Hierarchical Mg/Al hydrotalcite oxide hollow microspheres with excellent adsorption capability towards Congo red

A novel citrate anion-intercalated Mg/Al layered double hydroxide (CA-LDH) is synthesized via a one-step hydrothermal process. The synthesized CA-LDH is a hollow flower-like microsphere composed of thin nanoflakes (10 nm in thickness). After calcination, the formed Mg/Al layered double oxide (CA-LDO) hollow microspheres possess a high specific surface area of 247.8 m² g^-1 and a high pore volume of 0.97 cm³ g^-1, which endow them with excellent adsorption ability towards Congo red (CR). The maximum adsorption capacity of CR onto CA-LDO can reach up to 1883 mg g^-1. The significantly improved adsorption capacity of CA-LDO can be attributed to its unique structures of hierarchical hollow microspheres, in which the hierarchical porous shell layer provides enough adsorption sites to anchor the dye molecules, and the hollow core can preserve the absorbed dye. This study provides a promising novel adsorbent which can be used for efficient water remediation.