Synthesis, characterization, and textile dye adsorption studies of a kaolin-based polymer layer silicate composite

Contamination and exposure to textile dye wastewater are environmental issues of grave concern, especially in developing countries. The use of advanced technologies to remediate wastewater is not economical for small- and medium-sized industries. An environmentally friendly and economical method was developed to adsorb dyes from wastewater using a composite material, prepared by the sol-gel method. The surface area was 18.16 m(2)/g and the pH at the point of zero charge (pH(PZC)) was 4.2. The peak shifts in Fourier transform infrared spectra upon adsorption indicated the functional groups involved in adsorption while scanning electron microscopic images indicated that exfoliated and intercalated polymer layer silicate structures are present in the composite. The composite dose of 0.20 g adsorbed over 90% of fuchsine and methylene blue dyes after 240 min and 330 min, respectively. The experimental data of fuchsine adsorption agreed with the Langmuir-Freundlich combined isotherm while methylene blue adsorption data obeyed the Freundlich isotherm alone. Fuchsine dye forms Hydrogen (H)-bonds and H-pi interactions with the adsorbent surface, and H-bonds and pi-pi interactions between the dye molecules to form multilayers. The methylene blue forms H-pi interactions with the adsorbent surface. The composite can remove negatively charged dyes since the adsorption surface is positively charged even at pH 7. The composite dose of 0.20 g reduced the absorbance of dyes in wastewater within 6 h of agitation. This shows that the adsorbent has the potential to remove pigment dyes and direct dyes present in industrial wastewater. [GRAPHICS] .