Batch adsorption technique for the removal of malachite green and fast green dyes by using montmorillonite clay as adsorbent

Abstract

Due to the major environmental problems of colorants in the present study, the removal of malachite green and fast green dyes were studied on montmorillonite clay adsorbent under optimized conditions. The concentration of dyes, amount of adsorbent and agitation time was optimized. Spectrophotometric technique was adopted for the measurement of concentration of dyes before and after adsorption. The adsorption data were fitted on Langmuir, Freundlich and Dubinin-Radushkevich adsorption isotherm equations. The values of their corresponding constants were determined from the slope and intercepts of their respective plots. Thermodynamic parameters such as free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) of the system were also calculated by using Langmuir constant k. From the percentage (%) removal data, it was obtained that fast green-montmorillonite clay system and malachite green-montmorillonite clay system shows about 97 and 95% adsorption tendency. The scanning electron microscopy (SEM) technique was applied to study the surface morphology of the adsorbent. Key words: Adsorption, dyes, montmorillonite clay, adsorption isotherms, thermodynamics of adsorption.