Catalytic Effects of Manganese (IV), Iron(III), Aluminum, and Silicon Oxides on the Formation of Phenolic Polymers

Abstract

The catalytic effects of three Mn(IV) oxides (birnessite, cryptomelane, and pyrolusite) and short‐range ordered Fe(III), Al, and Si oxides on the darkening of phenolic compound solutions (hydroquinone, resorcinol, and catechol) and the subsequent formation of humic acid (the precipitate formed by acidifying the darkening solution) were investigated. Manganese oxides are very powerful in causing the darkening of phenolic compounds. The rate and degree of the darkening vary with the kinds of Mn oxides, the chemistry of the phenolic compounds, and the pH values of the systems. In the Mn oxide systems, phenolic compounds are converted to humic acid with a relatively high degree of humification (Δlog K: 0.52–0.70; RF: 54–105) through oxidative polymerization. For example, at the initial pH of 6.0, the percent conversion of hydroquinone to humic acid ranged from 36 to 55%. The yields of humic acids formed in the Mn oxide systems are highly correlated with the degree of the darkening measured at 400 nm (r2 = 0.818) and 600 nm (r2 = 0.983). The catalytic effect of Fe oxide on the darkening and the formation of humic acid was relatively limited under the conditions studied. The catalytic effects were not observed in the Al and Si oxide systems. The results obtained in this study indicate that various Mn(IV) oxides common in the environment merit close attention in the abiotic formation of humic substances.

Effect of organic reducing agents on the p sorption product formed on noncrystalline hydrous fe oxide

“…Changes in the IR spectra of P sorbed on Fe gel took place when the amount of hydroquinone was 960/.tmol or higher, which is more than 30 times the lower limit for ascorbic acid. A similar difference in the reactivity among position isomers of polyphenols was also observed in the oxidative reaction of the polyphenols in the presence of hydrous Fe oxide and Mn oxides (Shindo and Huang 1984;McBride 1989).…”

“…Diphenols such as hydroquinone, resorcinol, and catechol were oxidatively darkened by the presence of hydrous Fe oxide though the degree of darkening was much less pronounced than that by Mn oxides (Shindo and Huang 1984). Okazaki et al (1976) suggested that polyphenols are one of the materials responsible for the dissolution of Mn in a paddy soil under reducing conditions.…”

Mangrove tannins in aquatic ecosystems: Their fate and possible influence on dissolved organic carbon and nitrogen cycling

“…As such, the data indicate that the diagenetic progresses were slower in Milli-Q water and that the polymerization of tannins seems to be the dominant process. The difference in the reactivity of tannins in natural waters may thus result from differences in pH, trace-metal concentrations (especially transition metals; Shindo and Huang 1984), and coexisting DOM quality and quantity (Sandvik et al 2000).…”

Effects of surface Fe(III) oxides in a steel slag on the formation of humic-like dark-colored polymers by the polycondensation of humic precursors

“…For example, birnessite, kaolin and nontronite have been reported to enhance the formation of dark-colored polymer from amino acids and quinones [4][5][6][7][8][9]. In addition, oxides of Si, Mn, Al and Fe have also been reported to facilitate the darkening of reaction mixtures that contain humic precursors [10,11].…”