Decomposition of the Methylene Blue Dye Using Layered Manganese Oxide Materials Synthesized by Solid State Reactions

Abstract

The modulation in the synthesis parameters of layered manganese oxides allowed us to produce materials with different AC conductivities. These conductivities were correlated with the catalytic performance of the materials in the decomposition of methylene blue, as a model of electron transfer reactions. The manganese oxides were prepared by thermal reduction of KMnO4 at 400°C and 800°C where one sample was heated at 1°C/min and the other was heated at 10°C/min. The materials were characterized by atomic absorption, average oxidation states of manganese, X-ray diffraction, thermogravimetric analysis, and scanning electron microscopy. The results indicate that, by increasing the synthesis temperature, both the lamellar arrangement and the crystal size increased, while the Mn4+ amount in the material decreased. Furthermore, it was observed that as the conductivity increases for the materials, the catalytic performance also increases. Therefore, a direct correlation between the conductivity and catalytic performance can be established. For example, the layered manganese oxides material synthesized at 400°C, using a heating rate of 10°C/min, showed the highest AC conductivity and had the best performance in the degradation of methylene blue. Finally, we propose a general mechanism for understanding how manganese oxides behave as catalysts that produce oxidizing species from H2O2 which degrades methylene blue. Our proposed mechanism takes into consideration the state of aggregation of the catalyst, the availability of Mn4+, and the electrical conductivity.

The Effect of pH and Buffer on Oligonucleotide Affinity for Iron Oxide Nanoparticles

“…ROS production highly depends on the nanoparticles' size, distribution, stability, and surface modification. For this reason, synthesized MNPs were tested in the methylene blue (MB) discoloration assay using frequently used oxidizing agent hydrogen peroxide [53][54][55]. ROS generated from the reaction of iron ions with hydrogen peroxide will degrade MB into colorless products.…”

Water hyacinth plant extract mediated green synthesis of Cr2O3/ZnO composite photocatalyst for the degradation of organic dye

“…OH) will be formed. Then, · OH and · O 2 - could be reacted with MB dye and decomposition of the organic dye in to H 2 O and CO 2 is expected [ 58 , 59 ]. Therefore, Cr 2 O 3 /ZnO composite catalytic efficiency could be improved due to lowering the electron-hole pair recombination rates resulted from p–n heterojunction formation and the catalyst porosity due to the presence of Eichhornia crassipes plant extract in the preparation.…”

Preparation of Manganese Dioxide Nanoparticles on Laterite for Methylene Blue Degradation

“…e effect of the amount of the laterite after MnO 2 NP (M2) catalyst coating on the removal of methylene blue is investigated and is shown in Figure 10 and Table S6 (Supplementary materials). e result shows that the degradation efficiency increases with increasing catalyst content, due to the increase in the catalytic active sites on the surface of the catalyst and the associated generated free hydroxyl radicals (equations (9)-(12)) [29,30]. Especially, the degradation efficiency increases rapidly in the range of 0.5 to 1.5 g of M2 ( Figure 10):…”