Kinetic and Thermodynamic Studies of Heavy Metal Remediation by Modified Bentonite

Geochemical reactions and anthropogenic activities are a source of heavy metal concentration in aquatic bodies leading to serious detrimental effect to the environment because of its non-biodegradability. Bentonite, a smectite group of minerals has layered structure based on sheets having 2:1 structure i.e. one octahedral sheet sandwiched by 2 tetrahedral sheets. The bentonite was characterised by PXRD, FTIR, TGA and DSC experiments and the surface area was known by BET analysis. A weight loss of 14% and diffraction pattern of PXRD confirmed presence of Montmorillonite unit in the inner part. Bentonite acts as a natural scavenger of heavy metal toxicants .Owing to high cation exchange capacity, high surface area and intercalation properties, bentonite mineral has been used as a potential remover of heavy metals. The kinetic and thermodynamic studies were done in order to determine the remediation potential at pH 2 to 8. Langmuir, Freundlich and Temkin adsorption isotherms were employed to give an insight into the adsorption mechanism. The experimental data revealed that first order kinetics was followed during the adsorption of heavy metals onto modified bentonite. Maximum percentage removal of Cr(VI) and Mn(VII) was 80 and 55.5 respectively. Thus locally available bentonite may be utilised as a low cost and eco-friendly alternative of heavy metal removal.