A waxberry-like SiO2@MnSiO3 core–shell nanocomposite synthesized via a simple solvothermal self-template method and its potential in catalytic degradation and heavy metal ion removal

Abstract

A novel waxberry-like SiO₂@MnSiO₃ core–shell nanocomposite was facilely fabricated via the simple one-step thermal treatment of SiO₂ nanospheres, MnCl₂·4H₂O, ethylenediamine (EDA), and ethylene glycol (EG). Through an intensive investigation of the effects of Si/Mn molar ratio and reaction time on the grain growth characteristics, a self-template growth mechanism of SiO₂@MnSiO₃ was proposed. The self-template silica nanospheres released silicate anions slowly from their surfaces by alkali etching in the presence of EDA, and a fast precipitation reaction between Mn²⁺ cations and silicate anions occurred within the interfacial regions, eventually leading to the formation of a MnSiO₃ shell on the surfaces of silica nanospheres. A well-defined waxberry-like SiO₂@MnSiO₃ nanostructure was obtained with a Si/Mn molar ratio of 5 : 1 and a reaction time of 10 h according to our experiments. Interestingly, this SiO₂@MnSiO₃ exhibited a high catalytic activity for oxidative degradation of methylene blue (MB); more than 93% of MB could be decomposed within 40 min. Moreover, it could also act as a potential adsorbent for efficient removal of Pb²⁺ ions from aqueous solution. The Pb²⁺ adsorption capacity was up to 50.5 mg g⁻¹, which was significantly higher than those found for many other conventional adsorbents. Overall, this work not only provides a new insight into the fabrication of silica-supported MnSiO₃ nanocomposites but also demonstrates their excellent performance in heterogeneous catalysis and adsorption.