Kinetics of the Chromium(VI)/Thiourea Reaction in the Presence of Polyacrylamide

Abstract

ABSTRACT The formation of chromium(III)-polyacrylamide gels was followed kinetically using spectrophotometric methods. The rate of chromium(VI) species conversion by thiourea and bisulfite was monitored to find a kinetic model for the oxidation/reduction reaction. The third order model found here shows first-order dependence on chromium(VI) concentration on thiourea and on pH. Additional results of the thiourea study show that a constant amount of chromium(VI) is consumed at gelation regardless of the initial concentration of that species, indicating that the Cr(VI) reduction reaction may be the rate-determining step in gelation. No such model or constant conversion for the bisulfite-reduced reaction could be determined.