Grape seeds waste activated carbon as an adsorber of paracetamol drug residue: Experimental and theoretical approaches.

• Grape seeds waste biochar activated with H 3 PO 4 develops a specific area over 500 m2/g. • The biochar's adsorption capacity of paracetamol drug residue from water exceeds 17 mg/g. • DFT elucidates the interaction mechanism between the drug residue and the biochar. • DLPNO/CCSD reveal strong interactions between P biochar groups and drug acetamide. • Thermodynamics analysis shows an endothermic, spontaneous drug residue physisorption. Activated carbon (AC) derived from grape seeds wastes and chemically activated with phosphoric acid was employed to remove paracetamol (PCT); from an aqueous solution; as a pharmaceutical compound model. The AC was characterized using several techniques, and a series of batch adsorption experiments were conducted. Additionally, a theoretical study investigated the interactions of PCT with various functional groups present on the AC surface. The results demonstrated that the developed AC possessed a well-developed pore structure and a high specific surface area (S BET = 543 m2/g). The AC also exhibited an acidic surface and a low pH pzc (2.5). Adsorption experiments revealed that the pseudo-second-order (PSO) and Freundlich models provided the best fits for experimental kinetic and equilibrium data, respectively. The maximum adsorption capacity of AC for PCT was found to be 17.3 mg/g. Thermodynamic analysis suggested endothermic, favorable, and spontaneous adsorption; with low enthalpy values (ΔH° = 8.099 kJ/mol), supporting physisorption. The DLPNO-CCDT(T)/6-311G(d,p) calculation method yielded the most reliable adsorption energy (E ads) and Gibbs free energy (Δ G ads) values between PCT and functional groups on the carbon surface, indicating strong interactions between the acid phosphate group of AC and the acetamide fragment of PCT (Δ G ads = −7.60 kcal/mol), and strong interactions between the ketone groups and lactone cycles with the hydroxyl (ΔG ads = −3.40 kcal/mol), and acetamide (ΔG ads = −1.91 kcal/mol) groups of PCT, respectively. The obtained results indicated, first, that the use of activated carbon from waste is an effective alternative adsorbent for the treatment of wastewater containing pharmaceutical compounds. Second, the application of theoretical computational methods in quantum chemistry provides a thorough understanding of the mechanism of the absorption of PCT at the carbon surface. [ABSTRACT FROM AUTHOR]