Nanofiltration Membranes Containing a Metal-Polyphenol Network Layer: Using Casting Solution pH as a Tool to Tailor...

Area of Science:

• Materials Science
• Chemical Engineering
• Separation Science

Background:

• Thin-film composite (TFC) membranes are crucial for separation processes.
• Metal-polyphenol networks (MPNs) offer tunable properties for membrane applications.
• Controlling membrane characteristics through fabrication parameters is essential for optimizing performance.

Purpose of the Study:

• To fabricate TFC membranes with MPN selective layers using supramolecular self-assembly.
• To investigate the effect of pH on membrane characteristics, including porosity, contact angle, and separation performance.
• To evaluate the separation selectivity and antifouling properties of the developed MPN membranes.

Main Methods:

• Fabrication of TFC membranes via layer-by-layer deposition of tannic acid (TA) and ferric ion (Fe3+).
• Tuning membrane properties by adjusting the pH of the TA casting solution (pH 3 to 8.5).
• Characterization of membrane surface properties (porosity, contact angle) and evaluation of separation performance (water permeance, dye retention) and antifouling behavior.

Main Results:

• Increasing pH from 3 to 8.5 decreased surface porosity and water contact angle, tuning water permeance.
• High retention of anionic dyes (naphthol green B, orange II) and low retention of neutral dyes (riboflavin) were achieved.
• Demonstrated a 30.8-fold higher permeation of neutral dye over anionic dye, indicating significant selectivity.
• MPN layers exhibited robust stability and an 82% flux recovery ratio in fouling tests.

Conclusions:

• pH-controlled supramolecular self-assembly is an effective strategy for fabricating high-performance TFC membranes.
• The developed MPN membranes show excellent selectivity for separating anionic from neutral molecules.
• These membranes possess robust antifouling properties, making them promising for advanced separation applications.