What question did this study set out to answer?

This research aims to explore the adsorption mechanisms of acetaminophen on CuO and ZnO nanoparticles using advanced computational methods.

March 30, 2026Open Access

Acetaminophen adsorption mechanism on CuO and ZnO nanoparticles: DFT and MD insights for wastewater treatment

Key Points

This research aims to explore the adsorption mechanisms of acetaminophen on CuO and ZnO nanoparticles using advanced computational methods.
Utilized density functional theory (DFT) to analyze electronic properties of adsorption complexes.
Conducted molecular dynamics (MD) simulations to assess binding energies and stability of acetaminophen on nanoparticles.
Evaluated energy decomposition to understand stabilization contributions in adsorption processes.
Examined RDFs and non-bonded interactions to characterize binding nature between nanoparticles and acetaminophen.
CuO shows stronger adsorption with binding energies of −276 to −277.6 kcal/mol compared to ZnO's −219 to −230 kcal/mol.
Electronic properties indicate CuO as a more effective electron acceptor than ZnO during adsorption.
Charge transfer evidence supports stronger chemisorption on CuO, while ZnO exhibits physisorption tendencies.
RDFs reveal shorter, more direct interactions on CuO, contrasting with longer-range bonding in ZnO.

Abstract

An integrated computational study combining density functional theory and molecular dynamics simulation were performed to elucidate the adsorption mechanism of acetaminophen on Copper Oxide (CuO) and Zinc Oxide (ZnO) nanoparticles in aqueous media. The global electronic descriptors of the optimized adsorption complexes show clear differences. CuO/acetaminophen exhibits E HOMO = −7.33, E LUMO = −6.87 (ΔEgap = 0.461 eV), low chemical hardness (η = 0.23), high softness (S = 4.33) and very large electrophilicity (ω = 109.35). In contrast, ZnO/acetaminophen has E HOMO = −5.76, E LUMO = −0.92 (ΔE gap = 4.84 eV), η = 2.42, S = 0.41 and ω = 2.30, indicating CuO as a much stronger electron acceptor. Fukui and MEP maps identify the carbonyl (O11) and phenolic (O7) oxygens as primary donors (O11 f − = 0.1398, f + = 0.0866, f° = 0.2264). NBO analysis reveals larger donor → acceptor stabilization for CuO (E 2 = 37.7 kcal/mol) than ZnO (E 2 = 8.5 kcal/mol), consistent with significant LP(O/N) → metal charge-transfer on CuO. MD simulations corroborate stronger binding on CuO (E ads = −276 to −277.6 kcal/mol) than ZnO (−219 to −230 kcal/mol) over 290-318 K. Energy decomposition shows that (E deformation = −182 to −186 kcal/mol) dominates stabilization in both systems, while CuO displays a much larger E rigid (−93 to −95 kcal/mol) than ZnO (−36 to −45 kcal/mol). RDFs and non-bonded decomposition indicate short range, electrostatic coordination bonding on CuO (1.9–2.0 Å), and longer-range, dispersion H-bonding dominated contacts on ZnO (> 3.5 Å). These descriptors support a mechanism in which CuO favors charge transfer coordination (chemisorption), while ZnO favors relaxation assisted physisorption. This could guide the development of practical adsorbents for water treatment. CuO for strong sequestration and ZnO for reversible capture. • Mechanistic Contrast. • Electronic Structure Drivers. • Primary Adsorption Sites. • Stronger Binding to CuO. • Charge Transfer Evidence. • Practical Implications for Water Treatment.

Acetaminophen adsorption mechanism on CuO and ZnO nanoparticles: DFT and MD insights for wastewater treatment

Key Points

Abstract

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