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

Ti3C2Tx-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 Ti3C2Tx surface was used to obtain amino acid-modified Ti3C2Tx (L-CPT and L-HPT), respectively, by covalent and non-covalent bonds under mild conditions, enriching variety and number of hydrophilic groups on the Ti3C2Tx 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 Ti3C2Tx can functionally modify PU and PA substrates toseparate oily wastewater and dye wastewater, respectively.