Computational study on thiolated and functionalized graphene oxide for heavy metal recovery

Abstract

The escalating use of heavy metals in industrial, agricultural, and medical applications has amplified pollution challenges, necessitating innovative remediation strategies. This study investigates the potential of a hybrid graphene oxide/thiolated-poly(N-isopropylacrylamide) (GO/GOSH@PNM) system for the reversible, temperature-dependent removal of heavy metals, specifically Pd(II), Pb(II), and Cd(II), from aqueous environments. Molecular dynamics (MD) simulations reveal that below the lower critical solution temperature (LCST) of 32 °C, the PNM polymer adopts a hydrophilic coil configuration, enabling efficient coordination of metal cations via hydroxyl, thiol, and amide oxygen functional groups. Density functional theory (DFT) calculations corroborate these findings, highlighting favorable adsorption free energies and strong interactions between the polymer and metal ions at lower temperatures. Above 32 °C, the polymer transitions to a hydrophobic globular conformation, reducing cation affinity and facilitating their release. This temperature-induced binding and release mechanism allows for heavy metal recovery and the regeneration of the hybrid system. The GO surface demonstrates higher polymer affinity than the GOSH surface, likely due to its increased hydroxyl group density. These findings underline the potential of the GO/GOSH@PNM system for sustainable and efficient heavy metal remediation, with further optimization promising enhanced performance.