Adsorption performance and mechanistic study of Pb, Cd and As by CaAl-LDH in wastewater

Heavy metal composite pollution is becoming increasingly serious. In this study, CaAl-layered double hydroxide (CaAl-LDH) was prepared using the facile co-precipitating method, and was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). Lead(II), Cd(II), and As(V) were selected as the representative heavy metals to evaluate the adsorption capability of the synthesized CaAl-LDH by the batch experiments. The maximal adsorption capability of CaAl-LDH for Pb(II), Cd(II), and As(V) was 786.6, 437.2 and 72.9 mg/g, respectively. The adsorption mechanism of Pb, Cd and As may be surface precipitation, isomorphic substitution and ion exchange within the interlayer spaces of LDH, respectively. In conclusion, this experiment provides a LDH material with fast and efficient adsorption performance for both anionic and cationic metals, indicating its potential for practical application in the remediation of heavy metal composite pollution.