Composition-dependent pore structure and filtration performance of hydrogel-filled membranes

Microfiltration (MF) membranes reject large-sized solutes (>0.1 μm) from feed streams. Filling up the MF pore space with porous polymers tailor solute rejection by virtue of membrane structure alterations. In this work, we synthesized poly(methacrylic acid-glycidyl methacrylate) (p(MAA-GMA)) hydrogels in polyethersulfone (PES) MF membrane pores and evaluated the role of hydrophobic GMA in membranes' structure, water transport, and performance under saline, oily, and real wastewater feed. Varying GMA concentration in hydrogel increased mesh size, thereby increasing membranes' permeability by 30 times compared to the p(MAA)-filled membrane. We quantified gel permeabilities using Happel's permeability model. Results indicated that hydrogels made from 0.05 M GMA contributed 22% to water transport, 15% more than p(MAA)-filled membrane. The membrane also showed hydrogel compaction effect during 24 h stability tests at 0.3 bar transmembrane pressure (TMP). Furthermore, we also found a drastic increase in permeate flux under CaCl₂ feed for GMA-containing membranes. All membranes showed salt retention at 5% permeate recovery, which formed the basis for estimating membranes' semi-permeability under each ion type using the Spiegler-Kedem-Katchalsky (SKK) model. When subjected to oily water feed, GMA containing membranes showed flux decline due to oil adsorption. However, none of the membranes did not show oil permeation. Textile wastewater filtration using PMG 5.0 showed COD reduction of 68% for high COD effluent, whereas, TDS reduced to 10% at 10% recovery with gradual flux increase under high-salinity effluent. Therefore, tailoring hydrogel compositions in MF membrane pores can potentially drive the applicability for industrial separations in upstream and downstream processes.