Architected Composite Reverse Osmosis Membrane with Multibarrier for Enhanced Ammonium Selectivity.

Area of Science:

• Materials Science
• Environmental Engineering
• Chemical Engineering

Background:

• Conventional reverse osmosis (RO) membranes exhibit limited ammonium (NH₄⁺-N) rejection (∼93%) in wastewater treatment.
• Effective ammonium removal is crucial for water recycling and meeting sustainable development goals.

Purpose of the Study:

• To develop a novel thin-film composite RO (TFC-RO) membrane with enhanced ammonium rejection capabilities.
• To investigate the mechanism behind the improved ammonium rejection by functionalized membranes.

Main Methods:

• Fabrication of a TFC-RO membrane by doping polyamidoamine (PAMAM) dendrimers into the polyamide (PA) layer.
• Characterization of membrane structure, surface charge, and free-volume properties.
• Evaluation of ammonium rejection and water permeability through membrane performance testing.

Main Results:

• The PAMAM-doped TFC-RO membrane achieved an exceptional NH₄⁺-N rejection of 98.39%, surpassing conventional membranes.
• PAMAM dendrimers optimized interfacial polymerization, creating a defect-reduced PA layer with improved size-sieving and maintained water permeability (3.74 L/m²·h·bar).
• A synergistic 'structure-charge-concentration' mechanism involving protonated amine groups and molecular mimicry was identified for effective NH₄⁺ inhibition.

Conclusions:

• The filling-integrated TFC-RO membrane design offers a highly effective solution for ammonium removal in wastewater.
• This advanced membrane technology contributes to efficient low-carbon water recycling and sustainable water management.
• The study presents a promising approach for developing next-generation membranes for challenging water treatment applications.