Reverse osmosis membrane composition, structure and performance modification by bisulphite, iron(III), bromide and...

Area of Science:

• Water treatment technologies
• Membrane science and engineering
• Environmental chemistry

Background:

• Reverse osmosis (RO) membranes are crucial for water purification.
• Understanding membrane degradation from common water contaminants is vital for effective water treatment.
• Bisulphite, chlorite, bromide, and iron(III) are potential RO membrane foulants.

Purpose of the Study:

• To investigate the impact of bisulphite, chlorite, bromide, and iron(III) on RO membrane properties.
• To elucidate the mechanisms of membrane damage and performance alteration.
• To correlate structural changes with observed transport properties.

Main Methods:

• Membrane composition analysis using Rutherford backscattering spectrometry (RBS).
• Performance assessment via water and chloride permeation.
• Application of a modified solution-diffusion model.
• Analysis of membrane structure, including pore size and polyamide layer aggregation.

Main Results:

• Iron(III) in the presence of bisulphite caused rapid membrane damage via bisulphite autooxidation and radical generation.
• Chloride passage significantly increased (5.3-5.1 fold), indicating compromised membrane integrity.
• No major changes in water permeability or overall membrane composition were detected.
• Structural analysis revealed increased pore network size and aggregate pores in the polyamide layer, without amide bond cleavage.

Conclusions:

• The combination of iron(III) and bisulphite poses a significant threat to RO membrane performance.
• Observed transport property changes are directly linked to identified structural alterations in the polyamide layer.
• RO membrane integrity can be compromised by specific chemical interactions, impacting water purification efficiency.