Membrane Recycling: Exploring Ozone as a Viable Alternative to Chlorine for Polymeric Membrane Transformation

Area of Science:

• Materials Science
• Environmental Chemistry
• Chemical Engineering

Background:

• Ozone is a potent oxidant used for material degradation and polymer modification.
• Chlorine oxidation is a conventional method for membrane conversion, but it is time-consuming and requires high doses.
• End-of-life reverse osmosis (RO) membranes present a recycling challenge.

Purpose of the Study:

• To evaluate ozone as a sustainable alternative to chlorine for converting end-of-life RO and nanofiltration (NF) membranes.
• To characterize the performance of ozone-treated membranes in terms of permeability and salt rejection.
• To compare the efficiency of ozone oxidation with chlorine oxidation for membrane transformation.

Main Methods:

• Membrane samples (RO and NF) were exposed to ozone at high (20 ppm) and low (3 ppm) concentrations.
• Permeability, salt rejection, and surface characteristics of treated membranes were analyzed.
• Ozone treatment duration and dosage were varied to assess degradation patterns.

Main Results:

• Low ozone exposure (3 ppm) selectively degraded the polyamide layer, transforming RO membranes into NF-like membranes.
• Ozone treatment achieved comparable performance to chlorine oxidation in significantly less time and at lower doses.
• High ozone exposure (20 ppm) degraded both polyamide and polysulfone layers, indicating potential for polyester backing layer recycling.
• Ozone-induced degradation was patchy due to bubble interactions, contrasting with the uniform attack by chlorine.

Conclusions:

• Ozone is a viable and more sustainable alternative to chlorine for transforming polymeric membranes.
• Ozone oxidation offers a faster and more efficient method for membrane recycling and repurposing.
• The study opens possibilities for advanced recycling of membrane components through controlled ozone degradation.