Efficient removal of organic pollutants in reverse osmosis concentrate by coupling granular activated carbon adsorption with ozone

Abstract

The advanced removal of organic pollutants from reverse osmosis concentrate (ROC) remained challenging due to the limitations of cost-efficiency in conventional treatment processes. This study proposed a novel integrated approach combining granular activated carbon (GAC) adsorption with ozone regeneration (GAC/O₃) for effective ROC remediation. The process involved two sequential stages: (1) adsorption of organic pollutants onto GAC until saturation, followed by (2) ozone-induced degradation of the adsorbed contaminants through in-situ regeneration. Continuous-flow experiments demonstrated that the hybrid GAC/O₃ system achieved a 63.6 % reduction in dissolved organic carbon (DOC) concentration (from 44.18 mg/L to 16.09 mg/L) over five consecutive cycles, with ozone consumption significantly reduced by 10.9-fold (4.9 mg O₃/mg DOC) compared to standalone ozonation. Mechanistic analyses revealed that organic pollutant adsorption was dominated by π–π interactions between aromatic moieties and pore-filling effects. The oxygen-containing groups on the surface of GAC, phenolic hydroxyl and carboxyl group, were used to active O₃ to form hydroxyl radical for the adsorbed organic pollutants destroyed. This work provided a theoretical foundation for the GAC/O₃ system as a sustainable strategy to enhance ROC treatment efficiency.