Adsorption of Cu2+ on Montmorillonite and Chitosan-Montmorillonite Composite Toward Acetate Ligand and the pH Dependence
2016
Hu, Zhao | Hu, Hongqing | Zhu, Jun | Deng, Youjun | Li, Chunsheng
Chitosan-montmorillonite composite was extensively used for the removal of heavy metals from wastewater. In wastewater, copper (Cu²⁺) usually coexist with the organic ligands, which had unknown effect on Cu²⁺ adsorption by the composite materials. In order to understand further on that, the adsorption of copper by the composite materials must be studied. In the present study, montmorillonite was coated with chitosan, and X-ray diffraction (XRD) patterns of the composite proved the intercalation of chitosan in the montmorillonite. Fourier transform infrared (FTIR) spectra of the composite identified the presence of amino group on the composite, and that of the composite saturated with metals identified the interaction between the amino groups and metals. Langmuir adsorption isotherm indicated that the composite had more capacity to adsorb Cu²⁺ from wastewater than montmorillonite. The adsorption capacity of Cu²⁺ by montmorillonite and chitosan-montmorillonite composite was studied, respectively, as a function of pH and in the presence of acetate. Compared to the montmorillonite at low ligand concentration (0.08 mmol/L) or low pH (<4.0), the coexisting acetate increased more Cu²⁺ adsorption by the composite. The acetate ligand presented less depression on the adsorption by the composite than that by montmorillonite at high ligand concentration (4 mmol/L) or high pH (>4.5). Therefore, the composite is more suitable for removing Cu²⁺ than montmorillonite in acid aqueous medium.
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