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 (62.64 m2/g), MnO2-110 depicted the best Sr2+ adsorption performance with maximum adsorption capacity of 52 mg/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 (∼ 10 min) and is capable to bind Sr2+ in slightly acidic to alkaline solutions.