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pH-dependent mechanisms of methylene blue reacting with tunneled manganese oxide pyrolusite
- Source :
- Journal of Hazardous Materials. :152-159
- Publication Year :
- 2012
- Publisher :
- Elsevier BV, 2012.
-
Abstract
- This study examined the reaction of methylene blue (MB) with tunneled manganese oxide pyrolusite regarding pH and reaction time. MB was cleaved through N-demethylation, in which reaction azure B (AB), azure A (AA), azure C (AC), and thionin (TH) were stepwise generated at all tested pH. Pyrolusite predominantly serves as the oxidant in the oxidative degradation of MB at a pH under the pHiep of pyrolusite (4.70) while playing the role of the catalyst at pH higher than pHiep. Among all oxidative products and original MB molecule, TH is the alone compound adsorbed onto the pyrolusite surface at all tested pH. However, the quantity of adsorbed TH increases with pH because of the stronger affinity between the cationic TH molecule and the more negatively charged surface of pyrolusite with pH increasing. Because the lattice oxygen and surface hydroxyl groups form excited oxygen firstly to cause the oxidation of MB, the tunneled pyrolusite with less constrained corner and edge oxygen catalytically promote the oxidation reaction at pH beyond pHiep. The vacancy of the consumed lattice oxygen forms the active sites for the other oxidation and could be replenished by molecular oxygen to complete a catalytic cycle.
- Subjects :
- Environmental Engineering
Health, Toxicology and Mutagenesis
Inorganic chemistry
chemistry.chemical_element
Azure A
engineering.material
Oxygen
Redox
Catalysis
Water Purification
chemistry.chemical_compound
Adsorption
Environmental Chemistry
Coloring Agents
Waste Management and Disposal
Pyrolusite
Chemistry
Oxides
Hydrogen-Ion Concentration
Pollution
Methylene Blue
Manganese Compounds
Catalytic cycle
engineering
Oxidation-Reduction
Water Pollutants, Chemical
Methylene blue
Subjects
Details
- ISSN :
- 03043894
- Database :
- OpenAIRE
- Journal :
- Journal of Hazardous Materials
- Accession number :
- edsair.doi.dedup.....2d37188c34976463f3a8d03cba7d32e0