70%. These results demonstrated the potential application of GO-IPDI in wastewater and provided a novelty way of design and fabrication of high water permeability and excellent separation performance of graphene-based membranes product.

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