Statistical analysis on the removal of malachite green dye using active carbons of Achyranthes aspera and Allamanda blanchetii plants

Abstract

Activated carbons were prepared from the stem parts of Achyranthes aspera and Allamanda blanchetii plants and were investigated as adsorbents for the removal of malachite green dye from contaminated water. Various extraction conditions such as pH, initial concentration of dye, adsorbent dosage, temperature, agitation time and presence of co-ions were optimized for the maximum possible extraction of the dye. For analyzing the combined effect of these parameters on the removal efficiency of the adsorbents, statistical optimization modelling was adopted. The adsorbents developed were characterized and the adsorption abilities were observed to be 40.0 mg/g and 53.0 mg/g for the active carbons of Achyranthes aspera and Allamanda blanchetii plants respectively. The mechanism of adsorption was studied using various isotherm models and it was found that the Freundlich model describes well the adsorption process. Thermodynamic studies revealed the endothermic and spontaneous nature of physisorption. The kinetics of adsorption were well defined by the pseudo-second-order model. Desorption and regeneration studies of the spent adsorbents indicated that the percentage of extraction has not come down below 80.0% even after five regenerations for both the adsorbents. The validity of the methods developed are tested with real dye-polluted industrial effluent samples.