Kinetic and Thermodynamic Sorption Study of Cobalt Removal From Water Solution With Magnetic Nano-Hydroxyapatite

Abstract

In this study, Magnetite-hydroxyapatite nanocomposites were prepared by in situ precipitation of the calcium phosphate phase in an iron oxide colloidal suspension. Adsorption of cobalt was initially rapid and the adsorption process reached a steady state after 180 min. The Co(II) adsorption capability of the MHAp was investigated as a function of temperature, pH, ionic strength, adsorbent dosage, agitation speed and initial Co(II) concentration. Theincrease in pH and temperature resulted in an increase in Co(II) adsorption capacity; Increasing ionic strength increased the adsorption of Co(II) by MHAp; The adsorption isotherms were well described by the Freundlich model, Langmuir, Temkin and D-R models. The Freundlich model was found to provide the better fit with the experimental data. Different types of adsorption kinetic models were used to describe the Co (II) adsorption behaviour, and the experimental results fitted the pseudo-second-order kinetic models well. Thermodynamics parameters such as ∆H o , ∆S o , ∆G o revealed that the adsorption of Co(II) by MHAp was endothermic in nature, physisorption, spontaneous at 308 and 318K.