Removal of Cu(II) from aqueous solution by adsorption on Chinese Quaternary loess: Kinetics and equilibrium studies

Abstract

This paper dealt with the characteristics of Cu(II) adsorption on Chinese Quaternary loess. The Cu(II) adsorption isotherm and kinetics fit the Langmuir model and pseudo-second order kinetics well, respectively, with a predicted adsorption capacity of 109 mg g⁻¹. The adsorption is ion exchange adsorption due to D-R model. Factors that are positively correlated with the adsorption capacity of loess include equilibrating time, pH, temperature, and solid-solution ratio. The adsorption of Cu(II) on loess involves 2–3 sequential diffusing steps into the micropores, and an endothermic and spontaneous process with predicted enthalpy, entropy, and Gibb's free energy changes of 7.64 kJ mol⁻¹, 81.21 J mol⁻¹K⁻¹ and −14.94–17.37 kJ mol⁻¹, respectively. Moreover, the applicability of loess on industrial wastewater treatment was investigated and satisfactorily proved. Finally, FT-IR spectra shows the precipitation of copper carbonate and the complexation of Cu(II) with clay minerals at pH > 5.0 and pH > 2.67, respectively.

Keywords:

• Chinese Quaternary loess
• Cu(II)
• adsorption
• kinetics
• thermodynamics
• industrial wastewater

Acknowledgments

The authors would like to express their sincere gratitude to the Key Project of National Natural Science Foundation of China (NSFC) (Grant 50538080) and National Science Fund for Distinguished Young Scholars (Grant 50425825) for the financial support of this study.