Template-Free Synthesis of ZnNiAl-LDH and LDO Microspheres for Adsorption of Methyl Orange

ZnNiAl-layered double hydroxide (ZnNiAl-LDH) microspheres were synthesized using a facile hydrothermal method without any templates. After being calcined, ZnNiAl-layered double oxide (ZnNiAl-LDO) micropheres were obtained. The as-prepared samples were used as adsorbents to remove of methyl orange (MO) from aqueous solution. Results show the adsorption kinetics and isotherms can be fitted well with the pseudo-second-ordered and Langmuir models for both adsorbents. ZnNiAl-LDO has higher adsorption capacity, faster adsorption rate and better recyclability than ZnNiAl-LDH. The maximum capacity for ZnNiAl-LDO is 1226.84 mg g –1 at 298 K. After five adsorption-desorption cycles, the removal efficiency of ZnNiAl-LDO still retains at 98.1%. The adsorption mechanisms for ZnNiAl-LDH are attributed to ion exchange, electrostatic interaction and accompanied by surface complexation. Excepting for above, the structure reconstruction and hydrogen bond also play a part in the adsorption of MO onto ZnNiAl-LDO.