Poly(aryl cyanurate)-Based Thin-Film Composite Nanofiltration Membranes

Area of Science:

• Materials Science
• Chemical Engineering
• Polymer Chemistry

Background:

• Polyamide nanofiltration membranes are widely used but suffer from limited stability due to hydrolysis-susceptible amide bonds.
• Developing alternative membrane materials with enhanced stability is crucial for advanced separation processes.

Purpose of the Study:

• To synthesize and characterize novel poly(aryl cyanurate) nanofiltration membranes using interfacial polymerization.
• To evaluate the performance and stability of these new membranes compared to conventional polyamide membranes.

Main Methods:

• Interfacial polymerization of cyanuric chloride and 1,1,1-tris(4-hydroxyphenyl)ethane (TPE) on a polyethersulfone support.
• Characterization of membrane performance including molecular weight cutoff, permeance, and salt retention.
• Assessment of membrane stability under various acidic and alkaline pH conditions.

Main Results:

• Successfully synthesized poly(aryl cyanurate) membranes with a molecular weight cutoff of 400 g/mol and high retention for divalent ions (Na2SO4: 97.1%, MgSO4: 92.8%).
• Membranes exhibit a negative surface charge, indicated by preferential retention of divalent cations over anions.
• Despite the absence of amide bonds, membranes showed performance decline under extreme pH (1 and 13) and moderate alkaline conditions (pH 12) due to aryl cyanurate bond hydrolysis.

Conclusions:

• Poly(aryl cyanurate) membranes present a promising alternative to polyamide membranes, offering good initial nanofiltration performance.
• The aryl cyanurate linkage, while avoiding amide hydrolysis, is susceptible to degradation under harsh pH conditions, limiting long-term operational stability.
• Further research is needed to improve the pH stability of poly(aryl cyanurate) membranes for broader applications.