Equilibrium, Kinetic and Thermodynamic Studies of Nickel Adsorption Onto Natural and Modified Kaolinites

Abstract

Availability of clay and its modified forms makes them a viable candidate for an alternative adsorbent. In this study, kaolinite and modified kaolinites were tested to determine their suitability for removal of Ni (II) ions from aqueous medium. Parameters, such as kaolinite type, concentration of Ni ions, time and temperature of interaction, were investigated to evaluate the adsorption capacity, kinetics, equilibrium and thermodynamic properties of Ni (II) adsorption. The adsorption isotherms followed Freundlich, Dubinin-Redushkevich (D-R) and Halsey isotherms but DR isotherm was chosen due to its applicability to all adsorption isotherms. The kinetics of adsorption mechanism of Ni (II) was tested using pseudo-first-order, pseudo-second-order and intraparticle diffusion models. The results showed that adsorption mechanism could be perfectly explained with pseudo-second order equation. The intraparticle diffusion of Ni (II) ions within the natural and modified kaolinite was more likely to be governed by the diffusion step. Adsorption mechanism for activated kaolinite was intra-particle diffusion model. Ni (II) adsorptions on activated kaolinites were exothermic and spontaneous in nature. The results of this study indicated that activated kaolinite can be employed for removal of Ni (II) from industrial wastewater.