Abstract:

To understand the difference in structure and performance of synthetic hydrotalcite，Mg/Al-LDH（α-LDH-2.0/γ-LDH-2.0） was synthesized by hydrothermal synthesis method by using α/γ-alumina（α-Al₂O₃/γ-Al₂O₃） as raw materials.α-LDH-2.0 and γ-LDH-2.0 were characterized by scanning electron microscopy（SEM），infrared spectroscopy（FT-IR），Raman spectroscopy（Raman），X-ray photoelectron spectroscopy（XPS），X-ray diffraction（XRD），thermogravimetry（TG-DTG），etc.α-LDH-2.0 and γ-LDH-2.0 were used for adsorption experiments of Congo red.The results showed that γ-LDH-2.0 synthesized by γ-Al₂O₃ plate layer was more disordered and had higher crystallinity.In the experiment，it was found that the adsorption effect of γ-LDH-2.0 on Congo red was better than that of α-LDH-2.0 and was suitable for a wider range of environmental pH，indicating that the morphology and structure of hydrotalcite could be controlled by the crystal form of Al₂O₃ to make it adsorb Congo red efficiently.When the concentration of Congo red was 100 mg/L and the addition amount of hydrotalcite was 20 mg，the unit adsorption capacity of hydrotalcite to Congo red was larger，and the acidic conditions were more conducive for α-LDH-2.0 and γ-LDH-2.0 to the adsorption of Congo red.The adsorption kinetics of α-LDH-2.0/γ-LDH-2.0 except Congo red was more in line with the pseudo-second-order adsorption kinetic equation，and the isotherm adsorption process was in line with the Langmuir model.

Key words: α-Al₂O₃, γ-Al₂O₃, LDH, Congo red, adsorption