Construction of robust silica-titania polydopamine composite membrane with light-absorption property for photothermal vacuum membrane distillation

Abstract

A robust silica-titania polydopamine composite membrane was fabricated adding a photothermal polydopamine coating to the surface of polypropylene membrane for photothermal vacuum membrane distillation. Detailly, the surface of an inert PP membrane was modified with atomically controllable titanium and silicon to enhance the hydroxyl groups on the membrane surface, then, a photothermal effect layer of polydopamine was generated on the composite membrane surface through the self-polymerization reaction of dopamine. The polydopamine coating has significant light absorption and heating properties, and it can act as a local heater when exposed to light sources. This local heating effect significantly raises the temperature at the membrane interface, creating a thermal gradient that drives the evaporation of water molecules. Specifically, we quantitatively analyzed the three reasons (surface energy, free radicals, and photothermal effect) for the increase in evaporation rate of the pristion PP membrane caused by the membrane composite membrane. Among these reasons, the photothermal effect caused by black polydopamine is the most important factor for improving evaporation efficiency. The dark-illumination alternating experiment revealed that the PP-TiO2-SiO2-PDA composite membrane delivered a noteworthy enhancement in vacuum membrane distillation performance (approximately 40%), while the improvement of the PP membrane was only 1.7%.