SORPTION DYNAMICS OF MODIFIED NUT SHELLS ON NI II CO II CR VI IONS FROM AQUEOUS SOLUTIONS AND INDUSTRIAL EFFLUENTS EQUILIBRIUM ISOTHERMAL AND KINETIC STUDIES

Abstract

Metal pollution of water and its sources has been receiving considerable attention in recent times due to the increasing amounts of industrial effluents discharged into the environment. Heavy metals like nickel, chromium, copper, cobalt, mercury, lead, cadmium and zinc in their common oxidation states are reported to cause several physiological disorders and pose hazardous threat to the environment. Several reclamation technologies have been developed to reduce their concentrations. A number of low-cost and indigenous materials are identified as successful adsorbents, to remove metal ions through the process of adsorption. In this context, acid-base treated, phosphate modified and nanomodified adsorbent materials, which have been prepared from Terminalia catappa nut shell and Azaridachta indica nut shell are employed to reduce the concentrations of the three selected metal ions. Adsorption studies of Ni(II), Co(II) and Cr(VI) employing the chosen sorbents have been investigated by batch equilibration method. The characteristics of the treated sorbents are determined and the adsorptions of metal ions onto the surface of the adsorbents are confirmed by Microscopic, AFM, BET, BJH, SEM, FT-IR and EDAX analytical techniques. The optimum conditions for achieving maximum adsorption of metal ions are established. Phosphate modified and Nano modified sorbents are subjected to the optimized conditions of parameters study. The factors influencing the adsorption rate and the dynamics of adsorption processes are studied in order to verify the adsorption behaviour. The nature of adsorption equilibrium and kinetic behaviour are explained by different isothermal and kinetic models respectively. A comparative assessment of the sorption ability of the treated adsorbents along with the order of preferential adsorption among the metal ions is made on the basis of the valid conclusions drawn from the experimental results. The efficiency of the adsorbent materials is tested with industrial effluents.