HAUTE EFFICACITÉ D'ADSORPTION DU COLORANT BASIQUE (CRISTAL VIOLET) SUR LA MONTMORILLONITE ALGÉRIENNE
HIGH EFFICIENCY ADSORPTION PERFORMANCE OF BASIC DYE (CRYSTAL VIOLET) ONTO ALGERIAN MONTMORILLONITE
The Algerian montmorillonite clay in raw and purified form was evaluated as adsorbent for Crystal Violet (CV) cationic dye. The experimental results show that, the adsorption was pH independent when the adsorption capacity of CV dye was unchanged for large initial pH. The pseudo-second-order kinetic model provided the best fit to the experimental data for the adsorption of dye by both clays. The equilibrium adsorption data were analyzed by Langmuir, Freundlich and Dubinin-Radushkevich isotherm models. The best fit of experimental data was obtained by the Langmuir isotherm model. The maximum adsorption capacity of the raw clay calculated by the Langmuir isotherm model is 330 mg·g-1 at 20 °C. It is increased in fractionated sodic clay sample (381 mg·g-1). The effect of temperature on the adsorption of crystal violet was investigated. The results show that the enthalpy of adsorption of CV is negative signifying that the process is exothermic. Physisorption is the prevailing mechanism for dye adsorption. Negative value of entropy shows an ordering of the adsorbed dye at the surface of adsorbent throughout the adsorption process. The negative value of ΔG° indicates the spontaneity of adsorption process. The increase in ΔG° value when the temperature was increased indicate a decrease in feasibility and spontaneity of adsorption at higher temperatures which confirm the physisorption nature of crystal violet.
