The growing presence of pharmaceutical contaminants in water presents a serious challenge to environmental safety and public health. Antibiotics are particularly difficult to remove because their small molecular sizes allow them to pass through conventional treatment barriers, potentially contributing to the spread of antibiotic resistance. Although reverse osmosis (RO) membranes offer highly effective molecular separation, their long-term performance is often limited by material degradation under continuous aqueous operation. Researchers from City University of Hong Kong, together with collaborators from other leading institutions, have developed a functionalized titanium disulfide (TiS 2 ) membrane that combines efficient antibiotic rejection with improved resistance to water-induced degradation, providing a promising approach for advanced water purification.
Why This Membrane Matters
Two-dimensional transition metal dichalcogenide membranes offer precisely defined nanoscale channels that can selectively separate molecules according to their size. However, conventional transition metal sulfides can be vulnerable to oxidation and structural deterioration in water, limiting their practical application. The research team selected 1T-phase TiS 2 , which provides a stable layered structure, and addressed its intrinsic water sensitivity through surface functionalization. Importantly, the researchers identified water-initiated hydrolysis, rather than direct oxidation by molecular oxygen, as the dominant degradation pathway of pristine TiS 2 . This finding provides a clear direction for improving the durability of sulfide-based separation membranes.
Innovative Design and Mechanism
The team developed a straightforward electrostatic self-assembly strategy using three quaternary ammonium molecules: DTAB, DDAB, and TDAB. Their positively charged ammonium groups attach to negatively charged TiS 2 nanosheets, while their hydrophobic alkyl chains form protective barriers against direct water contact. At the same time, these molecules expand the interlayer spacing and regulate the effective widths of the membrane’s molecular transport channels. Density functional theory and molecular dynamics simulations further reveal that surface functionalization weakens water–TiS 2 interactions and reduces water adsorption, helping suppress hydrolysis and preserve the layered structure. Among the three modifiers, DDAB provides the most favorable balance between hydrophobic protection and molecular sieving.
Outstanding Performance
The optimized DD-TiS₂ membrane achieves antibiotic rejection rates of 96.3% for sulfamethoxazole, 92.4% for ciprofloxacin, 95.1% for tetracycline, and 96.9% for rifampicin. It also maintains stable separation performance over 30 filtration cycles and 15 days of continuous operation. Meanwhile, the functionalized membranes demonstrate water permeance reaching 46.8 L m -2 h -1 bar -1 . The DD-TiS₂ membrane additionally retains strong rejection performance in mixed-antibiotic solutions containing different salt concentrations, highlighting its potential under more complex water-treatment conditions.
Applications and Future Outlook
By integrating adjustable molecular sieving channels with effective antioxidation passivation, this work establishes a promising design strategy for durable two-dimensional membranes. The authors also demonstrate a scalable fabrication concept based on electrochemical exfoliation and vacuum filtration, with an estimated exfoliation energy consumption of only 0.72 kWh kg -1 . Additional cross-flow filtration tests further support the potential of these membranes for practical separation processes. Although further evaluation under real wastewater conditions is needed, this approach offers new opportunities for removing emerging pharmaceutical pollutants and developing more reliable membrane technologies for sustainable water treatment.
Nano-Micro Letters
News article
Enhanced Antibiotics Sieving by Exfoliated TiS2 Membranes via Surface Functionalization and Passivation
14-Aug-2026