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

Document Type : Research Paper




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