Experimental and isotherm modelling process of lead(II) adsorption on silica nanocapsule adsorbents

Abstract This research study investigates the ability of silica nanocapsule (SiNC) adsorbents to remove Pb(II) ions from water, utilizing different isotherm models for analysis. The SiNCs were effectively synthesized via a microemulsion polymerization method followed by calcination. To investigate the adsorption characteristics of SiNCs in the removal of Pb(II) ions, batch adsorption tests were conducted. The findings indicated maximum adsorption capacity for Pb(II) ions onto SiNCs was 26.21 mg/g, with maximum removal of 99.84% at an optimal pH of 6 under standard conditions. The performance of the adsorption process was further analyzed through various linear and non-linear models, such as Langmuir, Freundlich, Sips, Fritz-Schlunder, Khan, Redlich-Peterson, Henry, Baudu, Temkin, and Hills. The Redlich-Peterson model fit the linear data best, while the five-parameter Fritz-Schlunder model was the most accurate for non-linear data. Error analysis indicated that the non-linear chi-square (X 2 ) function was the most effective for the Fritz-Schlunder model, yielding the lowest deviation of 0.070 from experimental data. The study also revealed that non-linear models consistently outperform their linear counterparts in terms of accuracy, providing strong evidence that non-linear regression is a more precise and reliable approach for adsorption modelling.