Simultaneous adsorption and detection of naphthenic acids using potassium-doped carbon dots/lignin-based porous...

Naphthenic acids (NAs) in petroleum wastewater are difficult to volatilize, degrade and persistent. In this study, we developed a potassium-doped carbon dots/lignin-based porous carbon composite (K-CDs/LPC-X) using renewable lignin as a carbon source and potassium-doped carbon dots (K-CDs) as a fluorescent probe. Lignin, a natural and sustainable biomass material, serves as a cost-effective, eco-friendly carbon precursor and forms highly porous structures during pyrolysis‌. The porous carbon effectively disperses K-CDs to prevent agglomeration while ensuring potassium fully contacts the pore structure, enhancing activation efficiency for synergistic NAs adsorption and detection. K-CDs/LPC-53 exhibits a BET surface area of 270 m²/g, abundant pores, and enriched oxygen-containing groups, significantly boosting adsorption performance. The maximum NAs adsorption was 56.285 mg/g, reaching equilibrium in 40 min, following the pseudo - second - order kinetic model and Freundlich isothermal adsorption models. The composite had a 2.5-15 mmol/L detection range and 2.326 mmol/L detection limit for NAs, showing a good linear relationship. Therefore, this study presents a new method for the preparation of lignin-based porous carbon by introducing nanomaterials for simultaneous adsorption and real-time detection. The proposed method offers significant advantages and broad application prospects for wastewater treatment applications.