A kinetic study of the chromium (VI) - arsenic (III) reaction in pyridine-pyridinium buffer solutions containing oxalate

The oxidation of arsenic (III) by chromium (VI) has been studied in pyridine - pyridinium buffers with and without added oxalate ion. The rate law at pH 4.6 for the reactions without oxalate is best described as - d[Cr(VI)]/dt = (0.535 [As(III)]² [Cr(VI)])/(1+187 [As(III)]) This is in accord with the general mechanism for chromium (VI) oxidation proposed by Beattie and Haight. The behavior in pyridine - pyridinium buffers is different from that observed in acetic acid acetate buffers of the same pH. In the presence of oxalate, the observed rate law is - d[Cr(VI)]/dt = (310 [As(III)] [C₂O₄²⁻] [Cr(VI)])/(1+31.0 [As(III)]) In each case the reaction stoichiometry was found to be 3As(III) + 2Cr(VI) = 3As(V) + 2Cr(III). The role of oxalate was found to be catalytic although it was incorporated in the final Cr(III) product. Complex kinetic behavior was observed as a function of pH, [AsIII], and buffer composition.

Name thesis:degree_name

M.S.

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Chemistry

Department dc:contributor.department

Chemistry

Grantor dc:publisher

Virginia Polytechnic Institute and State University

Year dc:date.issued

1985

Author dc:creator

• O'Neal, Stephen Vernon

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language.iso

en

Handle dc:identifier.uri

http://hdl.handle.net/10919/104524

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/104524