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Application of Ferrate(4) on the Decomplexation of Cu(2)-EDTA
Diwakar Tiwari,Jae Kyu Yang,Yoon Young Chang,Seung Mok Lee 대한환경공학회 2008 Environmental Engineering Research Vol.13 No.3
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<sup>2-</sup>, 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.
Ferrate(VI): A green chemical for the oxidation of cyanide in aqueous/waste solutions
Tiwari, Diwakar,Kim, Hyoung-Uk,Choi, Bong-Jong,Lee, Seung-Mok,Kwon, Oh-Heung,Choi, Kyu-Man,Yang, Jae-Kyu Taylor Francis 2007 Journal of Environmental Science and Health. Part Vol.42 No.6
<P> The higher oxidation state of iron, i.e. Fe(VI), was employed for the oxidation of the important toxic ion cyanide in aqueous/waste waters. Cyanide was oxidized to cyanate, which is 1,000 times less toxic than cyanide, and can often be accepted for its ultimate disposal. It was noted that Fe(VI) is a very powerful oxidizing agent, and can oxidize most of the cyanide within a few minutes, ca 5 minutes, of contact. The extent of the reduction of Fe(VI) was obtained using the UV-Visible measurements. Further, the UV-Visible data was used to explain the reaction kinetics involved in the redox reaction between ferrate(VI) and cyanide. The pseudo-first-order rate constant was calculated by maintaining the cyanide concentration in excess, with the overall second order rate constant values obtained for initial Fe(VI) concentrations of 1.0 and 0.1 mmol/L. The oxidation of cyanide was again confirmed using a cyanide probe. Fe(VI) was further employed for its possible application in the treatment of industrial wastewaters containing cyanide, along with some heavy metals, such as those obtained from electroplating industries.</P>
Diwakar Tiwari,이승목,C. Lalhriatpuia 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.30 No.-
Hybrid materials (AAS (Al-AMBA-sericite and AHS (Al-HDTMA-sericite)) was obtained and materials arecharacterized by XRD, SEM and IR analytical techniques. Hybrid materials were assessed for efficientremoval of diclofenac from aqueous solutions. Increasing the diclofenac concentration (1.0 to 20.0 mg/L)and pH 2 to 7 favored greatly the removal of diclofenac by AAS and AHS. Background electrolyteconcentrations from 0.0001 to 0.1 mol/L NaCl, insignificantly affected percent removal of diclofenac. Thebreakthrough results were fitted well to the Thomas equation and hence, loading capacity of diclofenacwas found to be 0.561 and 1.056 mg/g for AAS and AHS, respectively.