Mesoporous Silica from Water-Soluble Precursors in Hybrid Polysulfone Membranes: A Strategy for Enhanced Ciprofloxacin Removal under Low-Pressure Filtration

Abstract

The present study introduces high-performance mixed matrix membranes (MMM) designed to provide an improved balance in the permeability-selectivity trade-off for pharmaceutical remediation. By incorporating mesoporous silica (mSiO2) nanoparticles, synthesized via a water-soluble precursor route, into a polysulfone (PSf) matrix, a synergistic adsorptive-filtration platform was established for ciprofloxacin (CIP) remediation. The incorporation of mSiO2 nanoparticles influences the mass transfer rate between solvent and nonsolvent during the membrane production process and promotes modification in the asymmetric structure of the membrane, resulting in the formation of finger-like cavities and open terminal channels with reduced wall thickness. The mSiO2 incorporation promoted greater and interconnected porosity, in addition to greater hydrophilicity confirmed by the surface analysis. Results demonstrate a transition from ultrafiltration-like (UF-like) to nanofiltration-like (NF-like) behavior with increasing PSf concentration. For membranes cast from the 15 wt % PSf solution the addition of mSiO2 increased the flux and yielded a 4-fold increase in CIP removal capacity. For the PSf-20 series membrane, the incorporation of mSiO2 nanoparticles enhanced water flux while maintaining high CIP rejection (83.3 ± 13.4%). Notably, the PSf-18 series emerged as the optimized formulation, achieving a superior balance between high permeability and selectivity. This performance is driven by a synergistic mechanism: while the negative surface potential facilitates Donnan exclusion of zwitterionic CIP, the internal architecture enables convective-enhanced adsorption within the mSiO2 micro and mesopores. These findings highlight the potential of PSf/mSiO2 membranes as a low-pressure (2 bar), energy-efficient platform for advanced treatment of emerging micropollutants, providing a foundational step for future applications under more complex operating conditions.