Covalently grafted amino acid-modified Ti3C2Tx to construct an interface for separation of oily wastewater and dye wastewater

Ti 3 C 2 T x -based modified separation materials are widely used in the field of wastewater separation, but most of them have poor fluxes. Here, grafting of l -cysteine and l -histidine onto polydopamine-pretreated Ti 3 C 2 T x surface was used to obtain amino acid-modified Ti 3 C 2 T x (L-CPT and L-HPT), respectively, by covalent and non-covalent bonds under mild conditions, enriching variety and number of hydrophilic groups on the Ti 3 C 2 T x surface. Polyurethane sponge (PU) coated with L-CPT and L-HPT (L-CPTPU and L-HPTPU) exhibit excellent underwater oleophobicity and show impressive separation efficiency (>99.4%) for various oil-water mixtures. Especially, L-CPTPU and L-HPTPU achieved high-throughput separation for cyclohexane-water mixtures with maximum permeation fluxes of 220,319 and 222,197 L m -2  h -1 , respectively, and had excellent resistance to corrosive media. Besides, polyamide membranes modified with L-CPT and L-HPT (L-CPTPA and L-HPTPA) form abundant permeation channels, achieving high-efficiency separation for toluene in water emulsion with separation efficiency greater than 99.1%. In addition, L-CPTPA and L-HPTPA exhibited remarkable rejection (>99.1%) and high permeability (>1100 L m -2  h -1 bar -1 ) for 20 mg L -1 malachite green solution. Therefore, the amino acid-modified Ti 3 C 2 T x can functionally modify PU and PA substrates toseparate oily wastewater and dye wastewater, respectively.