Morphology controlled facile synthesis of MnO2 adsorbents for rapid strontium removal

Abstract

MnO2 nanostructures with three distinct architectures, namely flower, balk and tube-like, have been synthesized through a single step microwave assisted hydrothermal method at different reaction temperatures (110°C, 140°C and 180°C). The characterization of as prepared MnO2 samples were performed by means of Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The N2 adsorption–desorption isotherms revealed the higher specific surface area and porosity of the flower like MnO2 as compared to balk and tube-like MnO2. The adsorption behavior of as prepared adsorbents was investigated towards Sr2+ radionuclide. Because of the hierarchal structure and the high surface area (62.64m2/g), MnO2-110 depicted the best Sr2+ adsorption performance with maximum adsorption capacity of 52mg/g at pH 6 as compared to other MnO2 morphologies synthesized at 140°C and 180°C. The kinetic studies revealed that the adsorption of Sr2+ onto MnO2-110 followed the pseudo-first-order model whereas the adsorption equilibrium data obeyed the Freundlich and Sips model. Moreover, the MnO2-110 adsorbent reached the steady state quickly (∼10min) and is capable to bind Sr2+ in slightly acidic to alkaline solutions.