Controllable ZnO architectures with the assistance of ethanolamine and their application for removing divalent heavy metals (Cu, Pb, Ni) from water

Abstract

Controllable ZnO architectures were synthesized via a facile hydrothermal or solvothermal method with the help of ethanolamine, and without any addition of templates. It was found that the molar ratio between Zn(OAc)₂ and NaOH, and the polarity of the solvent have a great impact on the formation of flowerlike, rodlike, and spherical ZnO architectures. The as-prepared ZnO may be used to remove divalent heavy metals (Cu²⁺, Ni²⁺, and Pb²⁺) from aqueous solution, and the concentration of heavy metals was monitored by an atomic adsorption spectrometer. The adsorption kinetics were well fitted to a pseudo-second order model, even if the structures of ZnO were different from each other. The equilibrium adsorption data for Cu²⁺, Ni²⁺, and Pb²⁺ were consistent with the Langmuir, Freundlich, and Langmuir isotherms, respectively. It should be mentioned that the adsorption capacity of ZnO products for removing various divalent heavy metals decreased as follows: Pb²⁺ > Cu²⁺ > Ni²⁺, and the order of adsorption capacity of ZnO with different morphologies can be calculated to be spherical ZnO > rodlike ZnO > flowerlike ZnO > commercial ZnO for the given heavy metal ions.