Activated carbon characteristics and interaction mechanisms affect organic micropollutant removal from secondary...

Powdered activated carbon (PAC)-based technology, including stand-alone adsorption and combined with ozone (O₃), is being increasingly used to remove organic micropollutants (μP) from secondary effluent at full scale. However, the factors affecting PAC's standalone adsorption and catalytic ozonation capacities remain largely unknown when selecting the most suited PAC in practical applications. This study evaluates eight representative PACs with different structural and physicochemical properties for removing six representative μP from secondary effluent. Quantitative methods, i.e. morphological, textural and chemical characterizations, density functional theory calculations and correlation heatmaps, were systematically employed to identify the most relevant PAC-related factors. In the standalone PAC adsorption system, its fast adsorption capacity (within 30 min) for μP in real wastewater is significantly positively correlated with mesopore volume and specific surface area, due to the direct competition and pore-blocking effects of effluent organic matter (EfOM), while UVA₂₅₄ reduction also serves as a reliable predictor. When combined in one reactor, in contrast to findings in deionized water, catalytic ozonation exhibits negligible enhancement in real wastewater across the eight PACs, as evidenced by minimal changes in O₃ mass transfer and hydroxyl radical generation, despite variations in their base-functional group content (0.50-6.39 mmol/g). This is due to EfOM shielding and competition effects, as well as electrostatic repulsion and gas-solid-liquid mass transfer limitations hindering direct O₃-PAC interactions. This work informs the production and selection of suitable PACs and provides in-depth insights into optimizing O₃-PAC integration for μP removal from secondary effluent.