Statistical physics modelling and density functional theory calculations for glyphosate adsorption using zinc oxide-doped activated carbon

Abstract

Glyphosate (GPS), an organophosphorus herbicide known for its genotoxic and carcinogenic effects, poses environmental and health risks. Addressing the need for sustainable removal methods, adsorption emerges as a promising, eco-friendly, and cost-effective approach. To enhance GPS removal, a bio-fabricated ZnONP-doped activated carbon (Zn@AC) was proposed and investigated for its adsorption mechanism. The adsorbent was created by pyrolyzing activated carbon derived from coconut fiber and introducing ZnO nanoparticles synthesized using Jatropha curcas leaf extract. Subsequently, the material underwent thorough characterization. The adsorption mechanism was explored using statistical physical modeling and Density Functional Theory (DFT) under different conditions: temperatures (303 K to 353 K), pH levels (4.5 to 6), and GPS concentrations (5 mg/L to 50 mg/L). The monolayer, double layer, and multilayer models were used to gain comprehensive insight into GPS removal performance, and the results showed that Zn@AC was superior to AC and ZnONP. The adsorption capacity for monolayer quantity for GPS-Zn@AC was found to be 511.49 mg/g, and the density of receptor sites for Zn@AC was observed to be 85.68 ± 1.71. These values were obtained using the M5 model, which is a statistical physical modeling approach. The study provides insights into the adsorption of GPS on modified materials and the use of advanced statistical physics models for interpretation. The temperature-dependent changes and energy profiles (∊1 > 10 kJ/mol > ∊2) confirmed that the reaction was endothermic and driven by electrostatic interference. The alignment of experimental and DFT highlighted Zn-O interactions, showing the hierarchy of GPS-Zn@AC complexes (IV > II > III > I > V). These findings offer valuable insights for engineering and material science.