Related Experiment Video

Updated: May 18, 2026

Preparation of Polyoxometalate-based Photo-responsive Membranes for the Photo-activation of Manganese Oxide Catalysts
05:47

Preparation of Polyoxometalate-based Photo-responsive Membranes for the Photo-activation of Manganese Oxide Catalysts

Published on: August 7, 2018

pH-dependent mechanisms of methylene blue reacting with tunneled manganese oxide pyrolusite

Wen-Hui Kuan1, Yen-Chuan Chan

  • 1Department of Safety, Health, and Environmental Engineering, Ming Chi University of Technology, 84 Gung-Juan Road, Taishan 24301, New Taipei City, Taiwan, ROC. whkuan@mail.mcut.edu.tw

Journal of Hazardous Materials
|September 25, 2012
PubMed

Insights

Manganese oxide pyrolusite oxidizes methylene blue (MB) via N-demethylation, forming azure dyes. Pyrolusite acts as an oxidant below pH 4.70 and a catalyst above, with thionin (TH) adsorbing onto its surface.

Area of Science:

  • Environmental Chemistry
  • Materials Science
  • Catalysis

Background:

  • Methylene blue (MB) is a common dye pollutant.
  • Manganese oxides are effective environmental remediation materials.
  • Understanding degradation pathways is crucial for water treatment.

Purpose of the Study:

  • To investigate the oxidative degradation of MB by pyrolusite.
  • To elucidate the role of pH and reaction time in the degradation process.
  • To identify degradation products and their adsorption behavior.

Main Methods:

  • MB degradation experiments were conducted with tunneled manganese oxide pyrolusite.
  • Reactions were analyzed across various pH levels and reaction times.
  • Degradation products were identified, and adsorption onto pyrolusite was studied.

Main Results:

  • MB was degraded via N-demethylation, producing azure B, azure A, azure C, and thionin (TH).
  • Pyrolusite acted as an oxidant below pH 4.70 and a catalyst above this pH.
  • Thionin (TH) was the only compound adsorbed onto pyrolusite, with adsorption increasing with pH.

Conclusions:

  • Tunneled pyrolusite effectively degrades MB through oxidative pathways.
  • The catalytic activity of pyrolusite is enhanced at higher pH due to its surface properties.
  • The study provides insights into the mechanism of MB degradation and pyrolusite's role in water purification.

More Related Videos

[(DPEPhos)(bcp)Cu]PF6: A General and Broadly Applicable Copper-Based Photoredox Catalyst09:12

[(DPEPhos)(bcp)Cu]PF6: A General and Broadly Applicable Copper-Based Photoredox Catalyst

Published on: May 21, 2019

Biofunctionalized Prussian Blue Nanoparticles for Multimodal Molecular Imaging Applications11:28

Biofunctionalized Prussian Blue Nanoparticles for Multimodal Molecular Imaging Applications

Published on: April 28, 2015

Related Concept Videos

Microbes and Other Elemental Cycles01:24

Microbes and Other Elemental Cycles

Microbial activity plays a pivotal role in the biogeochemical cycling of iron and manganese, especially at the redox gradients characteristic of stratified aquatic environments. These cycles are driven by microbial transformations between oxidized and reduced forms of the metals, allowing organisms to exploit them for metabolic energy and structural purposes.Iron Cycling Across Redox GradientsIn neutral, oxygen-rich surface waters, iron is predominantly found in its oxidized, insoluble ferric...
Phase II Reactions: Methylation Reactions01:17

Phase II Reactions: Methylation Reactions

Methylation is a phase II biotransformation process involving the attachment of a methyl group to a substrate. Enzymes known as methyltransferases orchestrate this reaction.
The mechanism of methylation unfolds in two stages. The first stage sees a methyltransferase enzyme facilitating the transfer of a methyl group from S-adenosylmethionine (SAM) to the substrate, forming S-adenosylhomocysteine (SAH). The second stage involves further metabolism of SAH into homocysteine, which can be recycled...
Acid Mine Drainage01:19

Acid Mine Drainage

Mining activities that disturb sulfide-rich rocks, particularly those containing pyrite (FeS₂), initiate a cascade of geochemical and microbiological processes with serious environmental implications. When exposed to air and water, pyrite undergoes oxidation, releasing sulfate, ultimately forming sulfuric acid and mobilizing heavy metals into surrounding water systems. This phenomenon, known as acid mine drainage (AMD), results in low pH waters laden with toxic elements that threaten aquatic...
Radical Oxidation of Allylic and Benzylic Alcohols01:21

Radical Oxidation of Allylic and Benzylic Alcohols

Activated manganese(IV) oxide can selectively oxidize allylic and benzylic alcohols via a radical intermediate mechanism. Primary allylic alcohols are oxidized to aldehydes, while secondary allylic alcohols yield ketones. The redox reaction of potassium permanganate with an Mn(II) salt such as manganese sulfate (under either alkaline or acidic conditions), followed by thorough drying, yields the oxidizing agent: activated MnO2. While MnO2 is insoluble in the solvents used for the reaction, the...
Colors and Magnetism03:02

Colors and Magnetism

Color in Coordination Complexes
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human eye.