From olive pomace waste to valuable resource: Investigating olive pomace activated carbon for removing organic dyes in water

To address the issues of high toxicity and significant environmental harm caused by dye wastewater, this study used olive pomace, a by-product of the olive oil industry, as a raw material to produce high-performance activated carbon (OP-AC) using a two-step pyrolysis method. This approach achieves the dual goals of “treating waste with waste” and resource utilisation. OP-AC exhibited excellent adsorption performance, with adsorption capacities for malachite green(MG), neutral red(NR), acid blue 113(AB113), and acid orange G(AOG) reaching as high as 1012.0, 825.5, 870.5, and 1365.5 mg·g −1 , respectively. The material is characterised by a high specific surface area (1678.49 m 2 ·g −1 ) and a hierarchical porous structure, providing abundant active sites for adsorption. The adsorption process was found to be in accordance with the pseudo-second-order kinetic model. The Langmuir model described the adsorption isotherms of cationic dyes, while the Freundlich model described anionic dyes better. The adsorption was identified as spontaneous and endothermic. Pore filling, hydrogen bonding, π-π interactions, and the electrostatic interaction were identified as the primary processes governing the interaction between dye particles and OP-AC. Notably, in actual water systems,the capacity for adsorption of MG (≥495.37 mg·g⁻¹), NR (≥492.83 mg·g⁻¹), and AOG (≥430.9 mg·g⁻¹) by OP-AC exceeded those observed in deionized water(MG:400.9 mg·g⁻¹, NR: 329.6 mg·g⁻¹, AOG:385.6 mg·g⁻¹). Furthermore, the OP-AC demonstrated robust adsorption efficacy following five successive adsorption-desorption cycles.This study provides a reliable pathway for the resource utilization of waste biomass to prepare highly efficient adsorbents, showcasing broad application prospects in the treatment of dye wastewater. • Hierarchical porous activated carbon was prepared from olive pomace. • Activated carbon had a high specific surface area (1678.49 m 2 /g). • Activated carbon showed high uptake for cationic, anionic, and mixed dye. • Activated carbon exhibits superior dye adsorption in actual water systems.