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Cr-containing magnetites Fe3−xCrxO4: The role of Cr3+ and Fe2+ on the stability and reactivity towards H2O2 reactions

Paper ID Volume ID Publish Year Pages File Format Full-Text
43431 45969 2007 9 PDF Available
Title
Cr-containing magnetites Fe3−xCrxO4: The role of Cr3+ and Fe2+ on the stability and reactivity towards H2O2 reactions
Abstract

A series of Cr-containing magnetites, Fe3−xCrxO4 (x = 0.00, 0.07, 0.26, 0.42 and 0.51) has been prepared using conventional co-precipitation method. Mössbauer and powder X-ray diffraction measurements suggested the formation of the spinel crystalline phase with initial substitution of Feoct3+ by Cr3+ and for higher Cr contents, chromium also replaces Feoct2+   and   Fetet3+ in the crystalline structure. N2 adsorption/desorption revealed that the presence of Cr has a remarkable effect on the texturial properties of the material decreasing the pore diameter from meso- to micropore with a significant increase on the BET surface area. Thermal analyses (TG and DTA) coupled with XRD and Mössbauer showed that thermal treatment up to 270 °C with O2 leads to the oxidation of Feoct2+ producing Cr-substituted maghemite but at 600 °C the cubic maghemite is converted to the hexagonal hematite and Cr is expelled from the iron oxide structure. The reactivity of Fe3−xCrxO4 was investigated using two H2O2 reactions, i.e. the decomposition to O2 and the oxidation of the dye methylene blue used as model contaminant. The obtained results showed that the presence of Cr directly promoted the H2O2 decomposition. On the other hand, the presence of small concentration of Cr, i.e. Cr0.07 and Cr0.21, caused a significant increase on the activity for the oxidation of the dyes with complete discoloration and high degree of mineralization. The higher activity of Fe2.93Cr0.07O4 was discussed in terms of a coupling of the redox pairs Fe3+/Fe2+ and Cr2+/Cr3+ producing a more efficient regeneration of the Fenton active specie Fe2+.

Graphical abstractThe results showed that the presence of Cr caused a significant increase on the activity for the oxidation of the dyes with complete discoloration and high degree of mineralization. The higher activity of Fe2.93Cr0.07O4 was discussed in terms of a coupling of the redox pairs Fe3+/Fe2+ and Cr2+/Cr3+ producing a more efficient regeneration of the Fenton active specie Fe2+.Figure optionsDownload full-size imageDownload as PowerPoint slide

Keywords
Magnetite; Chromium; Fenton reaction
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Cr-containing magnetites Fe3−xCrxO4: The role of Cr3+ and Fe2+ on the stability and reactivity towards H2O2 reactions
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 332, Issue 1, 1 November 2007, Pages 115–123
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
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Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
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Any Questions? feel free to contact us