Adsorption process of the malachite green onto clay: kinetic and thermodynamic studies
Mohammed Messaoudi, Mohamed Douma, Najib Tijani, Younes Dehmani, Lahcen Messaoudi
Abstract
ABSTRACT This work reports the study of the adsorption of malachite green (MG) dye on Moroccan clay according to different parameters impacting the adsorption phenomenon, such as pH, the temperature of the medium and the MG dye concentration. The clay used as adsorbent was initially characterized by X-ray fluorescence spectrometry, Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction, Brunauer–Emmett–Teller, and thermogravimetric analysis. The results indicate that the equilibrium of MG adsorption is reached in 90 min. The efficiency of dye removal on clay increases with the contact time, initial dye concentration, solution temperature and pH. The experimental data obtained were examined using isothermal and kinetic models based on the errors calculated values of R 2 (correlation coefficient) and χ 2 (chi-square). It was found that the nonlinear forms of the Langmuir isotherm and the pseudo-second-order kinetic model are the best-fitting with experimental data. The thermodynamic study showed that the adsorption was a spontaneous and exothermic process. However, FTIR analysis of the adsorbent, before and after MG adsorption, shows that the mechanism of MG adsorption occurs through the phenomenon of chemical interaction between the adsorbate and the adsorbent.