Self-Cleaning Membranes for Water Purification by Codeposition of Photo-Mobile 4,4'-Azodianiline and Bio-Adhesive Polydopamine
Ramanan, Sankara Narayanan
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Stimuli-responsive membranes have been widely explored to mitigate fouling on the membrane surface to achieve stable performance of water purification. Herein, we demonstrate a facile one-step coating of photo-mobile materials on membrane surface to impart self-cleaning property upon exposure alternatively to ultraviolet (UV) and visible light. Specifically, we successfully co-deposited photo-mobile 4,4’-azodianiline (AZO) and a bio-adhesive polydopamine (PDA) on the surface of ultrafiltration (UF) membranes. The effect of the coating layer on the surface hydrophilicity and pure water permeance was systematically evaluated. The photoresponsive properties of AZO in solutions and thin films with PDA was characterized using UV-Vis absorption spectroscopy. When shed with UV light, AZO undergoes photoisomerization from trans- AZO to cis -AZO, increasing surface hydrophilicity and decreasing the volume, while the exposure to visible light enables the transition from the cis- to trans- configuration. The resulted self-cleaning behavior of the modified membranes is demonstrated in treating 1 g/L bovine serum albumin (BSA) solution. For example, the self-cleaning of UF membranes increased water flux by ~160% when the membranes were challenged with the BSA solution.