Influence of Temperature on Nickel Sorption on Clay Mineral and Oxide

Introduction: Many kinetic studies have shown that sorption of metals on natural materials results in the formation of metal precipitates. However, the influence of temperature on the kinetic formation of these metal precipitates has not been studied. The effect of temperature on reaction rates is well known and important in understanding reaction mechanisms. For most reactions, the increase in rate with increasing temperature is nonlinear and reaction-rate data obeyed the Arrhenius equation: k = Ae . Energies of activation below 42 kJ mol generally indicate diffusion-controlled processes and higher values represent chemical reaction processes [1]. For example, Ea values for gibbsite dissolution in various acid solutions ranged from 59 to 67 kJ mol [2] while pesticide sorption on humic acid had an Ea value of 6.7 kJ mol [3]. Additionally, one can determine the enthalpy, entropy, and free energy of formation by applying the Eyring equation k = (kbT / h) e -ΔG‡ / RT = (kbT / h) e -ΔS‡ / R e ΔH‡ / .