Equilibrium, kinetic and thermodynamic study for the efficient removal of malachite green dye onto untreated Morus nigra L. (mulberry tree) leaves powder and its biochar

Abstract

In the present investigation the removal of malachite green (MG) dye from its aqueous solution by batch mode adsorption study onto mulberry leaves powder (MLP) and mulberry leaves biochar (MLB) has been proved to be efficient with removal percentage more than 95 % at 0.3 gm dose in 35.8 mg/L (20 ml) MG dye solution for 35 minutes. In this batch mode adsorption study various parameters like contact time, effect of dose, concentration, temperature and pH have been studied to investigate the effect of such parameters on MG dye adsorption process onto mentioned adsorbents. Among three commonly used isotherms (Langmuir, Freundlich, and Temkin), Freundlich isotherm model is best fit model with R2 = 0.99. The kinetic study reveals that pseudo-second-order kinetic model is best followed having also R2 = 0.99. Thermodynamically, the adsorption process of MG dye onto MLP is endothermic, exothermic onto MLB, and spontaneous in nature. Accordingly, the results obtained have shown that the adsorbents (MLP and MLB) can be used as low cost, rapid, and effective adsorbents for the removal of malachite green dye from its aqueous solution, thus also from wastewater.