Green synthesis of silica nanoparticles from leaf biomass and its application to remove heavy metals from synthetic wastewater: A comparative analysis

The effective removal of pollutants generated from various industries containing heavy metal ions has become an unprecedented global issue. Given the serious implications of heavy metals like lead (Pb²⁺) and copper (Cu²⁺) ions on human health, development of cost-effective and ecofriendly adsorbents for efficient removal of these heavy metals is highly desirable. In this context, silica nanoparticles (SNPs) have garnered attention for their capability to adsorb Pb²⁺ and Cu²⁺ effectively from wastewater. In the present study, SNPs were synthesized via green synthesis by utilizing leaf biomasses from Saccharum ravannae (SRL), Saccharum officinarum (SOL) and Oryza sativa (OSL) via a simple chemical method. SNPs were further applied as a potential adsorbent material for the removal of Pb²⁺ and copper Cu²⁺ from wastewater. The adsorption studies were evaluated in batch method by varying the experimental parameters viz., pH, adsorbent dose, contact time, initial metal ion concentration, and temperature. The maximum adsorption efficiency attained was more than 95 % in the case of both heavy metal ions. Further, the adsorption mechanism was explained via various kinetics, isotherms, and thermodynamic models. The adsorption isotherm was well explained by Freundlich isotherm model and kinetics via pseudo-second-order kinetics for Pb²⁺ and Cu²⁺. SOL SNPs was more promising nanomaterial then other SRL and OSL SNPs for the significant adsorption of heavy metal ions from water.