SYNTHESIS AND PHYSICOCHEMICAL CHARACTERIZATION OF CHITOSAN–SiO2-BASED COMPOSITES

Abstract

Introduction. Composites based on chitosan are of particular interest owing to their biodegradability, environmental safety, and strong affinity for metal ions. Immobilization of chitosan on an inorganic support such as silica can be used as a method to improve physicochemical properties of hybrid materials such as their thermal stability and mechanical strength. Objectives. The main purpose of this work was preparation of chitosan–SiO₂ composites with different chitosan loadings and determination of their physicochemical properties. Methods. Composite chitosan–SiO₂ with 5, 10, and 20 wt.% content of chitosan was synthesized via adsorption immobilization followed by alkaline precipitation. Physical characteristics of obtained materials were studied using methods such as thermogravimetric analysis (TGA), nitrogen adsorption–desorption analysis (BET), and scanning electron microscopy (SEM). Results and discussion. In our study, we showed that alkaline precipitation greatly increased the efficiency of adsorption and immobilization of chitosan, giving immobilization yields of 93-100%. From thermogravimetric analysis, it was found that content of organic substances in the materials is gradually increased by increasing chitosan loading. According to the classification of the IUPAC, the isotherm is classified as type IV isotherms with H3 hysteresis loop characteristic for mesoporous materials. Scanning electron microscopy revealed heterogeneous and relatively rough surface morphology. Conclusion. Obtained composite materials have developed mesoporous structure, high thermal stability, and good immobilization of chitosan, which allows to consider them as prospective sorbents for heavy metal ion elimination from aqueous solutions.