Removal of pollutants via synergy of adsorption and photocatalysis over MXene-based nanocomposites

Abstract

The MXene-based nanocomposites comprised by multi-layered Ti3C2-MXene (ML-Ti3C2) nanosheets and transition metal oxide (TMO) nanomaterials, i.e. zinc oxide (ZnO), bismuth molybdate (Bi2MoO6) and tin dioxide (SnO2), were prepared in this work. After loading ML-Ti3C2 MXene, the contact angle of oleophobic ZnO, Bi2MoO6, and SnO2 for oil drop decreases to 98°, 62°, and 75°, respectively. The improvement of lipophilicity of the composites is conducive to the adsorption of water-soluble organic pollutants. Coupling of MXene enhances the adsorption capacity of the composite catalyst for pollutants. The adsorption capacities of ZnO/ML-Ti3C2, SnO2/ML-Ti3C2 and Bi2MoO6/ML-Ti3C2 for methylene blue (MB) molecules are 155 mg/g, 163 mg/g and 152 mg/g, respectively. The adsorption of MB on ML-Ti3C2 based nanocomposites follows the Langmuir model, indicating that the monolayer covering of the nanocomposites is the main adsorption mechanism. Under visible-light irradiation, 150 mg/L of high concentration MB solution and 20 mg/L of 4-chlorophenol (4-CP) solution could be completely removed by adsorption and photocatalysis over ZnO/ML-Ti3C2 for 4 h. The electron spin resonance (ESR) trapping method and free radical scavenger experiments both show that hydroxyl radicals and superoxide free radicals are reactive species in the degradation process. The photoluminescence (PL) spectrum analysis shows that coupling TMO and MXene inhibits the recombination of photogenerated electron-hole pairs. The synergistic removal of pollutants by strong adsorption and visible photocatalysis of MXene-based nanocomposites provides a new idea for environmental pollution control.

Keywords

• Zinc oxide
• Bismuth molybdate
• Tin dioxide
• MXene
• Photocatalysis