Controlled aggregation of phytic acid metal complex on polysulfone ultrafiltration membrane toward simultaneous rejection of highly emulsified oils and dyes

Abstract

Despite enormous application prospect in wastewater treatment, the moderately hydrophilic ultrafiltration (UF) membrane with the intrinsic pore size has been proved ineffective for removal of highly emulsified oil droplets and organic dyes merely by the size screening effect. Although modification of polymer fibrous membranes by the phytic acid (PA)-metal complex coatings has been widely investigated for updating the membrane performances, the feasibility of this simple dip-coating approach in modifying polymer UF membrane with an asymmetric structure is still unrevealed and required testifying. Herein, we report the modification of asymmetric polysulfone (PSF) UF membranes through the formation of hydrophilic PA-FeIII complex coatings via controlled aggregation. We reveal that 1-cycle crosslinked PA-FeIII sequential assembly with adequate reaction time represents the optimal conditions for achieving PA-FeIII/PSF membranes with desired wettability, separation performances and reusability. The PA-FeIII complex aggregations afford the hierarchical roughness and the high density of phosphonic acid group, which favors the trapping of water and formation of a stable hydration layer to separate highly emulsified oil droplets and prevent them from fouling the membrane. Besides, the molecular layer deposition mode of the PA-FeIII compact film enables a fine adjustment of the pore aperture, guaranteeing the simultaneous rejections to small-sized emulsified droplets and non-specific organic dye molecules. The rapid, easy to scale up, and cost-effective modification process for polymer UF membranes is expected to be of technological significance for various practical applications, especially for sophisticated oily wastewater decontamination.