Ultrafast dye removal using capped TiO2 nanocrystallites

Abstract

Capped and uncapped TiO2 nanocrystallites of anatase phase were prepared via precipitation method. Oleic acid was used as an effective capping agent during precipitation. The synthesized TiO2 nano crystallites were characterized using PXRD, IR, and UV. The crystallite size calculated using Debye Scherrer equation indicated that the prepared materials are in nano size. Nano crystalline TiO2 was used as a dye adsorbent. It was found that the prepared nanocrystallites have excellent dye adsorption properties towards methylene blue (MB) dye. The effect of pH, contact time, initial dye concentration, and adsorbent dosage on the adsorption capacity was systematically investigated. It was found that nanocrystalline TiO2 could remove more than 95% dye concentration in 10 minutes. The dye adsorption capacity of capped TiO2 has been determined to be 300 mg g-1 at the initial solution pH of 10. Freundlich, Langmuir, and Dubnin-Radushkevich-Kaganer isotherm models were applied to investigate the adsorption process. Freundlich isotherm model shows the best fit to the equilibrium adsorption at all the studied experimental conditions. Adsorption kinetics was analyzed by pseudo-first order, pseudo-second order, and intra-particle diffusion kinetic models. It was found that methylene dye adsorption follows the pseudo second-order kinetics.