Adsorption Capability of Ionic Dyes onto Pristine and Calcined Activated Clay

Abstract

In this study, pristine and calcined activated clay (AC) were characterized by scanning electron microscopy, X-ray diffraction analysis, thermogravimetric-differential thermal analysis, electron probe microanalysis, surface pH measurement, specific surface area measurement, and humidity adjustment. ACs were used as adsorbents for investigating the adsorption kinetics, isotherms, thermodynamic parameters, of Basic Red 46 (BR), Basic Blue 75 (BB), Acid Red 138 (AR), and Acid Blue 185 (AB) in aqueous solutions, as well as the effect of sodium hydroxide on these dyes. The results showed that adsorption of cationic and anionic dyes was related to the specific surface area (0.974–0.984) and humidity adjustment performance (0.939–1.000), respectively. The adsorption capacity of the cationic dyes (BB and BR) onto pristine AC increased on increasing the temperature. Equilibrium data using pristine AC fitted well to both the Langmuir and Freundlich isotherm models. Kinetic data were best described by the pseudo-second order model (correlation coefficient was 0.979–0.999 and 0.945–0.999 for BB and BR). Nearly 8 h of contact time was sufficient for the adsorption of cationic dyes to reach equilibrium. Thermodynamic parameters were also evaluated for the cationic dye-adsorbent system, which revealed that the adsorption process is endothermic in nature. These results demonstrated that pristine AC could be used as a natural adsorbent for the removal of cationic dyes (BB and BR) from aqueous solution. [DOI: 10.1380/ejssnt.2016.209]