Dissolution kinetics studies of kaolin ore as raw material for mesoporous silica by acid leaching

Abstract

The high demand for nanoporous silica materials makes it worthwhile to further explore new, cheap and environmentally friendly resources. In this study, the selective acid dissolution of an indigenous kaolin ore after thermal activation for the preparation of mesoporous silica nanoparticles was reported. Experimental parameters (acid concentration, liquid/solid ratio and temperature) were optimised and resultant solid was characterised by X-ray diffraction; scanning and transmission electron microscopy and nitrogen adsorption–desorption measurements. The products were found to be nanoporous with pore sizes of 0.402 and 0.129 cm3 g–1, with specific surface areas of 45.23 and 16.89 m2 g–1, respectively. The pore development follows the Avrami model with parameter model n values of 0.80 and 0.63, and calculated apparent activation energies of 7.22 and 22.81 kJ mol–1 for hydrochloric and sulphuric acid respectively, suggesting that the leaching activity is controlled by diffusion processes. The products as characterised demonstrated the vast potential of kaolinite in the development of mesopore materials for diverse industrial applications.