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摘要
Mg–Al–Cl layered double hydroxide(Cl-LDH) was prepared to simultaneously remove Cu(Ⅱ)and Cr(VI) from aqueous solution. The coexisting Cu(Ⅱ)(20 mg/L) and Cr(VI)(40 mg/L) were completely removed within 30 min by Cl-LDH in a dosage of 2.0 g/L; the removal rate of Cu(Ⅱ) was accelerated in the presence of Cr(VI). Moreover, compared with the adsorption of single Cu(Ⅱ) or Cr(VI), the adsorption capacities of Cl-LDH for Cu(Ⅱ) and Cr(VI) can be improved by 81.05% and 49.56%, respectively, in the case of coexisting Cu(Ⅱ)(200 mg/L) and Cr(VI)(400 mg/L). The affecting factors(such as solution initial p H, adsorbent dosage, and contact time) have been systematically investigated. Besides, the changes of p H values and the concentrations of Mg2+ and Al2+in relevant solutions were monitored. To get the underlying mechanism, the Cl-LDH samples before and after adsorption were thoroughly characterized by X-ray powder diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. On the basis of these analyses, a possible mechanism was proposed. The coadsorption process involves anion exchange of Cr(VI) with Cl-in Cl-LDH interlayer, isomorphic substitution of Mg2+ with Cu2+, formation of Cu2Cl(OH)3precipitation, and the adsorption of Cr(VI) by Cu2Cl(OH)3. This work provides a new insight into simultaneous removal of heavy metal cations and anions from wastewater by Cl-LDH.
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