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Polyelectrolyte-Based Sacrificial Protective Layer for Fouling Control in Reverse Osmosis Desalination
- Son, Moon, Yang, Wulin, Bucs, Szilard S., Nava-Ocampo, Maria F., Vrouwenvelder, Johannes S., Logan, Bruce E.
- Environmental science & technology letters 2018 v.5 no.9 pp. 584-590
- alginates, brackish water, brine solutions, coatings, desalination, electrolytes, filtration, fouling, models, reverse osmosis, sodium chloride
- Reverse osmosis (RO) membranes inevitably foul because of the accumulation of material on the membrane surface. Instead of trying to reduce membrane fouling by chemically modifying the membrane, we took a different approach based on adding a sacrificial coating of two polyelectrolytes to the membrane. After membrane fouling, this coating was removed by flushing with a highly saline brine solution, and a new coating was regenerated in situ to provide a fresh protective layer (PL) on the membrane surface. The utility of this approach was demonstrated by conducting four consecutive dead-end filtration experiments using a model foulant (alginate, 200 ppm) in a synthetic brackish water (2000 ppm of NaCl). Brine removal and regeneration of the PL coating restored the water flux to an average of 97 ± 3% of its initial flux, compared to only 83 ± 3% for the pristine membrane. The average water flux for the PL-coated membranes was 15.5 ± 0.6 L m–² h–¹ until the flux was decreased by 10% versus its initial flux, compared to 13.4 ± 0.5 L m–² h–¹ for the nontreated control. The use of a sacrificial PL coating could therefore provide a more sustainable approach for addressing RO membrane fouling.