OXIDATION OF 1-NAPHTHOL COUPLED TO REDUCTION OF STRUCTURAL FE3+ IN SMECTITE

Abstract

Sorption and transformation of 1-naphthol by a K-smectite (K-SWy-2) were studied using batch sorption isotherms, Fourier-transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). The sorbents included three preparations of the reference smectite clay (SWy-2): (1) whole clay containing naturally occurring carbonate impurities, (2) SWy-2 with the removal of carbonate impurities, and (3) the carbonate-free SWy-2 fraction amended with calcite. For the whole clay and carbonate-free clay amended with calcite, >80% of added 1-naphthol disappeared from aqueous solution within 24 h, corresponding to a sorbed concentration of ≥2 mg/g of clay. In contrast, only 35% of the added 1-naphthol disappeared from solution in the carbonate-free clay after 24 h of exposure. For the clays from the three preparations in this study, 3+ reduction. The spectra also showed evidence of the transformation of 1-naphthol. It suggests that reduction of structural Fe3+ may be coupled to oxidation/polymerization of 1-naphthol. Further transformation of oxidized 1-naphthol, such as by oxidative coupling reactions, is implicated by formation of a dark gray color on the clay and the inability to extract sorbed 1-naphthol.