Adsorption of the dinotefuran enantiomers by Mg-modified peanut shell biochar: mechanism, site identification, and density functional theory validation.

BACKGROUND: The chiral pesticide dinotefuran, a neonicotinoid insecticide with high water solubility and persistence, poses significant ecological systems risks by interfering with the structure and functions of aquatic ecosystems and accumulating progressively through the food chain. Mg-modified biochar derived from peanut shell (MPB) and corn stalk, along with pristine peanut shell and corn stalk biochar, were prepared and characterized. The adsorption mechanisms of the two dinotefuran enantiomers (R-dinotefuran and S-dinotefuran) were investigated. RESULTS: Adsorption experiments demonstrated that MPB achieved the highest adsorption capacity for both enantiomers, with no significant difference between them. At 298.15 K, the maximum adsorption capacities of MPB for R-dinotefuran and S-dinotefuran were 78.62 and 75.39 mg g-1 respectively. All adsorption processes were spontaneous, exothermic, and associated with a decrease in disorder. Both dinotefuran enantiomers underwent removal by MPB through identical primary mechanisms, including hydrogen bonding, π-π interactions, electrostatic attraction, complexation, ligand exchange, and pore filling. Density functional theory calculations revealed minimal energy gaps between the Highest Occupied Molecular Orbital of MPB and the Lowest Unoccupied Molecular Orbital of both enantiomers (2.475 and 2.524 eV). These gaps are 3.3% to 40.1% lower than those for other biochars, further confirming the superior reactivity and adsorption performance of MPB, as well as the negligible enantioselectivity between the two enantiomers. CONCLUSION: MPB exhibits high adsorption performance for the chiral pesticide dinotefuran, demonstrating its potential to mitigate dinotefuran contamination in surface water and groundwater. These results offer valuable insights into the efficient and selective removal of chiral pesticides from aquatic environments. © 2026 Society of Chemical Industry.