Performance of carbon adsorbent derived from cathodic waste in removal of petroleum hydrocarbons from aqueous environment

Cathode carbon is a hazardous byproduct generated during aluminium electrolysis. Converting this waste into an adsorbent offers an effective method for reducing sludge volume and improving waste management. In this study, cathode waste was dissolved in sodium hydroxide and heated to 90°C under magnetic stirring. After filtration, the remaining solids were treated with a mixture of water and sulfuric acid, stirred again, filtered, and washed with distilled water until the filtrate reached neutral pH. The morphology and chemical composition of the produced adsorbent were characterized using SEM, XRD, and XRF. Adsorption experiments determined that the optimal adsorbent doses for benzene, toluene, and para-xylene were 0.8, 0.6, and 0.2 g/L, respectively. The adsorbent showed capacities of 12.043 mg/g for benzene, 8.48 mg/g for toluene, and 10.775 mg/g for para-xylene, with removal efficiencies of 77%, 97%, and 86%. The fitting results indicated that adsorption of benzene and toluene followed the Langmuir model, while para-xylene was better described by the Freundlich model. The findings demonstrate that cathodic-waste–derived carbon adsorbent is highly effective for removing petroleum hydrocarbons from contaminated water and offers strong potential for water and wastewater treatment applications.