Sonochemical synthesis, characterization and sorption study of Kaolin-Chitosan-TiO2 ternary nanocomposite: Advantage over conventional method

Abstract

The present study deals with the successful preparation of kaolin/chitosan/titanium dioxide (KL-CTS-TiO2) ternary hybrid nanocomposite adsorbent using conventional and ultrasound assisted method synthesis. The particle size (observed form TEM image) of TiO2 nanoparticles dispersed in the nanocomposite was found to be around 5 nm for U-KL-CTS-TiO2 nanocomposite (ultrasonically prepared), which is lesser compared to conventionally prepared nanocomposite. The average particle size of U-KL-CTS-TiO2 nanocomposite was observed to be 293 nm which is very less compared to C-KL-CTS-TiO2 nanocomposite (prepared by conventional method) that is 439 nm. The BET surface area of U-KL-CTS-TiO2 nanocomposite was found to be 116.5 m2/g which is significantly higher than the C-KL-CTS-TiO2 nanocomposite (4.95 m2/g). In batch adsorption experiments the effect of initial dye concentration, time, temperature, and adsorbent dose was studied and equilibrium data, adsorption kinetics and adsorption isotherms parameters are reported. The adsorption equilibrium data was best fitted by Freundlich isotherm compared to the Langmuir and Temkin model for U-KL-CTS-TiO2 and C-KL-CTS-TiO2 nanocomposite. The % removal of CV dye for 2 g/L loading of U-KL-CTS-TiO2 and C-KL-CTS-TiO2 nanocomposite was found to be 93.30% and 85.49%, respectively. The higher adsorption in the case of U-KL-CTS-TiO2 nanocomposite is attributed to the physical effects of ultrasound which are responsible for the preparation of finely dispersed KL-CTS-TiO2 nanocomposite compared to conventional method. Finely dispersed KL-CTS-TiO2 nanocomposite provides more sites for the adsorption which in turn enhances the adsorption capacity of CV dye on ultrasonically prepared KL-CTS-TiO2 nanocomposite.