Photocatalytic degradation of polluted water by means of minerals, such as clays and oxides, which have surfaces that exhibit catalytic properties, has been suggested to be a useful new strategy to promote both organic and inorganic pollutant degradation. Nevertheless, much still remains to be studied about the capability of mixed metal oxides derived from lanthanum-containing layered double hydroxides to promote pollutant removal by means of photocatalytic degradation with the mineral surfaces. The objective of the present study was to investigate the synthesis of ternary MgAlLa mixed-metal oxides (MgAlLa-M) with various Mg/Al/La molar ratios through a hydrotalcite-like precursor route by co-precipitation of appropriate amounts of metal salts from homogeneous solution, followed by calcination at 600°C. The crystal structure, surface morphology, and optical properties of the samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and UV-Vis diffuse reflectance spectroscopy (DRS). Analysis by XRD showed that MgO, La2O3, MgAl2O4, and La10Al4O21 phases coexisted in calcined samples as MgAlLa-M. The samples showed a small band gap of 3.11–3.35 eV according to DRS. The photocatalytic activities of the samples were evaluated by degradation of methylene blue (MB) under visible light irradiation. MgAlLa-M had better photocatalytic properties than hydrotalcite precursors, and the MgAlLa-0.5-M possessed the best photocatalytic activity. The photocatalytic degradation efficiency of MB dye with MgAlLa-0.5-M under visible light irradiation for 1 h was 99.89% in the presence of H2O2, which exceeded the binary MgAl-M (84.06%) under the same conditions. The high photocatalytic activity of the sample was attributed to the addition of La(III). In addition, the possible mechanism of photocatalytic degradation of MB by MgAlLa-M was discussed. The results showed that •O2– plays a major role in the MgAlLa-0.5-M/H2O2 system.

中文翻译：

---

层状双氢氧化物衍生的含 La 混合金属氧化物在 H2O2 存在下降解亚甲蓝的光催化活性

通过矿物（如粘土和氧化物）对污水进行光催化降解，其表面具有催化性能，已被认为是促进有机和无机污染物降解的有用新策略。然而，关于源自含镧层状双氢氧化物的混合金属氧化物通过矿物表面的光催化降解促进污染物去除的能力仍有许多有待研究。本研究的目的是通过类水滑石前驱体途径，通过共沉淀适量的金属盐，研究不同 Mg/Al/La 摩尔比的三元 MgAlLa 混合金属氧化物 (MgAlLa-M) 的合成。均匀溶液，然后在 600°C 下煅烧。晶体结构、表面形貌、通过X射线衍射（XRD）、扫描电子显微镜（SEM）、傅里叶变换红外光谱（FTIR）和紫外-可见漫反射光谱（DRS）对样品的光学性质进行表征。XRD 分析表明，MgO、La2O3、MgAl2O4 和 La10Al4O21 相以 MgAlLa-M 的形式共存于煅烧样品中。根据 DRS，样品显示出 3.11-3.35 eV 的小带隙。通过在可见光照射下降解亚甲蓝 (MB) 来评估样品的光催化活性。MgAlLa-M 比水滑石前驱体具有更好的光催化性能，其中 MgAlLa-0.5-M 具有最好的光催化活性。在 H2O2 存在下，MgAlLa-0.5-M 对 MB 染料的光催化降解效率在可见光照射下 1 h 为 99.89%，超过二元 MgAl-M（84. 06%）在相同条件下。样品的高光催化活性归因于 La(III) 的添加。此外，讨论了MgAlLa-M光催化降解MB的可能机制。结果表明•O2– 在MgAlLa-0.5-M/H2O2 体系中起主要作用。