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The Adsorption of Cd(II) on Manganese Oxide Investigated by Batch and Modeling Techniques

1
Laboratory of Nano-Minerals and Environmental Materials, School of Resources and Environmental Engineering, Hefei University of Technology, Hefei 230009, China
2
School of Environmental Science and Engineering, Xiamen University of Technology, Xiamen 361024, China
*
Authors to whom correspondence should be addressed.
Int. J. Environ. Res. Public Health 2017, 14(10), 1145; https://doi.org/10.3390/ijerph14101145
Received: 2 September 2017 / Revised: 22 September 2017 / Accepted: 22 September 2017 / Published: 28 September 2017
(This article belongs to the Special Issue Environmental Cadmium Exposure and Public Health)
Manganese (Mn) oxide is a ubiquitous metal oxide in sub-environments. The adsorption of Cd(II) on Mn oxide as function of adsorption time, pH, ionic strength, temperature, and initial Cd(II) concentration was investigated by batch techniques. The adsorption kinetics showed that the adsorption of Cd(II) on Mn oxide can be satisfactorily simulated by pseudo-second-order kinetic model with high correlation coefficients (R2 > 0.999). The adsorption of Cd(II) on Mn oxide significantly decreased with increasing ionic strength at pH < 5.0, whereas Cd(II) adsorption was independent of ionic strength at pH > 6.0, which indicated that outer-sphere and inner-sphere surface complexation dominated the adsorption of Cd(II) on Mn oxide at pH < 5.0 and pH > 6.0, respectively. The maximum adsorption capacity of Mn oxide for Cd(II) calculated from Langmuir model was 104.17 mg/g at pH 6.0 and 298 K. The thermodynamic parameters showed that the adsorption of Cd(II) on Mn oxide was an endothermic and spontaneous process. According to the results of surface complexation modeling, the adsorption of Cd(II) on Mn oxide can be satisfactorily simulated by ion exchange sites (X2Cd) at low pH and inner-sphere surface complexation sites (SOCd+ and (SO)2CdOH species) at high pH conditions. The finding presented herein plays an important role in understanding the fate and transport of heavy metals at the water–mineral interface. View Full-Text
Keywords: cadmium; Mn oxides; adsorption; surface complexation modeling cadmium; Mn oxides; adsorption; surface complexation modeling
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Huang, X.; Chen, T.; Zou, X.; Zhu, M.; Chen, D.; Pan, M. The Adsorption of Cd(II) on Manganese Oxide Investigated by Batch and Modeling Techniques. Int. J. Environ. Res. Public Health 2017, 14, 1145.

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