L-lysine functionalized Ti3C2Tx coated polyurethane sponge for high-throughput oil–water separation

Abstract

Creating an efficient method that can provide simple, practical and high-throughput separation of oil–water mixtures has proved extremely challenging. Two-dimensional layered Ti3C2Tx MXene material with excellent hydrophilicity has attracted substantial attention for oil–water separation. However, conventional Ti3C2Tx separation membranes are susceptible to contamination by oil due to its relatively high adhesion to oil, hindering its practical applications in high-efficiency oil–water separation. To make Ti3C2Tx have underwater superoleophobicity and low oil adhesion, the surface of Ti3C2Tx can be modified by introducing hydrophilic groups. Herein, L-lysine functionalized Ti3C2Tx (Ti3C2Tx-Ly) was firstly prepared by decorating L-lysine on Ti3C2Tx through electrostatic interaction and hydrogen bonding. A facile dip-coating method is then used to coat polyurethane (PU) sponge with Ti3C2Tx-Ly, obtaining a superhydrophilic/underwater superoleophobic Ti3C2Tx-Ly @PU sponge. Owing to the excellent underwater superoleophobicity resulting from hydrophilic groups (–OH、–NH3) on the surface of Ti3C2Tx-Ly nanosheets and the enlarged interlayer spacing of Ti3C2Tx, the Ti3C2Tx-Ly @PU sponges demonstrated outstanding separation performance for a series of oil–water mixtures. Specifically, the Ti3C2Tx-Ly @PU sponge exhibits low oil adhesion and superhydrophilic (WCA = 0°)/submerged superoleophobic (UOCA > 155°) properties. The Ti3C2Tx-Ly @PU sponges displayed the best separation performance for cyclohexane/water mixture, and the maximum permeation flux is up to 221892 L m–2 h–1, accompanied by a remarkable separation efficiency of higher than 99.2% after 100 cycles. The permeation flux has exceeded most of the previous reported multifunctional separation membranes. In addition, the Ti3C2Tx-Ly @PU sponge also showed excellent separation performance for high-density oil dichloromethane/water with a separation efficiency over 99.4%. Of note, the Ti3C2Tx-Ly @PU sponge features excellent chemical stability to corrosive media, such as acidic, alkaline, and high salt solutions, possessing great potential for real-world applications. Furthermore, the as-prepared Ti3C2Tx-Ly @PU sponge exhibits rapid and efficient separation of oil-water mixtures through a fully gravity-driven process, which makes it a good candidate for industrial oil-contaminated water treatment and oil spill clean-up, and also provides new insights into the design and development of functional Ti3C2Tx through L-lysine modification. Therefore, this work reports a facile and promising way to fabricate scalable superhydrophilic/underwater superoleophobic sponge material for highly efficient oil–water separation.