Removal of cadmium (II) and lead(II) ions from aqueous solution using modified bentonite as a low-cost adsorbent: A kinetic and equilibrium study

In this article, the influence of modified bentonite on the adsorption of heavy metals ion like cadmium and lead from waste water is evaluated. Modified bentonite prepared during several steps, including Purification of the raw bentonite, Preparation of monolayer bentonite with n-cetyl pyridinium bromide(CP-bentonite), Synthesis and immobilization of a novel ligand s,s′-bis(2-mercaptoethyl)-3,3′-(dodecylazanediyl) dipropanethioate on the monolayer bentonite and preparation of bilayer bentonite (MEDPT@CP-bentonite). Th e modified bentonite were used as absorbent to remove cadmium and lead ions from waste water. Th e chemical parameters for quantities of adsorption of heavy metal contamination have been done, and the kinetics of adsorption has also been carried out. MEDPT@CP-bentonite provides enough absorbable sites to overcome mass transfer limitations. Th e number of absorbable sites for lead is more compared to cadmium, and thus the rate of recovery of lead is faster than cadmium, and the percentage removal of lead is more than cadmium. Th is difference indicates the influence of MEDPT@CP-bentonite in the adsorption of heavy metals depends on adsorption isotherm. Th e maximum removal of metal occurred with 0.1 g MEDPT@CP-bentonite. Th e uptake amount of heavy metal ions on MEDPT@CP-bentonite increased rapidly with increasing the contact time from 1to 35 h and then reaches equilibrium after 24h.