α/γ-氧化铝对合成镁铝水滑石结构性能的影响

Effect of α/γ-alumina on structure and properties of synthesized Mg-Al hydrotalcite

为了解α-氧化铝和γ-氧化铝合成镁铝水滑石(LDH)结构性能的差异,以α-氧化铝和γ-氧化铝为原料采用水热法合成了镁铝水滑石α-LDH-2.0和γ-LDH-2.0。通过扫描电镜(SEM)、红外光谱(FT-IR)、拉曼光谱(Raman)、X射线光电子能谱(XPS)、X射线衍射(XRD)、热重分析(TG-DTG)等对α-LDH-2.0和γ-LDH-2.0进行了检测,并将α-LDH-2.0和γ-LDH-2.0用于吸附刚果红的实验。结果表明:γ-氧化铝合成的γ-LDH-2.0板层更无序、结晶度较高,吸附实验中γ-LDH-2.0对刚果红的吸附效果强于α-LDH-2.0,并且适应更广的溶液pH范围,说明使用不同晶型的氧化铝可以调控镁铝水滑石的形貌结构使其高效吸附刚果红。当刚果红质量浓度为100 mg/L、镁铝水滑石添加量为20 mg时,α-LDH-2.0和γ-LDH-2.0对刚果红的吸附量较大,酸性条件更有利于α-LDH-2.0和γ-LDH-2.0对刚果红的吸附,α-LDH-2.0和γ-LDH-2.0去除刚果红的吸附动力学更符合拟二级动力学方程,等温吸附过程符合Langmuir模型。

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 usingα/γ-alumina(α-Al_(2)O_(3)/γ-Al_(2)O_(3))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(TGDTG),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-Al_(2)O_(3) 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 Al_(2)O_(3) 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 forα-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.