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Application of activated carbon in the adsorption treatment of refinery wastewater: Coal-based columnar activated carbon is used for adsorbing oil from water in the adsorption treatment of refinery wastewater. This type of activated carbon has an extremely strong adsorption capacity, enabling the treatment of oily industrial wastewater so that the emission concentration can be reduced to 8 mg/L. In the adsorption treatment of refinery wastewater, the use of activated carbon for advanced treatment of such wastewater can effectively reduce its COD. It is capable of removing color, odor, organic substances, soluble solids, as well as certain heavy metal ions from the water, with the removal efficiency increasing as the retention time increases. The oily wastewater from refineries is first treated through oil separation, air flotation, and biological treatment, and then undergoes further treatment via sand filtration and filtration with coal-based granular activated carbon. The phenol content in the wastewater decreased from 0.1 mg/L (after biological treatment) to 0.005 mg/L, cyanide decreased from 0.19 mg/L to 0.048 mg/L, and COD decreased from 85 mg/L to 18 mg/L. In refinery wastewater, the substances adsorbed by activated carbon are mainly hydrocarbons, whereas in petrochemical plant wastewater, the types of adsorbed substances are diverse and more complex. The compounds contained in these effluents include ethanol, ether, butyraldehyde, benzene, etc. The general tendency of adsorption varies depending on the type of compound and its molecular weight, which in turn affects the adsorption capacity.