Polyamide Membranes with Tunable Surface Charge Induced by Dipole-Dipole Interaction for Selective Ion Separation

Area of Science:

• Materials Science
• Chemical Engineering
• Environmental Science

Background:

• Nanofiltration (NF) membranes are crucial for precise ion separation, essential for resource recovery and a circular water economy.
• Current methods for fabricating selective NF membranes face significant technical challenges.
• Leveraging intermolecular forces like dipole-dipole interactions to tune membrane properties remains underexplored.

Purpose of the Study:

• To introduce a novel strategy for tuning the surface charge of polyamide NF membranes.
• To investigate the role of dipole-dipole interactions in modifying membrane structure and selectivity.
• To achieve efficient and selective ion separation using engineered NF membranes.

Main Methods:

• Interfacial polymerization of polyamide membranes using trimesoyl chloride (TMC).
• Introduction of polar solvents with large dipole moments during polymerization to induce dipole-dipole interactions.
• Characterization of membrane surface charge and chemical properties.
• Evaluation of membrane performance for selective cation and anion separation.

Main Results:

• A novel strategy successfully tuned the surface charge of polyamide membranes via solvent-induced dipole-dipole interactions.
• The dipole-dipole interaction modulated the amidation reaction, altering the density of surface carboxyl groups.
• Prepared positively charged ((PEI-TMC)-NH2) and negatively charged ((PEI-TMC)-COOH) membranes exhibited high water permeance.
• These membranes demonstrated highly selective separation of cations and anions, respectively.

Conclusions:

• Solvent-induced dipole-dipole interactions can effectively alter the charge type and density of polyamide membranes.
• This method provides a new pathway for fabricating tunable surface charge membranes for selective ion separation.
• The developed NF membranes offer a promising solution for efficient resource recovery and water purification applications.