Separation of chromium (VI) from its liquid solution using new montmorillonite supported with amine based solvent

The present work deals with the study of Cr (VI) adsorption onto montmorillonite (MM) and modified montmorillonite (MMT). The modification is done by using an amine based solvent, trioctylamine (TOA). Equilibrium and kinetic experiments are carried out to determine the effect of adsorbent dose (w, 0.05 g to 0.3 g for MM, 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 optimum dosage of MM and MMT is proposed to be 0.2 g and 0.02 g, respectively. A better adsorption of Cr (VI) is observed at low pH values of aqueous solution, and is decreased with 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% with MM (0.2 g) and 33.92% with MMT (0.02 g) after 80 min. Equilibrium data are analysed by using Langmuir and Freundlich isotherm models. Kinetic models 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.