Activation of kaolinite by a low-temperature chemical method and its effect on methylene blue adsorption

Abstract

Naturally occurring kaolinite (Kaol) was successfully activated at low temperature (250 °C) via the formation of Fe3O4 nanoparticles within the kaolinite (Kaol) structure to improve the adsorption ability of Kaol. Wet impregnation of Kaol with Fe(NO3)3·9H2O and urea and subsequent heat treatment led to the formation of Fe3O4 nanoparticles (NPs) within the Kaol structure, which could destroy the crystal structure of Kaol and transform it into an amorphous solid. The activation degree of Kaol was sensitively dependent on Fe3O4 content in Kaol/Fe3O4 nanocomposite and increased with the increase of Fe3O4 content. The BET specific surface area of activated Kaol (AKaol) increased from 7.5 to 140.5 m2 g−1, when the Fe3O4 content increased from 0 to 40%. The obtained AKaol powder exhibited a significantly enhanced adsorption abilities towards methylene blue when compared with its parent Kaol, with a monolayer adsorption capacity of 171.0 mg g−1.