Water desalination using visible light by disperse red 1 modified PTFE membrane

Abstract

Water purification and seawater desalination are current desired technologies because global water shortage becomes more serious. As this problem is related to global warming, the energy for the processes should be covered by renewable energies like solar light. It was found recently that water droplets on azobenzene modified anodized alumina membranes permeate the membrane under light irradiation to be purified and desalinated. This paper reports an advanced system of the light induced water treatment, where disperse red 1 (DR1) modified PTFE (polytetrafluoroethylene) membranes are employed. Hydrophobic PTFE membrane inhibits the natural infiltration of raw water into the membrane to prevent the contamination of treated water. Disperse red 1 photo-isomerizes only with visible light to adopt to the utilization of solar light. Waters on the DR1 modified PTFE membrane penetrated the membrane under visible light irradiation. 3.5% NaCl solution was desalinated to purified water (<0.01% NaCl) by the membrane permeation process. A simulated solar light of a solar simulator was very effective for this desalination to produce clarified water from an artificial seawater. These results indicate that solar desalination is realizable with the DR1 modified PTFE membrane by the direct irradiation of solar light to the membrane.