Simultaneous Studies of Redox Reaction of Chromium(VI) and Arsenic(III) in Aqueous Phase: A Kinetic and Mechanistic Approach
Iorhuna, T. Boniface *
Department of Chemistry, Taraba State University, P.M.B. 1167, Jalingo, Taraba, Nigeria.
Wuana, A. Raymond
Department of Chemistry, Federal University of Agriculture Makurdi, Makurdi, Benue State, Nigeria.
Yiase, G. Stephen
Department of Chemistry, Benue State University, Makurdi, Benue, Nigeria.
*Author to whom correspondence should be addressed.
Abstract
A kinetic and mechanistic approach was used to simultaneously study the oxidation of As(III) and reduction of Cr(VI) in aqueous phase, and in the presence of Fe(III). Reactions were monitored by UV-visible spectrophotometry. The stoichiometry of the reaction was 
. The rate equation for the reaction is proposed as 
where k2 is the second order rate constant. The reaction was not affected by Fe(III) ions within the studied concentration range of 0.001 – 0.009 molL-1. From the reaction between 
a plausible mechanism involving an ester formation by the reactants leading to the eventual formation of As(V) and Cr(III) was proposed.
Keywords: Oxidation-reduction, arsenic(III), chromium(VI), kinetics, mechanism