Novel approach for the synthesis of Mg(OH)₂ nanosheets and lamellar MgO nanostructures and their ultra-high adsorption capacity for Congo red

A phase transfer method was developed to prepare Mg(OH)2nanosheets and a subsequent adsorption–calcination process was followed to obtain lamellar MgO nanostructures. The as-prepared MgO nanosheets also showed a superior adsorption property of Congo red. Transmission electron microscopy and x-ray diffractometer results indicated that the as-obtained Mg(OH)2was plate-shaped with a hexagonal crystal structure where MgO possessed a lamellar structure with a cubic phase. The maximum adsorption capacities of Mg(OH)2and MgO were reached up to 1820 and 2650 mg g−1, respectively. The high adsorption capacity might be related to the particle geometry and large surface area (87.97 m2g−1for Mg(OH)2and 132.31 m2g−1for MgO). The adsorbents can be easily regenerated for five times without any significant loss in their adsorption property. The adsorption behaviors of the Mg(OH)2and MgO adsorbents showed that the adsorption kinetics and isotherms were in good agreement with pseudo-second-order rate equation and Freundlich adsorption model.