Construction of dual-functional membrane with novel structured β-cyclodextrin hybridization for simultaneous oily wastewater separation and hazardous aromatics removal

During the separation of water-insoluble oil droplets in the oily wastewater by the membrane treatment process, the simultaneous removal of organic pollutants dissolved in the aqueous phase remains a challenge. Herein, we demonstrate an effective strategy for preparing dual-functional membranes with hybridization of novel β-cyclodextrin (β-CD) derivatives to achieve complete cleansing of oily sewage. Alkylenedioxy bridged bis(p-difluoro-p-dicyano) phenyl substituted β-CDs (R3-2T-2β-CD and R6-2T-2β-CD) are first synthesized and incorporated into three frequently used membranes (polyethersulfone (PES), poly(p-phenylene terephthalamide) (PPTA) and poly(m-phenylene isophthalamide) (PMIA)) casting solutions to fabricate hybrid membranes, respectively. The hydrophilicity of the prepared membrane can be improved greatly for the separation of oil-in-water emulsions. The PMIA/R3-2T-2β-CD membrane exhibited pure water permeances over 760.50 L·m−2·h−1·bar−1 with separation efficiency of the tween 80 stabilized diesel-in-water emulsion above 98.62% under cross-flow filtration. Significantly, the hybrid membranes could concurrently remove naphthalene and methylene blue dissolved in water during oil-in-water separation. This study proves the application potential of cyclodextrins in designing membrane materials and these one-step hybrid membranes can thoroughly decontaminate oil-in-water emulsions by eliminating the dissolved polycyclic aromatic molecules.