The efficieny of toxic chromate reduction by a conducting polymer (polypyrrole): Influence of electropolymerization conditions

Studies of pollution due to hexavalent chromium are important because it re presents a risk to human health and the environment. Hexavalent chromium is a toxic substance and has been found to be carcinogenic. Fortunately, its reduced form, Cr(III), is much less toxic. This paper discusses the remedia tion Cr(VI) by its reduction in aqueous media by polypyrrole (PPy)-coated r eticulated vitreous carbon substrates (RVC). The study is focused on the ef fect of PPy-film electropolymerization conditions and its efficiency toward the reduction of toxic chromate. We have studied parameters such as the in fluence of the polymerization electrolyte, the scan rate, the potential lim its, and the polymerization cycles concerning the reduction capability of t he film. Key results obtained in the present study show that in the presenc e of different anions during formation of the PPy film, the efficiency of c hromate reduction depends on the nature of the anion. We found that the fil ms prepared and treated in the presence of Kl performed much better and las ted much longer than those prepared in the presence of KF. Films synthesize d at lower scan rates, and higher positive potential limits showed higher c hromate reduction efficiencies. Some of our results show reduction of ca. 1 00% of Cr(VI) from a 10 mg/L solution, even after using the film in 20 cont acts with the chromium solution, with films synthesized in KBr and KI elect rolytes, at a scan rate of 20 mV/s, between -0.3 and 0.9 V and 40 polymeriz ation cycles. Our study shows that remediation of Cr(VI) by reduction with PPy-coated substrates could be developed into an effective method toward th e solution of this problem.