In a groundbreaking study published in the journal *Desalination and Water Treatment* (translated as *Desalination and Water Purification*), researchers have explored a novel approach to repurpose end-of-life seawater reverse osmosis (SWRO) membranes for brine concentration, potentially offering significant energy savings and environmental benefits for the water and energy sectors. The research, led by Yusik Kim from the School of Civil and Environmental Engineering at Kookmin University in Seoul, South Korea, delves into the oxidative tuning of commercial SWRO membranes to achieve low-salt-rejection reverse osmosis (LSRRO) operation.
The study is motivated by the principles of the circular economy, aiming to extend the life and utility of SWRO membranes beyond their initial use. By oxidizing these membranes, the researchers found that they could significantly increase salt permeability while maintaining water permeance, creating a tunable low-rejection behavior suitable for brine concentration. “Oxidation increased water permeance modestly but increased salt permeability by orders of magnitude,” Kim explained, highlighting the transformative potential of this process.
The research team evaluated two oxidation protocols: static soaking and pressurized dead-end filtration oxidation. They discovered that filtration oxidation could elevate oxidant concentration at the membrane surface due to hypochlorite rejection and concentration polarization. However, they also noted that harsh oxidation and high-salinity operation could compromise the integrity of the porous support layer, leading to rate-limiting issues.
To translate these findings into practical applications, the researchers updated a system-scale LSRRO model to compute osmotic pressure using a non-ideal, water-activity formulation and to represent salinity-dependent effective salt transport. They compared specific energy consumption (SEC) under identical separation constraints and benchmarked the tuned-RO window against representative commercial nanofiltration (NF) membranes.
The implications of this research are far-reaching for the water and energy sectors. By repurposing end-of-life SWRO membranes for brine concentration, industries could achieve significant energy savings and reduce waste. “This study defines practical operating windows and key validation steps required for translating oxidative downcycling to real end-of-life elements,” Kim stated, emphasizing the need for further research and development.
As the world grapples with water scarcity and the need for sustainable energy solutions, this research offers a promising avenue for innovation. By leveraging the principles of the circular economy, industries can minimize waste and maximize resource efficiency, paving the way for a more sustainable future. The study published in *Desalination and Water Treatment* serves as a crucial stepping stone in this journey, offering valuable insights and practical guidelines for the oxidative tuning of SWRO membranes.