Synthesis and characterization of kaolinite and TiO₂ nanocomposites using the polymer precursor method

ABSTRACT

The present work used kaolinite as base material to obtain nanocomposite materials. Kaolinite was used in its natural form, heat treated at 700 ºC and chemically using 6 mol L^-1 phosphoric and sulfuric acids. The objective of the acid treatments was to modify and prepare the kaolinite structure to be used as a support for TiO₂. Using the polymeric precursor method, TiO₂ and nanocomposites based on kaolinite and TiO₂ were synthesized. Nanocomposites were characterized by X-ray Diffraction (XRD), UV-Vis, to determine Band Gap, Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Dispersive Energy Spectroscopy (EDS). Through the FTIR spectra it was possible to verify the characteristic bands of in natura kaolinite, and the appearance of characteristic vibrations of metakaolin. XRD analysis revealed that it was possible to promote increased crystallinity of kaolinite samples after treatment with titanium citrate, this may be due to the adhesion of oxide on the kaolinite surface. By EDS analysis it was possible to determine the percentage of Ti (m/m) in the synthesized samples, and its value was between 2.03 and 4.16%. ICP-OES analyzes indicate that samples have 2.65 to 4.07% Ti and Bandgap data range from 1.69 to 3.44 eV for samples with and without Ti in their composition.

Keywords
Kaolinite; metakaolinite; acid activation; Polymeric Precursor Method; Titanium Dioxide