Manganese Oxide-Based Materials for Adsorption and Removal of Dyes

Original Article:
Removal of dye from polluted water using novel nano manganese oxide-based materials

Md. Aminul Islam, et al.

Journal of Water Process Engineering 32 (2019): 100911.

10.1016/j.jwpe.2019.100911

The presence of dyes in wastewater can cause serious problems for aquatic organisms and humans. So far, there have been many works reported on the use of nano-manganese oxide as a dye adsorbent. They are promising adsorbents for commercial use due to their amorphous nature, high specific surface area (SSA), mesoporous structure, and low to moderate point of zero charge (pH_PZC). In this work, the authors summarize the research progress on the use of nano-manganese oxide adsorbents for the removal of dyes from wastewater.

Common Dyes in Wastewater

Generally, dyes are divided into cationic dyes, anionic dyes and nonionic dyes, common dye examples include:

• Cationic Dyes: methylene blue (MB), crystal violet (CV), brilliant green (BG) and malachite green (MG).
• Anionic Dyes: methyl orange (MO), Congo Red (CR), acid red-b (ARB), Rhodamine-B (RhB), orange green (OG), Prussian red (PR), alizarin red, rose Bengal, basic yellow 28 and pinacyanol chloride.

It has been reported that MnOs has been used as adsorbents to remove MB, MO, RhB, CV, and CR dye molecules in solution.

Dyes Removable by Manganese Oxide

Commonly used manganese adsorbents include hydrated manganese dioxide or birnessite (δ- MnO₂), pyrolusite (β- MnO₂), hausmannite (Mn₃O₄), manganite (MnOOH), cryptomelane (α-MnO₂), Mn₂O₃ and their various composite materials or coatings. Here are just a few examples:

• Methylene blue (MB): There are studies using MnO, bixbyite (α-Mn₂O₃), hausmannite (Mn₃O₄), and birnessite (δ-MnO₂) to treat MB polluted water. The results showed that hausmannite was the most effective MB adsorbent. In the presence of H₂O₂ at 80 °C, an initial MB concentration of 100 mg/L MB can be degraded by hausmannite by 99.3%.
• Malachite green (MG): Porous manganese oxide octahedral molecular sieve (OMS-2) (cryptophyllite phase) nanorods were prepared for the catalytic degradation (5 mg/L) of MG. The results showed that OMS-2 could degrade 99% of the dyes by pseudo-first-order kinetics within 1 h at room temperature.
• Methyl orange (MO): Zhang et al. prepared two composites, such as MnO₂-M and MnO₂/ Mn₃O₄-M, using birnessite (δ- MnO₂), hausmannite (Mn₃O₄) and magnesium (M) wire. They successfully used these composites as oxidants or catalysts to treat MO from wastewater in presence hydrogen peroxide.

• Rhodamine B (RhB): Three different manganese oxides, cryptomelane (α-MnO₂), pyrolusite (β-MnO₂) and birnessite (δ-MnO₂), were used to decolorize RhB solutions. Under the same conditions, different minerals had different decolorization rates, indicating that the decolorization effect of minerals on RhB depended on pH_PZC, crystal type, and solution pH. Cryptomelane exhibited the greatest decolorization ability in the pH range of 2.0-6.0.

Chemicals Related in the Paper:

Catalog Number	Product Name	CAS Number
ACM1317346-1	Manganese Oxide Nanoparticles / Nanopowder	1317-34-6
ACM11129605	Manganese oxide	11129-60-5
ACM12244325	Birnessite(Na4(Mn14O27).9H2O)	12244-32-5
ACM1309553	MANGANESE OXIDE	1309-55-3