The presentwork dealswith the study of Cr (VI) adsorption ontomontmorillonite (MM) andmodified montmorillonite (MMT). The modification is done by using an amine based solvent, trioctylamine (TOA). Equilibriumand kinetic experiments are carried out to determine the effect of adsorbent dose (w, 0.05 g to 0.3 g forMM, 0.01 g to 0.06 g for MMT), initial Cr (VI) concentration (C0, 25 mg L−1 to 125 mg L−1), pH (1 to 9), and contact time (t, 10 min to 100 min) on the capacity of both the adsorbents. With an increase in the adsorbent dosage, the uptake capacity of MM and MMT for Cr (VI) is found to decrease but with an enhancement in the recovery efficiency. The optimumdosage ofMMandMMT is proposed to be 0.2 g and 0.02 g, respectively. A better adsorption of Cr (VI) is observed at lowpH values of aqueous solution, and is decreasedwith an increase in the value of pH. In the kinetic experiments, the percentage removal of Cr (VI) reaches to a constant value of 70.68%withMM(0.2 g) and 33.92%withMMT (0.02 g) after 80 min. Equilibriumdata are analysed by using Langmuir and Freundlich isotherm models. Kineticmodels such as pseudo-first order (PFO) and pseudo-second order (PSO) are used to predict the kinetics of the adsorption process by MM and MMT for the Cr (VI) removal.
