Recyclable graphene oxide nanoadsorbents for the removal of hormone-disrupting pollutants: a DFT investigation of BPA and atrazine.

CONTEXT: Endocrine-disrupting chemicals (EDCs) such as bisphenol A (BPA) and atrazine (ATR) are persistent organic pollutants that pose severe environmental and health risks even at ultra-trace concentrations. Although graphene oxide (GO)-based nanoadsorbents exhibit high adsorption capability toward organic contaminants, the balance between adsorption strength and adsorbent regenerability remains poorly understood at the molecular level. In this work, a comprehensive multiscale computational investigation was conducted to elucidate the adsorption, electronic interaction, thermal stability, and desorption kinetics of BPA and ATR on functionalized graphene oxide surfaces containing hydroxyl (GO-OH), amino (GO-NH₂), and carboxyl (GO-COOH) groups. The results demonstrate that GO-COOH exhibits the strongest adsorption behavior, characterized by the smallest HOMO-LUMO energy gap (ΔE = 0.052 eV), the highest charge-transfer intensity (~0.142 e), and the strongest noncovalent stabilization dominated by hydrogen bonding and interfacial polarization. In contrast, GO-OH displays a more balanced adsorption-desorption profile with the lowest desorption activation barrier (96.48 kcal·mol-1), compared with GO-NH₂ (100.63 kcal·mol-1) and GO-COOH (179.96 kcal·mol-1), indicating superior regenerability and recyclability. Molecular dynamics (MD) simulations further confirm the structural stability of all adsorption complexes under NVE conditions. Overall, the combined DFT-MD-IRC framework reveals that surface functionalization critically governs the trade-off between adsorption efficiency and desorption feasibility, identifying hydroxyl-functionalized GO as a promising recyclable nanoadsorbent for efficient EDC remediation.

METHODS: Initial adsorption configurations were generated using the Adsorption Locator module in Materials Studio with the COMPASSIII force field and simulated annealing Monte Carlo sampling. The most stable adsorption geometries were optimized using density functional theory (DFT) calculations at the B3LYP/6-31G (d, p) level implemented in Gaussian 16 with implicit solvation effects. Electronic properties, charge-transfer behavior, and frontier molecular orbitals (FMO) were analyzed through DFT-based descriptors, while noncovalent interactions (NCI) were characterized using QTAIM and NCI analyses implemented in Multiwfn. Molecular dynamics simulations were performed using the Forcite module under the NVE ensemble to evaluate thermal stability and structural persistence. Transition-state (TS) searches and intrinsic reaction coordinate (IRC) calculations were subsequently conducted to quantify the activation energies associated with pollutant desorption from the functionalized GO surfaces.