β-Cyclodextrin-modified graphene oxide membranes with large adsorption capacity and high flux for efficient removal of bisphenol A from water

A novel beta-cyclodextrin (beta-CD) modified graphene oxide (CDGO) membrane with large adsorption capacity and high flux is developed for efficient removal of bisphenol A (BPA), which is an environmental endocrine disruptor that can affect human health. The CDGO membranes are fabricated by stacking CDGO nanosheets on porous substrates via vacuum filtration, and the CDGO nanosheets are fabricated by chemically grafting beta-CD molecules onto both sides of GO nanosheets. Because beta-CD molecules can form stable complexes with BPA molecules through host-guest recognition, the proposed CDGO membranes are featured with high efficiency for BPA removal. The water fluxes through CDGO membranes increase linearly with increasing the operating pressure, which confirms the CDGO membrane structures are stable during operations. With BPA rejection efficiency of about 100%, the fluxes of our CDGO membranes are one or two order of magnitudes higher than those of the RO and NF membranes previously used for BPA removal. The BPA adsorption capacities of our CDGO membranes are several times higher than those of the affinity membranes previously used for BPA removal, due to the high grafting density of beta-CD molecules on both sides of CDGO nanosheets, the enormous surface areas of CDGO nanosheets and the winding 2D nanochannels in CDGO membranes. Furthermore, the CDGO membranes can be regenerated easily by washing with ethanol, and the BPA removal efficiency can be recovered back to nearly 100% even after several repeated running cycles. The proposed membranes with high flux and large adsorption capacity are highly promising in applications in the field of water treatments and molecular separations.