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Environmental Engineering Research 2008;13(3): 131-135. DOI: https://doi.org/10.4491/eer.2008.13.3.131
Application of Ferrate(VI) on the Decomplexation of Cu(II)-EDTA
Diwakar Tiwari1, Jae-Kyu Yang2, Yoon-Young Chang3, and Seung-Mok Lee4
1Department of Chemistry, Mizoram University, Aizawl, India
2Division of General Education, Kwangwoon University, Seoul, Korea
3Department of Environmental Engineering, Kwangwoon University, Seoul, Korea
4Department of Environmental Engineering, Kwandong University, Gangneung, Korea
Corresponding Author: Seung-Mok Lee ,Tel: +82-33-649-7535, Fax: +82-33-642-7635, Email: leesm@kd.ac.kr
Received: March 11, 2008;  Accepted: May 11, 2008.
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In this study, Fe(VI) was employed as a multi-functional agent to treat the simulated industrial wastewater contaminated with Cu(II)-EDTA through oxidation of EDTA, decomplexation of Cu(II)-EDTA and subsequent removal of free copper through precipitation. The decomplexation of 10-4 M Cu(II)-EDTA species was performed as a function of pH at excess concentration of Fe(VI). It was noted that the acidic conditions favor the decomplexation of Cu(II)-EDTA as the decomplxation was almost 100% up to pH 6.5, while it was only 35% at pH 9.9. The enhanced degradation of Cu(II)-EDTA with decreasing the pH could be explained by the different speciation of Fe(VI). HFeO4 - and H2FeO4, which are relatively more reactive than the unprotonated species FeO4 2-, are predominant species below neutral pH. It was noted that the decomplexation reaction is extremely fast and within 5 to10 min of contact, 100% of Cu(II)-EDTA was decomplexed at pH 4.0. However, at higher pH (i.e., pH 10.0) the decomplexation process was relatively slow and it was observed that even after 180 min of contact, maximum ca 37% of Cu(II)-EDTA was decomplexed. In order to discuss the kinetics of the decomplexation of Cu(II)-EDTA, the data was slightly fitted better for the second order rate reaction than the first order rate reaction in the excess of Fe(VI) concentration. On the other hand, the removal efficiency of free Cu(II) ions was also obtained at pH 4.0 and 10.0. It was probably removed through adsorption/coagulation with the reduced iron i.e., Fe(III). The removal of total Cu(II) was rapid at pH 4.0 whereas, it was slow at pH 10.0. Although the decomplexation was 100% at lower pH, the removal of free Cu(II) was relatively slow. This result may be explicable due to the reason that at lower pH values the adsorption/coagulation capacity of Fe(III) is greatly retarded. On the other hand, at higher pH values the decomplexation of Cu(II)-EDTA was partial, hence, slower Cu(II) removal was occurred.
Keywords: Fe(VI) | Cu(II)-EDTA | Decomplexation | Kinetics | Oxidation
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