Enhanced Dye Adsorption by Microemulsion-Modified Calcined Diatomite (μE-CD)

Abstract

This study attempted to improve the adsorption performance of calcined diatomite for the removal of colour from wastewaters through modification with microemulsions. The surface area, pHZPC, Fourier transform infrared (FTIR) of calcined diatomite and μE-CD were studied. It is found that an increase in the BET surface area, pHZPC and total pore volume after modification was obtained. A decrease in average pore volume was observed after modification. This suggests that the pore opening deceased to be in the micro- and meso-pore region hence the adsorption capacity for the modified adsorbent will be enhanced by reducing the escaping of dye molecules. The influence of concentration, pH and particle size on the adsorption capacities of methylene blue (MB), hydrolysed reactive black (RB) and hydrolysed reactive yellow (RY) was investigated. It was concluded from FTIR and pH analysis that the predominant mechanism of RY molecules onto μE-CD is by an electrostatic attraction between the carboxylate anion and the dye. In the case of MB and RB, the adsorption mechanism could be a combination of different mechanisms such as electrostatic attraction, capturing by microemulsion micelles in the pores of the calcined diatomite or the hydrophobic attraction. The adsorption capacities were higher than unmodified calcined diatomite. In the case of adsorption of MB molecules, a high adsorption capacity onto μE-CD was obtained.