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RF-Sputtered ZnO Nano-Coatings on Polyamide Thin-Film Composite Membranes for Tuned Nanofiltration Selectivity
Catalina Vargas1, Daniel A Palacio2, Jesús Ramírez3
1Departmento de Ingeniería Química, Universidad de Concepción, Edmundo Larenas 219, Box 160-C, Concepción 4070409, Chile.
Nanomaterials (Basel, Switzerland)
|May 26, 2026
Summary
Researchers modified nanofiltration membranes (NF) with zinc oxide (ZnO) coatings to improve salt rejection. This surface modification enhanced selectivity but reduced water permeate flux, offering a tunable trade-off for water purification.
Area of Science:
- Materials Science
- Chemical Engineering
- Environmental Science
Background:
- Global water stress necessitates advanced desalination and purification technologies.
- Commercial nanofiltration (NF) membranes face permeability-selectivity trade-offs and limited surface tunability.
Purpose of the Study:
- To investigate the surface modification of NF90 membranes using ZnO coatings.
- To evaluate the impact of ZnO deposition on membrane surface properties, water flux, and NaCl rejection.
Main Methods:
- Surface modification of NF90 membranes via radio frequency (RF) sputtering of ZnO (30-120 s).
- Characterization using X-ray diffraction (XRD) and water contact angle measurements.
- Evaluation of hydraulic performance (permeate flux) and NaCl rejection under varying pressures.
Main Results:
- Successful deposition of crystalline Wurtzite ZnO with preferential (002) orientation.
- Significant increase in surface hydrophobicity (water contact angle up to 140.4°).
- Reduced water permeate flux (47-50% decrease) and enhanced NaCl rejection, particularly at lower pressures.
Conclusions:
- RF sputtering of ZnO is a viable post-fabrication method for tuning NF membrane selectivity.
- ZnO coating introduces a trade-off between improved salt rejection and reduced water permeate flux.
- The Spiegler-Kedem model effectively describes the observed rejection-flux behavior.
