Kinetics and thermodynamics studies on the adsorption of Zn(II), Cd(II) and Hg(II) from aqueous solution using zinc oxide nanoparticles

• Published in: Powder technology 2012-02, Vol.217, p.163-170
• Main Authors: Sheela, T., Nayaka, Y. Arthoba, Viswanatha, R., Basavanna, S., Venkatesha, T.G.
• Format: Article
• Language: English
• Subjects: adsorbents; Adsorption; Adsorption isotherms; Applied sciences; Aqueous solutions; Cadmium; Chemical engineering; Exact sciences and technology; heat production; ions; Isotherms; Kinetics; Mathematical models; Mercury; Miscellaneous; Nanoparticles; Powder technology; Solid-solid systems; sorption isotherms; temperature; Thermodynamics; zinc; Zinc oxide; ZnO
• ISSN: 0032-5910; 1873-328X
• DOI: 10.1016/j.powtec.2011.10.023

The aim of this study is to investigate the utilization of the zinc oxide nanoparticles (ZnO) as an adsorbent for the removal of Zn(II), Cd(II) and Hg(II) ions from aqueous solution. Adsorption properties of ZnO towards Zn(II), Cd(II) and Hg(II) ions were systematically investigated, including pH effect, adsorption equilibrium, adsorption kinetics and temperature. The adsorption isotherms were well described by Langmuir isotherm model with correlating constant (R2) higher than 0.99. The maximum adsorption capacity was determined at 303K and were found to be 357, 387 and 714mg/g for Zn(II), Cd(II) and Hg(II) ions respectively. The adsorption kinetics data were well fitted by the pseudo-second-order rate model with high regression coefficients. The adsorption capacity was decreased with the increase of temperature, and thermodynamic calculations suggested that the adsorption of Zn(II), Cd(II) and Hg(II) ions onto ZnO nanoparticles is an exothermic process. The confirmation of the process of adsorption of metal ions on ZnO nanoparticles was done by EDX analysis. The above Figure shows EDX pattern for ZnO before and after adsorption. The EDX pattern of ZnO after adsorption shows the characteristic signals of different metals. This shows the diffusion or accumulation of metal ions onto the surface of ZnO nanoparticles. [Display omitted] ► qmax for Zn, Cd and Hg ions were 357, 387 and 714 mg/g respectively. ► qmax of ZnO is comparatively more than the other adsorbents reported elsewhere. ► ZnO nanoparticles were prepared by simpler method and low cost materials were used.