Controllable Synthesis of Ca-Mg-Al Layered Double Hydroxides and Calcined Layered Double Oxides for the Efficient Removal of U(VI) from Wastewater Solutions

Abstract

Novel rod-like ternary nanoscale layered double hydroxides (Ca-Mg-Al-LDH) and their bimetal derivatives (Ca-Mg-Al-LDOx, x: 200, 300, 400, 500, and 600 °C) were fabricated with a simple-green hydrothermal and calicination process. The interaction mechanism and adsorption property of U(VI) on Ca-Mg-Al-LDH and Ca-Mg-Al-LDOx were investigated by a batch technique and spectroscopy analysis, and the results indicated that U(VI) could form strong and stable surface complexes on Ca-Mg-Al-LDH and Ca-Mg-Al-LDOx surfaces. The adsorption capacity of U(VI) on various adsorbents could be controlled and adjusted through changing the calcination temperature, which was attributed to the different contents of various metal–oxide bonds (e.g., Ca–O, Mg–O, and Al–O). The adsorption capacities of U(VI) on these adsorbents were in the order of Ca-Mg-Al-LDO500 (486.8 mg/g) > Ca-Mg-Al-LDO600 (373.4 mg/g) > Ca-Mg-Al-LDO400 (292.5 mg/g) > Ca-Mg-Al-LDO300 (260.0 mg/g) > Ca-Mg-Al-LDO200 (223.5 mg/g) > Ca-Mg-Al-LDH (132.5 mg/g), which...