Shape-controlled synthesis of Mn3O4 nanocrystals and their catalysis of the degradation of methylene blue

Abstract

Various sizes and shapes of Mn 3 O 4 nanocrystals have been prepared in a one-pot synthesis in extremely dilute solution by soft template self-assembly. To better control size and shape, the effects of varying the growth time, reaction temperature, surfactant, and manganese source were examined. The average size of octahedral Mn 3 O 4 crystallites was found to be related to the reaction time, while higher reaction temperature (150 °C ) and the use of a cetyltrimethylammonium bromide/poly(vinylpyrrolidone) (CTAB/PVP) mixture allowed construction of a better-defined octahedral morphologies. When PVP or poly(ethylene oxide)-poly(propylene oxide) (P123) was used as template, large-scale agglomeration resulting in loss of the octahedral morphology occurred and crystallites with a quasi-spherical shape were obtained. The nano-octahedral crystallites were shown to be an efficient catalyst for the oxidation of methylene blue.

Oxidative Degradation of Methylene Blue Using Mn3O4 Nanoparticles

“…In the spectrum, the characteristic peak of MB at 664 was found which is in good agreement with the reported earlier values [31]. As the reaction time was prolonged, the reaction solution gradually turned colorless and the original absorption maximum at 664 nm was gradually decreased and shifted to shorter wavelength [17,18] indicating that MB was oxidized by Mn 3 O 4 . Zaied et al (2011) found the presence of intermediate reaction products, azure A (AA), azure B (AB), azure C (AC), and thionine (Th) during the degradation of MB using manganese oxide and the corresponding characteristic UV-vis λ max was identified as 628, 638, 618, and 601 nm, respectively [32].…”

“…It can be seen from the result that at medium pH greater than 4 (higher than that of pH pzc ), MB was not oxidized by Mn 3 O 4 [34]. Moreover, in neutral and alkali media, there was hardly any decolorization of MB [17,18].…”

“…In the present study, methylene blue (MB) was chosen as a model of organic contaminants as it is the most commonly used dye in the textile industry [15] that can result in permanent burns to the eyes of humans and animals, nausea, vomiting, profuse sweating, mental confusion, and methemoglobinemia [16]. The decolorization of MB using Mn 3 O 4 was studied by a number of workers [17,18]; however, the mechanism of decolorization is not well evident. As a result, a detailed mechanism of the MB decolorization by Mn 3 O 4 is inevitable.…”

Dependency of tunable microwave absorption performance on morphology-controlled hierarchical shells for core-shell Fe3O4@MnO2 composite microspheres

“…The specific surface area and porosity of three different Fe 3 O 4 @MnO 2 composite microspheres were determined by N 2 adsorption-desorption isotherms shown in the Figure 6. According to the IUPAC classification, all of three graphics display a type IV isotherm with a H3-type hysteresis loop (P/P 0 ＞ 0.4), indicating the formation of pores [34]. Moreover, the sharp increment of N 2 adsorption amount on the three isotherms at the relative pressure P/P 0 = 0.92-1.0 demonstrates the existence of macroporosity.…”

Synthesis of Magnetic Carbon Supported Manganese Catalysts for Phenol Oxidation by Activation of Peroxymonosulfate

“…Compared with traditional separation technologies such as centrifugation and filtration, magnetic separation through an external magnetic field is more convenient and less cost-intensive [16]. Magnetite (Fe 3 O 4 ) nanoparticles are prevalently employed as magnetic cores owing to their outstanding magnetic and electrochemical properties [17][18][19][20]. However, their high surface area to volume ratio and strong dipole-dipole attraction make them prone to aggregation, and the limited functional groups circumvent their further applications [16].…”