In situ bridges of nano-titanium dioxide constructed in MXene self-cleaning loose nanofiltration membranes for dye wastewater treatment

Abstract

It has been a longstanding problem to combat the oxidation process of MXene membranes. Here, we propose a strategy to construct nano bridge defect repair loose nanofiltration membrane with the help of MXene oxidation. The oxidation kinetics of Ti3C2Tx was investigated in both model and experimental aspects. The acid solution leads to aggregation and smaller d-spacing. However, the oxidation of MXene was accelerated in alkaline solution via reaction with hydroxyl anions resulting in a hydrophilic MXene membrane surface. The water permeability of the pH = 12-Ti3C2Tx membrane increased to a maximum value of 26.5 L·m−2·h−1·bar−1 together with a high rejection (98 %) of Janus green B (JGB). Titanium dioxide, which was in situ formed by oxidation of MXene, gives the membrane self-cleaning properties under UV light. The water recovery ratio was as high as 96.6 %. To further study the mechanism of in situ oxidation of MXene to form nano-titanium dioxide, the oxidation stages were analyzed which revealed that the in-situ oxidation process involved three different oxidations stages. This research offers a new perspective on MXene membrane design, paving the way for a new method of in situ nano bridge defect repair loose MXene nanofiltration membrane.