Synthesis of Three-Dimensional Hierarchical Flower-Like Mg–Al Layered Double Hydroxides with Excellent Adsorption Performance for Organic Anionic Dyes

In this work, a facile and effective strategy to prepare three-dimensional (3D) hierarchical flower-like Mg–Al layered double hydroxides (3D-LDH) was developed via a one-step double-drop coprecipitation method using γ-Al 2 O 3 particles as a template. The characterization and experimental results showed that the calcined product, 3D-LDO, features a large specific surface area of 204.2 m 2 /g, abundant active sites, and excellent adsorption performance for Congo red (CR), methyl orange (MO), and methyl blue (MB). The maximum adsorption capacities of 3D-LDO for CR, MO, and MB were 1428.6, 476.2, and 1666.7 mg/g, respectively; such performance is superior to that of most reported adsorbents. The adsorption mechanism of organic anionic dyes by 3D-LDO was extensively investigated and attributed to surface adsorption, the memory effect of 3D-LDO, and the unique 3D hierarchical flower-like structure of the adsorbent. Recycling performance tests revealed that 3D-LDO has satisfactory reusability for the three organic anionic dyes.