Flower-like ZnO modified TiO2@Ti3C2Tx composite for efficient adsorption of malachite green and oil-water separation

The intensification of industrial production has led to a sharp increase in the discharge of toxic organic chemicals and wastewater from printing and dyeing industry. In this study, flower-like ZnO modified TiO2@Ti3C2Tx composites (ZnO/TiO2@Ti3C2Tx) were prepared by in-situ oxidation solvothermal method from zinc nitrate hexahydrate and tetramethylammonium hydroxide intercalated Ti3C2Tx. During the solvothermal processes, sodium hydroxide acted as an etchant to further exfoliated the accordion-like Ti3C2Tx into single or few-layer; and at the same time, TiO2 was formed in-situ on the surface of Ti3C2Tx with simultaneous deposition of flower-like ZnO. The layer structural Ti3C2Tx facilitates the loading and dispersion of ZnO and TiO2 on its surface. After the in-situ oxidation by solvothermal method, TiO2 was evenly distributed on the surface of Ti3C2Tx, adjusting the functional groups on the surface of the ZnO/TiO2@Ti3C2Tx composite, and improving its adsorption performance. ZnO/TiO2@Ti3C2Tx can be used as an efficient adsorbent for malachite green with a high maximum adsorption capacity of 1232.7 mg g−1, which is higher than that of TiO2@Ti3C2Tx (628.57 mg g−1). Moreover, a superhydrophilic and underwater superoleophobic ZnO/TiO2@Ti3C2Tx@PU sponge was prepared by loading ZnO/TiO2@Ti3C2Tx onto polyurethane (PU) sponge. The introduction of ZnO enhances the surface roughness of the ZnO/TiO2@Ti3C2Tx@PU sponge, which can effectively separate six oil-water mixtures, and has a high separation flux of 171784 L m−2 h−1 and separation efficiency of 99.6% for cyclohexane-water mixture.