Decolorization of methylene blue by delta-MnO2-coated montmorillonite complexes: emphasizing redox reactivity of Mn-oxide coatings.
Delta-MnO(2) coatings on clay substrates tend to be poorer in crystallinity as compared with their discrete counterparts, which may be of environmental significance for adsorption and oxidation of contaminants. Discrete delta-MnO(2) particles and three delta-MnO(2)-coated montmorillonite complexes with varying MnO(2) loadings (4.8-34.9%) were synthesized, and oxidative decolorization of methylene blue (MB) by the synthetic materials was investigated in batch systems. Results showed that oxidative decolorization of MB increased with increasing loading of Mn-oxide coatings, whereas oxidation capacity of the coatings, on the basis of unit mass of MnO(2), tended to decrease. Initial reaction rate of MB oxidation by both delta-MnO(2) coatings and their discrete counterpart increased linearly with increasing Mn-oxide loadings, but the rate of the former was higher than that of the latter. An increase in humic acid concentration displayed a progressively enhanced promotive effect on MB decolorization, whereas the promotive effect was greatly suppressed at lower pH.
Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, College of Chemistry and Chemical Engineering, Ocean University of China, Shandong Province, Qingdao, China. zhumaoxu@ouc.edu.cn
Mao-Xu
MX
Zhu
Zheng
Z
Wang
Shao-Hui
SH
Xu
Tie
T
Li
D000327:Adsorption; D001546:Bentonite / Q000737:chemistry*; D003116:Color; D004787:Environmental Pollution / Q000517:prevention & control; D052918:Environmental Restoration and Remediation / Q000379:methods*; D006812:Humic Substances; D006863:Hydrogen-Ion Concentration; D017895:Manganese Compounds / Q000737:chemistry*; D008751:Methylene Blue / Q000737:chemistry*; D010084:Oxidation-Reduction; D010087:Oxides / Q000737:chemistry*
D006812:Humic Substances; D017895:Manganese Compounds; D010087:Oxides; D001546:Bentonite; D008751:Methylene Blue; C016552:manganese dioxide