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Title: Thermal behaviour of arsenic oxides (As2O5 and As2O3) and the influence of reducing agents (glucose and activated carbon)
Authors: HELSEN, L.Van den Bulck, E
Van den Bulck, E
VAN BAEL, Marlies 
Issue Date: 2004
Source: THERMOCHIMICA ACTA, 414(2). p. 145-153
Abstract: In this paper the thermal behaviour of pure arsenic oxides ( and As2O3) and the influence of the presence of reducing agents (glucose or activated carbon) on the thermal behaviour of the arsenic oxides are studied through thermogravimetric (TG) analysis. The TG experiments with pure reveal that the reduction reaction As2O5 --> AS(2)O(3) + O-2 does not take place at temperatures lower than 500degreesC. At higher temperatures decomposition is observed. Pure As2O3, however, is already released at temperatures as low as 200degreesC. This release is driven by temperature dependent vapour pressures. Comparing these results with earlier observations concerning the thermal behaviour of chromated copper arsenate (CCA) treated wood, suggests that wood, char and pyrolysis vapours form a reducing environment that influences the thermal behaviour of arsenic oxides. Therefore, the influence of the presence of reducing agents on the thermal behaviour of is studied. First, TG experiments are carried out with mixtures of As2O5 and glucose. The TG and DTG curves of the Mixture are not a simple superposition of the curves of the two pure constituents. The interaction between and glucose results in a faster decomposition of arsenic pentoxide. This effect is more pronounced if the purge gas nitrogen is mixed with oxygen. Second, TG experiments are performed with mixtures of As2O5 and activated carbon. The presence of activated carbon also promotes the volatilisation of arsenic for temperatures higher than 300 degreesC, probably through its reducing action. Extrapolation of the thermal behaviour of these model compounds to the real situation of pyrolysis of CCA treated wood confirms the statement that the reduction of pentavalent arsenic to trivalent arsenic is favoured by the reducing environment, created by the presence of wood, char and pyrolysis vapours. (C) 2004 Elsevier B.V. All rights reserved.
Notes: Katholieke Univ Leuven, Div Appl Mech & Energy Convers, Dept Mech Engn, B-3001 Heverlee, Belgium. Limburgs Univ Ctr, Lab Inorgan & Phys Chem, B-3590 Diepenbeek, Belgium.Helsen, L, Katholieke Univ Leuven, Div Appl Mech & Energy Convers, Dept Mech Engn, Celestijnenlaan 300A, B-3001 Heverlee,
Keywords: arsenic oxides; thermogravimetric analysis; glucose; activated carbon; release
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ISSN: 0040-6031
e-ISSN: 1872-762X
DOI: 10.1016/j.tca.2003.12.016
ISI #: 000221436100007
Category: A1
Type: Journal Contribution
Validations: ecoom 2005
Appears in Collections:Research publications

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