Optimizing polyamide thin-film composite desalination membranes: simple and performance-effective modification by...

Area of Science:

• Materials Science
• Chemical Engineering
• Environmental Science

Background:

• Polyamide (PA) thin-film composite membranes are crucial for water desalination.
• Improving membrane flux and selectivity remains a key challenge in reverse osmosis (RO).
• Incorporating zwitterionic groups can enhance membrane properties by altering surface hydrophilicity.

Purpose of the Study:

• To synthesize and incorporate a zwitterionic monohydroxyl monomer (ZHM) into PA active layers.
• To evaluate the impact of ZHM incorporation on membrane surface properties, flux, and salt rejection.
• To develop enhanced RO membranes with improved performance characteristics.

Main Methods:

• Interfacial polymerization using ZHM, m-phenylenediamine (MPD), and trimesoyl chloride (TMC).
• Surface characterization via water contact angle (WCA) and field emission scanning electron microscopy (FESEM).
• Spectroscopic confirmation using X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR).
• Performance testing using dead-end filtration of NaCl and MgSO4 solutions at 15 bar.

Main Results:

• Successful incorporation of ZHM into PA active layers confirmed by XPS and FTIR.
• ZHM-modified membranes exhibited significantly enhanced water flux compared to the control (ZHM-0).
• Flux increased from 6.8 to 9.1 L/m²h (NaCl) and 6.7 to 9.5 L/m²h (MgSO4).
• Salt rejection remained high, approximately 91% for NaCl and 100% for MgSO4, comparable to the control.

Conclusions:

• The synthesized ZHM effectively introduces zwitterionic sulfobetaine groups into PA membranes.
• Zwitterionic modification via ZHM enhances membrane flux without compromising salt rejection capabilities.
• This approach offers a promising strategy for developing high-performance RO membranes for water treatment.