Slide-shaped cotton-based photocatalytic solar evaporator with dual mutually strengthening functions for simultaneous desalination and dynamic fast dye removal

Abstract

High-salt dyeing wastewater would do harm to both the environment and people's health. Herein, a photocatalytic solar evaporator with bifunctions of photothermal evaporation and photocatalysis was prepared by loading MnO2 and TiO2 on the cotton fabric, aiming at simultaneous pure water derivation and dye degradation. The evaporator was positioned in a slide-shaped configuration that uses downward capillary force and gravity-assisted water transportation for a sufficient water supply, avoiding salt accumulation during photothermal evaporation and realizing a fast dynamic dye removal via photocatalysis. Interestingly, the loaded TiO2 enhances the photothermal activity of the loaded MnO2 by increasing light absorption. While MnO2 also enhances the photocatalytic activity of TiO2 by charge transfer and heat generation. It was exciting to find that the solution streaming down dynamically through the slide-shaped evaporator into the downstream container was completely colorless, which was in sharp contrast with the blue dye solution at the upstream. Under one sunlight, the evaporator showed a evaporation rate of 1.65 kg m−2 h−1, a photothermal conversion efficiency of 96.65 % and a methylene blue removal efficiency of >95 % during the 8-day evaporation. This study realizes the synergistic effect of photothermal evaporation and photocatalysis, providing a novel strategy for the treatment of high-salt dyeing wastewaters.