Onion skin-derived sorbent for the sequestration of methylparaben in contaminated aqueous medium

Carbon-based adsorbents were produced from onion skin waste for the adsorption of methylparaben from contaminated water. The biomass-derived carbon was characterized using various established analytical techniques. The microscopic examinations revealed micro- and mesoporous structures with a partially disordered network of the graphenic carbon-like multilayer structure, confirmed by XPS and Raman spectra. XRD analysis revealed that the biomass-derived carbon is largely amorphous with the graphitic phase also confirmed. Aside from the prominence of sp(2) hybridized carbon, FTIR analysis shows the existence of moieties and functional groups that may facilitate the sorption of methylparaben or other organic pollutants if explored. The adsorption isotherm revealed that the multilayer adsorption model (Freundlich) best fits experimental data with an SSE value of 0.454. A complex adsorption process is suspected between methylparaben and OSDC, and the physicochemical properties of the sorbate and sorbent played a huge role in the sorption process. The plausible interactions include van der Waals, hydrophobic bonding, hydrogen bonding, pi-pi stacking, and pore-filling mechanisms, leading to a hysteretic sorption process. The optimal removal efficiency and adsorption maxima of similar to 100% and similar to 8200 mg/g are obtainable at optimum process conditions. Therefore, waste valorization and adsorption performance achieved in this study suggest a sustainable and cost-effective pathway for pollution remediation.

Automated summary

Carbon-based adsorbents were produced from onion skin waste for efficient adsorption of methylparaben from contaminated water. The carbon material showed a micro- and mesoporous structure with a graphenic carbon-like multilayer structure. Various interactions were identified between methylparaben and the adsorbent, including van der Waals forces, hydrophobic bonding, hydrogen bonding, pi-pi stacking, and pore-filling mechanisms. The optimal conditions achieved high removal efficiency and adsorption capacity, suggesting a sustainable and cost-effective pathway for pollution remediation.