Decolorization of dye pollutions by manganese complexes with rigid cross-bridged cyclam ligands and its mechanistic investigations.
Exploring pH-insuspensible catalysts for pollutant treatments is still a challenge because of the pH-dependent catalyst stability. A recently developed manganese complex, Mn(Me2EBC)Cl2, (Me2EBC: 4,11-dimethyl-1,4,8,11-tetraazabicyclo[6.6.2]hexadecane) was investigated to decolorize dyes in the pH range of 1-13 using H2O2 as the oxidant, and its stability in service was examined by periodically adding fresh dye and oxidant. The results display that this manganese complex is capable of decoloring dye in both acid and base and keeping activity for a long service period. In addition, its modified analogue, Mn(Et2EBC)Cl2, can perform efficient decolorization in the whole pH range from pH 1 to 13. Combinatorial methods including stoichiometric treatments of dye with freshly synthetic manganese(IV) complex, utilization of radical scavenger, and intermediate analysis by UV-visible spectrophotometry were applied for its mechanistic studies, and a manganese(IV) hydroperoxide intermediate has been suspected to serve as the key active species in decolorization.
Xu
Aihua
A
School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan 430074, China.
Xiong
Hui
H
Yin
Guochuan
G
D001673:Biodegradation, Environmental; D004396:Coloring Agents / Q000737:chemistry*; D006571:Heterocyclic Compounds / Q000737:chemistry*; D006861:Hydrogen Peroxide / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008024:Ligands; D008345:Manganese / Q000737:chemistry*; D009942:Organometallic Compounds / Q000737:chemistry*; D016877:Oxidants / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet
D004396:Coloring Agents; D006571:Heterocyclic Compounds; D008024:Ligands; D009942:Organometallic Compounds; D016877:Oxidants; C024560:cyclam; D008345:Manganese; D006861:Hydrogen Peroxide