Polyaniline-Modified Mg/Al Layered Double Hydroxide Composites and Their Application in Efficient Removal of Cr(VI)

The organic–inorganic hybrid material of polyaniline/Mg/Al layered double hydroxides (PANI/LDHs) was fabricated through in situ oxidative polymerization. PANI/LDHs were characterized by field emission scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and thermogravimetric analysis. The results showed that PANI was successfully grown on PANI/LDHs. PANI/LDHs were further applied to remove Cr(VI) from aqueous solution, which exhibited outstanding removal capacity toward Cr(VI) (393.70 mg/g), comparable to Cr(VI) removal on PANI nanotubes (198.67 mg/g) and many other materials. The adsorption kinetics followed the pseudo-second-order model. The adsorption of Cr(VI) on PANI/LDHs was highly pH dependent. The Langmuir model described the adsorption isotherm data better than the Freundlich model. Thermodynamic parameters for the adsorption system were calculated and suggested that the adsorption process was spontaneous and endothermic. As a result, this study indicates that PANI/LDHs may be ideal materials for Cr(VI) wastewater treatment.