Investigation of performance and antifouling mechanisms of calcium borate-modified PVDF membranes: Insights from the dual-mechanism fouling model and XDLVO theory

Membrane modification and the development of advanced materials represent promising strategies to mitigate membrane fouling and improve separation performance. In this study, a novel calcium borate nanoparticle (CaB NPs) with a tetrahedral structure was employed to modify polyvinylidene fluoride (PVDF) membranes through a synergistic surface engineering approach. The modified membranes were systematically evaluated in terms of permeability, fouling resistance, and antifouling mechanisms. At the optimal CaB NPs dosage of 15 mg (corresponding to a membrane area of 78.5 cm 2 ), the pure water flux increased by 3.59-fold, and the water contact angle was reduced from 74.9° (pristine) to 39.4°, while the zeta potential decreased from 38.4 mV to 29.8 mV. Additionally, the rejection of protein foulants improved by 20–30 % compared to that of the pristine membrane. The structural rearrangement of CaB NPs under alkaline conditions enhanced surface hydrophilicity and charge properties. Dual-mechanism fouling model analysis revealed that membrane fouling shifted from predominantly irreversible to reversible after modification, enabling effective foulant removal through physical cleaning. Furthermore, extended Derjaguin–Landau–Verwey–Overbeek (XDLVO) theory indicated that the CaB-modified membrane exhibited a markedly higher energy barrier toward bovine serum albumin (BSA) adsorption. This study offers the mechanistic insights into protein fouling mitigation, and highlights its potential in sustainable wastewater treatment.