A general dopamine deposition strategy on polyether sulfone membrane for water purification

Abstract

As a biomass green material, polydopamine (PDA) shines in the field of water purification driven by solar energy with its strong adhesion and photoheating properties, but it is hard for PDA in tris solution to deposit on Polyether sulfone (PES) to obtain thick coating. To solve the problem, 3-aminopropyltriethoxysilane (AMEO) was chosen to modify PDA, and two-solvent strategy (alcohol/water) was applied. In this work, AMEO plays two roles: 1) catalyze the polymerization of dopamine (like tris solution); 2) improve the interaction between PDA and PES. In order to prove the universality of this strategy, the influence of the mixed ratio of three organic solvents (ethanol, methanol, isopropyl alcohol) and water on the deposition process was investigated. It was found that different alcohol/water mixed systems showed similar trends in polymerization rate and deposition amount. PES/PDA-AMEO (100 μL) with ethanol/water mixed ratio of 7:3 could achieve large deposition amount and relatively uniform surface. Under one sun irradiation (1 kWm−2), the water evaporation rate of the optimal PES/PDA-AMEO can reach 1.57 kgm−2h−1. Even for high concentration saltine water, the water evaporation rate is up to 1.05 kgm−2h−1. In addition, PES/PDA-AMEO obtained by this strategy can effectively intercept seawater salt and heavy metal ions, and the content of the distilled components meet the standards of potable water. Notably, this deposition strategy is expected to assist the uniform deposition of nanoparticles on PES to achieve the functionalization of the coating.