Synthesis and evaluation of a new CeO2@starch nanocomposite particles for efficient removal of toxic Cr(VI) ions

Abstract

This study presents the synthesis and characterization of a highly effective nanocomposite material, CeO₂@starch, designed for the removal of Cr(VI) from aqueous solutions. Through a series of experiments and analyses, we investigated the adsorption efficiency of the CeO₂@starch nanocomposite by considering various factors such as contact duration, pH levels, initial Cr(VI) concentration, and temperature. Firstly, we successfully synthesized the CeO₂@starch nanocomposite and conducted comprehensive characterizations using BET, FTIR, and SEM analyses. These characterizations provided valuable insights into the structure and properties of the nanocomposite, confirming its potential as a promising adsorbent for Cr(VI) removal. In our experiments, we observed that the CeO2@starch nanocomposite exhibited an impressive capacity for reducing Cr(VI) ions to Cr(III) in aqueous solutions. Notably, the adsorption efficiency was found to be at its maximum at pH 2, and equilibrium was achieved within 240 min of contact time. The kinetics of the adsorption process were accurately described by the pseudo 1st order equation, which displayed a high correlation coefficient (greater than 0.99), indicating the reliability of this model. Furthermore, we compared various adsorption isotherm models to describe the data obtained, including Freundlich, Sips, Redlich-Peterson, Temkin, and Langmuir models. The Langmuir isotherm model demonstrated the best fit, emphasizing the monolayer adsorption of Cr(VI) onto the CeO₂@starch nanocomposite and confirming its superior performance compared to other models. The Langmuir adsorption capacity of the nanocomposite material was measured at 22℃ and found to be 48.54 mg/g. Interestingly, the adsorption capacity increased with higher temperatures, suggesting an endothermic adsorption process. To gain further insights into the nature of the adsorption, we performed thermodynamic analysis, revealing that the adsorption of hexavalent Cr onto the CeO₂@starch nanocomposite was spontaneous and had a chemical nature.