Thermodynamic Study of Hg(II) Ion Adsorption onto Nano Hydroxyapatite from Aqueous Solution

Abstract

Hydroxyapatite nanocrystals were synthesized by sol-gel combustion method for the sorption of<br />Hg(II) ions from aqueous solutions. The effects of varying parameters such as pH, temperature, initial<br />metal concentration, and contact time on the adsorption process were examined. Adsorption<br />equilibrium was established in 360 minutes and the maximum adsorption of Hg(II) on the<br />hydroxyapatite was observed to occur at pH 7.0. The adsorption data correlated with Freundlich and<br />Langmuir isotherms. The Langmuir isotherm showed a better fit to the equilibrium data. The<br />adsorption thermodynamic parameters (ΔG 0, Δ H 0, and Δ S 0) were calculated which showed an<br />endothermic adsorption process. The equilibrium parameter (RL) indicated that hydroxyapatite<br />nanocrystals are useful for Hg(II) removal from aqueous solutions.