KINETICS AND THERMODYNAMIC ASSESSMENT OF CHROMIUM AND CADMIUM REMOVAL FROM AQUEOUS SOLUTION USING ACTIVATED CARBON PREPARED FROM PERIWINKLE SHELL

ABSTRACT

Activated carbon prepared from periwinkle shell is used to adsorb selected heavy metals such as cadmium and chromium. Heavy metals are toxic and may be found in both surface and underground water. Periwinkle shell which is an agricultural waste was activated with KOH then later used for the removal of these toxic metals from their aqueous solutions.

It was observed that the optimum time and dosage for adsorption of both (Cd and Cr) was 60minutes and 0.5g respectively. It was also observed that as concentration increases from 1.0 to 5.0mg/L adsorption increased. The pH of the activated carbon was 6.9 which is neutral, the Bulk density was 0.0377 g/cm³ and the Surface area was 76.12m² /g.

The Kinetics Adsorption shows best fit for Pseudo Second Order, From the thermodynamics study, the entropy change (∆S°) was negative indicating the decreased randomness at solid liquid interphase during the sorption processes of Cd²⁺ and Cr⁶⁺ ions on the activated periwinkle shell, It was also evident that the values of (∆H°) were positive, that is endothermic, with endothermicity increasing at higher adsorbate concentration.