Copper oxide modified activated carbon for enhanced adsorption performance of siloxane: An experimental and DFT study

• Coper oxide could enhance the adsorption of siloxanes on activated carbons. • The adsorption mechanism and interaction between siloxane and CuO/AC are clarified by experiments and DFT calculations. • Siloxane adsorbs on the naked AC surface only by van der Waals forces. • Phenolic hydroxyl groups on the surface of activated carbons cause elongation of the Si O Si bonds in siloxanes. • Siloxanes are adsorbed on the CuO surface via C H---Cu Hydrogen bonds. CuO is successfully introduced into activated carbon (AC) by a simple impregnation method to improve the adsorption performance of AC on Octamethylcyclotetrasiloxane (D4), and the adsorption mechanism is investigated by combining adsorption experiments and theoretical calculations. Adsorption experiments demonstrate that introducing CuO could significantly enhance the adsorption performance of AC on D4. 10-CuO/AC-800 has the best adsorption performance (495 mg g −1 ). The density functional theory (DFT) calculations indicate that the adsorption energy of the D4 siloxane molecule on the CuO surface is about −1.40 eV, which is larger than other adsorption sites such as bare AC surface and AC with phenolic hydroxyl groups (AC-OH). In addition, more charge transfer occurs during the adsorption of D4 on the CuO surface, which greatly facilitates the formation of bonds. IGMH analysis proved that D4 siloxane is adsorbed on the CuO surface through C H---Cu hydrogen bond, which is much stronger than the interaction with the bare AC and AC-OH, thus significantly enhancing the adsorption capacity. The present work successfully applies CuO/AC to the adsorption of D4 siloxane, providing a new perspective for improving the treatment of siloxanes by AC.