Decolorization of Azo Dyes by PIP Tin Balls in Citric Acid Solution

抄録

PIP tin balls effectively decolorized azo dyes in citric acid solution and produced p-aminobenzene sulfonic acid (ABS) and 1-amino-2-naphthol (1A2N) stoichiometrically by reductive cleavage of Orange II. We performed the decolorization of Orange II under stirring condition to investigate the effect of dissolved oxygen. The decolorization rates estimated using pseudo first-order reactions under anaerobic conditions were significantly higher than those under aerobic conditions. The reductive cleavage of Orange II was inactivated after repeated decolorization reactions in the presence of oxygen. This was associated with the formation of a white precipitate on the surface of the inactivated PIP tin balls, which formed a protective film of oxidized Sn compounds. The surface-area-normalized first-order reaction rate constant (k_SA) for 0.3 mM Orange II, was 0.22 (l m^-2 min^-1), which was similar to the previously reported value for Orange II decolorization using zero-valent iron powder. Oxidation of metallic tin in the structure of PIP tin balls was considered to be an important factor for the reaction mechanism in the presence of citric acid.