Reduction of hexavalent chromium in aqueous solutions by polypyrrole .2. Thermodynamic, kinetic, and mechanistic aspects

This article elaborates on an earlier communication from this laboratory that described a new approach to the electrochemical remediation of Cr(VI) based on the use of a conducting polymer, namely, polypyrrole. The polymer film is shown to act as a catalyst for Cr(VI) reduction by shuttling reversibly between its two redox states. The thermodynamic and kinetic aspects of the process are described. The influence of solution pH, substrate [Cr(VI)] initial concentration, and the number of pyrrole units in the polymer film, on the extent of reduction of Cr(VI) is presented. Cyclic voltammetry experiments designed to probe the catalytic nature of the reduction process are described as are stability tests for the polypyrrole film electroactivity on extended contact with Cr(VI) containing solutions.