| Treatment and disposal of dye wastewater has become one of the important fields in the environment problems around the world, due to that the dyes wastewater is highly colored, discharged wildly, harmful and hard to be biodegraded. Developing low-cost methods with highly efficiency and widely applied have gained more and more concerns. In this study, a simple, high catalytic efficiency new Fenton-like system was build in which simple irons (cobalt and copper) can activate H2O2 in bicarbonate aqueous solutions for the removal of dye pollutants. That is the metal ions (Co2+ and Cu2+)-sodium bicarbonate-hydrogen peroxide system. Some innovative conclusions were got by discussions of the construction of Fenton-like system, the degradation behavior?influence factors and the interactions of each species in system, the mechanism of dye degradation, which were systematically researched in this paper respectively.(1) Co2+-HC03--H2O2 was investigated as an effective system for the degradation of the dyes during which the role of Co2+?HCO3-?H2O2 are indispensable. Complete decolorization of 50 ?M AOII was observed with 5 ?M Co2+ ions and 4 mM H2O2 in 10 mM NaHCO3 aqueous solution after 10 min, which was much faster than that of Fenton reagent with 50 ?M Fe2+ ions. The system was also useful for some other dyes degradation such as Reactive brilliant red, Sulforhodamine B, Methyl Orange, Methylene blue and Rhodamine B. Besides, In the presence of other pollutants such as methylene blue, SulforhodamineB or a significant amount of anions including Cl-? CO32-, SO42-, NO3-, HPO42- and CH3COO-, AOII was still rapidly degraded(2) The tightly associated hydroxyl radicals with the cobalt complex were investigated as the reactive species for AOII degradation in the Co2+-HCO3--H2O2 system. Co2+ can be oxidated to Co3+ firstly, and then partly of the Co3+ can be reduced to Co2+.(3) It can be concluded that the contemporaneous cleavage of the two C-N bonds of AOII by the Co2+-HCO3--H2O2 system led to decolorization of the dye with the formation N2,p-PSA and 1,2-naphthaquinone, a possible pathway of dye degradation was proposed in details.(4) Cu2+-HCO3--H2O2 was also proved to be an effective system for the degradation of the AOII as well as MO, MR and TB. The formed copper (II) species at different HCO3- concentrations were calculated. The study of the interaction among the Cu2+-HCO3--H2O2 system indicated that Cu2+ can form different complexes with HCO3- showed a new absorption peak at 270nm in the UV area.(5) The radical scavenging measurements further implied that the produced higher oxidation state of copper, Cu (?) was to be responsible for the dye decolorization. With the addition of H2O2, the valence of Cu2+ was supposed to change in the Cu2+-HCO3-solution, the amount of formed Cu(?) within 60min was suggested to be 13% according to the amount calculation of Cu(?) and Cu(?). The contemporaneous cleavage of the two C-N bonds of AOII by the Cu2+-HCO3--H2O2 system led to dye degradation with the formation of N2, p-PSA,1,2-naphthaquinone and its further oxidation product.(6) The kinetics studies of formed Cu(?) was also investigated. It shows that the higher concentrations of hydrogen peroxide, the higher rate of the reactions. But when it comes to 50mM, the rate almost does not increase. For the different concentration of sodium bicarbonate, it first increased and then decreased with the maximum value obtained at 5mM HCO3-. |
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