Spray assembled, cross-linked polyelectrolyte multilayer membranes for salt removal

Area of Science:

• Materials Science
• Polymer Chemistry
• Separation Technology

Background:

• Polyelectrolyte multilayer membranes are crucial for separation processes.
• Cross-linking enhances membrane stability and performance.
• Click chemistry offers efficient and specific cross-linking methods.

Purpose of the Study:

• To synthesize spray-coated, cross-linked polyelectrolyte multilayer membranes.
• To investigate the effect of cross-linking on membrane structure and performance.
• To explore flux enhancement strategies without compromising ion rejection.

Main Methods:

• Synthesis of cross-linked polyelectrolyte multilayer membranes via spray coating.
• Modification of poly(acrylic acid) (PAA) and poly(allylamine) hydrochloride (PAH) with alkyne and azide groups.
• Alkyne-azide click chemistry for membrane cross-linking.
• Characterization of membrane structure, pore size, and ion rejection.

Main Results:

• Lower ionic strength deposition yielded smoother, denser membranes.
• Increased cross-linking reduced membrane pore size.
• Achieved up to 80% CaCl2 (divalent) and 50% NaCl (monovalent) rejection.
• Combining poly(sodium-4-styrenesulfonate) (PSS) with cross-linkable PAA increased flux without reducing ion rejection.

Conclusions:

• Click chemistry is effective for creating cross-linked polyelectrolyte membranes.
• Cross-linking degree is a key parameter for controlling membrane pore size and ion selectivity.
• Strategies exist to enhance membrane flux while maintaining high ion rejection.