Efficient removal of benzotriazole in a bioretention column by porous carbonized wood from urban stormwater

Conventional bioretention systems exhibit limited efficacy in benzotriazole removal from stormwater runoff due to the compound’s high solubility and mobility. Here, this study investigated the efficient removal of benzotriazole from urban stormwater using porous carbonized wood (PCW) in bioretention columns. Derived from Basswood through CO₂ activation, PCW exhibited a high specific surface area (511 m²/g) and rapid adsorption equilibrium (5 h), with a maximum adsorption capacity of 175.12 mg/g for benzotriazole. Column experiments demonstrated that granular PCW (4 mm particle size) achieves > 95 % benzotriazole removal under varying hydraulic conditions (influent concentrations: 5–15 mg/L), while powdered PCW showed near-complete removal (∼100 %). However, granular PCW significantly enhanced hydraulic conductivity (52.5 mL/min vs. 5.5 mL/min for powdered PCW), effectively mitigating clogging risks. The CO₂ activation process enhanced mesopore formation and surface functionality, facilitating adsorption via hydrogen bonding and electrostatic interactions. Compared to conventional biochar and sand, PCW demonstrated superior selectivity and stability across pH (3–11) and coexisting ions. Granular PCW balanced high contaminant removal with optimal hydraulic performance, offering a sustainable solution for stormwater treatment. In the end, this work highlights the potential of granular PCW as a scalable, efficient amendment in bioretention systems to address persistent organic pollutants in urban runoff.