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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 pH,adsorbent dosage,and contact time) have been systematically investigated.Besides,the changes of pH values and the concentrations of Mg2+ and Al3+ 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)3 precipitation,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.