Simple construction of core–shell MnO2@TiO2 with highly enhanced U(vi) adsorption performance and evaluated adsorption mechanism

Abstract

The adsorption remediation of radioactive contamination from wastewater is scientifically and economically important. In this work, titanium dioxide-modified manganese dioxide (MnO₂@TiO₂) was prepared by immobilizing crystalline anatase titanium dioxide (TiO₂) on the surface of alpha manganese dioxide nanowire (MnO₂). The base material MnO₂ nanowire acted as a physical template for the guest TiO₂, and the formed MnO₂@TiO₂ composite exhibited a highly uniform core–shell nanorod structure. The MnO₂@TiO₂ composite was investigated as an efficient adsorbent for the removal of U(VI) from aqueous solution. In the same system, MnO₂@TiO₂ exhibited a much higher maximum adsorption capacity (105.3 mg g⁻¹) for U(VI) as compared with MnO₂ (13.3 mg g⁻¹), showing that the performance of the surface-modified MnO₂ was greatly improved. The fitting results for kinetic and isothermal models manifested that U(VI) ion adsorption by MnO₂@TiO₂ involved monolayer chemisorption. Characterization before and after adsorption was performed and the results compared and analyzed carefully, with the conclusion that there might be three kinds of interactions between U(VI) and MnO₂@TiO₂ during the adsorption process, namely inner-sphere surface complexation, chemical precipitation, and electrostatic interaction. The low-cost, facile fabrication method and efficient performance endow the adsorbent MnO₂@TiO₂ with a high potential for U(VI) removal from actual wastewater.