Toward more sustainable-solvent-processed PVDF/carbon nanohorn membranes for efficient separation

Poly(vinylidene fluoride) (PVDF) membranes are indispensable for water treatment but suffer from intrinsic hydrophobicity-driven fouling and poor wettability. This study presents a catalyst-free, two-complementary membrane-functionalization strategy based on ammonia-plasma-treated carbon nanohorns (CNHs) and postgrafted sulfonic/zwitterionic groups to create durable, charge-tunable membrane interfaces. Membranes were fabricated using the sustainable solvent triethyl phosphate (TEP) via phase inversion. CNHs provide metal-free carbon scaffolding with superior biocompatibility compared to CNT/graphene alternatives, while post-grafted sulfonic groups enhance surface hydration and electrostatic repulsion of foulants. Comprehensive characterization (XPS, ATR-FTIR, Raman, TEM, contact angles, zeta potential) confirms successful covalent immobilization and synergistic surface chemistry. Membrane fouling experiments with humic acid (100 mg L􀀀 1, 6 h crossflow) reveal water permeability increases of + 33.0% (CNHs) and + 48.5% (sulfonated), reaching 2268 L m􀀀 2 h􀀀 1 bar􀀀 1, a 94% enhancement over pristine PVDF. Humic acid rejection reached ~85%, with flux recovery ratios of ~89% after simple cleaning, outperforming many reported benchmarks for CNT/GO-modified PVDF. Hansen Solubility Parameter modeling and predictive bioaccumulation screening (log BAF, BCF, Kow) suggest a comparatively low bioaccumulation potential for the selected modification agents and confirm reduced membrane– foulant affinity. This work establishes a practical pathway toward sustainable, high-flux, metal-free PVDF membranes for reliable water treatment, combining performance enhancement with environmental safety.