Estimation and removal of chromium ions from tannery wastes using zeolite-3A

The concentration of potentially toxic chromium metal ions in sediments and liquid waste samples from selected tanneries was measured by atomic absorption spectrophotometry after digestion with nitric acid. The data obtained revealed the presence of elevated levels of chromium metal ions in waste samples relative to the NEQS (National Environmental Quality Standards) requirements. A new process entitled IERECHROM (Ion Exchange REmoval of CHROMium) has been developed for the removal and separation of chromium ions from sediments using zeolite-3A. The factors affecting chromium ion removal include exchanger concentration, pH, shaking time and temperature. The appliability of the Freundlich, Dubinin-Radushkevich and virial isotherm equations to the system has been examined. The thermodynamic parameters ΔH^O, ΔG^O and ΔS^O were calculated using the virial isotherm expression. The results suggest that natural aluminosilicates such as zeolite-3A can be utilised as low-cost ion-exchange and sorbent materials because of their selectivities for the removal of chromium ions and various other heavy metals.