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Gamma-radiation effects on the reduction of hematite to iron in the graphite-iron(III) oxide system

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Abstract

The effects of60Co-gamma radiation and of various sample composition on the reduction of hematite to iron in the graphite-iron(III) oxide system in air were studied using isothermal and dynamic TG techniques. Kinetic analysis of isothermal data were performed according to various theoretical models of heterogeneous reactions and the results showed that the three-dimensional phase boundary model gives the best fit of data. Analysis of dynamic TG data were made using Ozawa integral method, Coats-Redfern method and a composite method based on the modified Coats and redfern equation. The activation parameters were calculated and the results of the different methods were compared and discussed.

Radiation apparently did not introduce a change in the reaction model or mechanism. However, there is a decrease in activation energy and frequency factor upon irradiation and a decrease in the half-life time of the reaction which is remarkable at the higher temperatures and higher doses.

Zusammenfassung

Mittels isothermer und dynamischer TG wurde im Graphit-Eisen(III)oxidsystem in Luft der Einfluß von60Co-Gammastrahlung und von verschiedenen Probenzusammensetzungen auf die Reduktion von Hämatit zu Eisen untersucht. Entsprechend verschiedener theoretischer Modelle heterogener Reaktionen wurde eine kinetische Analyse der isothermen Daten durchgeführt und die Ergebnisse zeigten, daß das dreidimensionale Phasengrenzenmodell die beste Übereinstimmung liefert. Die Analyse der dynamischen TG-Daten wurde mittels der Integralmethode von Ozawa, der Coats-Redfem-Methode und einer zusammengesetzten Methode auf der Grundlage der modifizierten Coats und Redfern Gleichung durchgeführt. Die Aktivierungsparameter wurden berechnet und die Ergebnisse der verschiedenen Methoden miteinander verglichen und diskutiert.

Strahlung scheint keine Änderung des Reaktionsmodelles oder des Mechanismus hervorzurufen. Durch Bestrahlung gibt es aber ein Absinken der Aktivierungsenergie und des Frequenzfaktors sowie ein Absinken der Halbwertszeit der Reaktion, was bei höheren Temperaturen und höherer Dosis bemerkenswert groß ist.

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Author notes

  1. A. A. El Bellihi & H. M. El Diefallah

    Present address: Department of Chemistry, Faculty of Science, Benha University, Benha, Egypt

Authors and Affiliations

  1. Department of Chemistry, Faculty of Science, King Abdulaziz University, P.O.Box 9028, 21413, Jeddah, Egypt

    S. N. Basahel, A. A. El Bellihi & H. M. El Diefallah

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  1. S. N. Basahel
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  2. A. A. El Bellihi
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  3. H. M. El Diefallah
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Basahel, S.N., El Bellihi, A.A. & El Diefallah, H.M. Gamma-radiation effects on the reduction of hematite to iron in the graphite-iron(III) oxide system. Journal of Thermal Analysis 39, 87–95 (1993). https://doi.org/10.1007/BF02235449

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  • DOI: https://doi.org/10.1007/BF02235449

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