Heavy metals are considered as hazardous pollutants due to their toxicity even at low concentration and non-biodegradable properties. Now a days heavy metal ions such as cadmium, zinc, copper, lead, nickel etc are the most important pollutants in source and treated water and are becoming a severe public health problem. The fate and transport of metal ions in natural water as well as in water treatment/industrial waste water treatment processes are often controlled by their reactions with adsorbents under different environmental conditions. Iron oxide, aluminium oxides and clay minerals such as kaolin are the most wide-spread minerals of the earth crust which are known to be good adsorbent of various metal ions, inorganic anions and organic ligands.
In this work laboratory batch kinetic and equilibrium Cu (II) and Ni (II) adsorption isotherm studies are conducted to determine the adsorption capacity of iron oxide and kaolin, kinetic rate constants and equilibrium adsorption isotherm parameters under different experimental conditions. It has been found that amount of metal ion adsorption increases with increase in metal ion concentration, solution pH but decreases with increase in adsorbent concentration. The equilibrium adsorption results have been compared with Langmuir and Freundlich isotherm respectively. Finally, mechanistic surface complexation models (SCMs) have been shown to be capable of describing metal ion adsorption processes onto iron oxide and kaolin surfaces within these small metal ion concentration range and different adsorption parameters have been determined from model simulation.

Key words: metal ion adsorption, kinetic, isotherm, surface complex model