Anchoring nano-zeolite NaX particles on polydopamine-modified PVDF/PAN electrospun membranes for enhancing interception, adsorption and antifouling performance

In this study, hydrophilic nano-zeolite NaX particles were successfully grafted onto poly(vinylidene fluoride)/polyacrylonitrile (PVDF/PAN) membrane through PDA (polydopamine) blending and coating techniques. The preparation parameters of PDA-blended or coated membranes on the chemical oxygen demand (COD) removal efficiency and solution flux were systematically investigated. Subsequently, the “bio-glue” of PDA made the nano-zeolite NaX particles anchor successfully onto its modified PVDF/PAN membranes through two methods. The selected M2' membrane, obtained via in situ nano-zeolite NaX loading, exhibited exceptional bovine serum albumin (BSA) concentration efficiency (93.75%), outstanding NH4+ removal efficiency (98%), high flux (198 L/(m2∙h)), and remarkable hydrophilicity due to the synergistic effect of PDA and nano-zeolite. The adsorption kinetics of NH4+ on all nano-zeolite NaX-modified membranes fitted well with the Avrami fractional-order (AFO) model. After modification by PDA and nano-zeolite NaX, M2 and M2' showed excellent antifouling performance because of the enhanced hydrophilicity, and the forceful electrostatic repulsion with BSA contaminant. Compared to M2, M2' displayed more stable and efficient filtration performance even after multiple cycles of simple regeneration. This study provides a practical and viable approach for the implementation of environmentally friendly adsorption/separation membranes in organic carbon interception and ammonium recovery.