Abstract--The catalytic power of Ca-nontronite, Ca-bentonite, and Ca-kaolinite in promoting the abiotic ring cleavage of pyrogallol (1,2,3-trihydroxybenzene) and the associated formation of humic polymers was studied in systems free of microbial activity. The presence of Ca-kaolinite and especially Ca-nontronite in the pyrogallol solutions at pH 6.00 greatly enhanced the absorbance at both 472 and 664 nm of the supernatants. At an initial pH of 6.00 and at the end of a 90-hr reaction period, the amounts of CO: released from the ring cleavage of pyrogallol and the yields of the resultant humic polymers formed in the reaction systems followed the same sequence: Ca-nontronite > Ca-kaolinite > Ca-bentonite. The data indicate that the catalytic power of Fe(III) on the edges and in the structure of nontronite was substantially greater than that of A1 on the edges of kaolinite and montmorillonite and of a small amount of Fe(III) in the structure of montmorillonite in promoting the reactions. The infrared and electron spin resonance spectra and the solid-state, cross-polarization magic-angle-spinning 13C nuclear magnetic resonance spectra of humic polymers formed in the reaction systems resembled those of natural humic substances.

The objective of this study was to investigate the catalytic power of nontronite (0.2‐2 µm) in the polycondensation of pyrogallol (1,2,3‐trihydroxybenzene) and glycine and the associated reactions involving the ring cleavage of pyrogallol and the decarboxylation and deamination of glycine in systems free of microbial activities. At the end of a 90‐h reaction period, nontronite catalyzed the ring cleavage of pyrogallol, as shown by the release of CO2. The release of CO2 in the nontronite‐pyrogallol system was six times higher than that for pyrogallol alone. Nontronite also catalyzed decarboxylation and deamination of glycine, as shown by the release of CO2 and NH3. The ability of nontronite to catalyze deamination of glycine was substantially enhanced by the presence of pyrogallol. Polycondensation of glycine and pyrogallol was greatly catalyzed by nontronite. This is indicated by the absorbances of the molecular visible absorption spectroscopy of the supernatants, yields of total N‐containing humic acids (HA) and fulvic acids (FA) and the fraction of glycine converted to nitrogenous polymer. The infrared (IR) and electron spin resonance (ESR) spectra of HA and FA formed in the supernatants of the reaction systems were similar to those of soil HA and FA. The sequence for the amounts of the total humic polymers formed in the system was: nontronite‐glycine‐pyrogallol > nontronite‐pyrogallol > glycine‐pyrogallol > pyrogallol. The catalytic effects of nontronite on the C turnover, N transformations, and humic substance formation in soils thus merit attention.

Abstract--The catalytic power of Ca-nontronite (0.2-2 urn) for the polycondensation of phenols and glycine and the associated reactions that involve the ring cleavage of phenols and the deearboxylation and deamination of glycine was studied in systems free of microbial activity. At the end ofa 90-hr reaction period, the amount of CO2 released from the Ca-nontronite-glycine-pyrogalloI, Ca-nontronite-glycinecatechol, and Ca-nontronite-glyeine-hydroquinone systems were 5.1, 8.7, and 11.6 times higher, respectively, than those from the respective nontronite-free systems, showing the catalytic role of Ca-nontronite in the ring cleavage of phenols and the decarboxylation of glycine. The release of CO2 and NH3 from the Ca-nontronite-glycine system revealed that Ca-nontronite can catalyze decarboxylation and deamination of glycine. The ability of Ca-nontronite to catalyze the deamination of glycine was substantially enhanced by the presence of a phenol. The visible absorbances at both 472 and 664 nm of the supernatants, the total yields of N-containing humic polymers, and the fractions of glycine converted to nitrogenous polymers indicated that polycondensation of glycine and phenol was greatly catalyzed by Ca-nontronite. The total N-containing humic polymers formed in the systems decreased in the order: Ca-nontroniteglycine-pyrogallol > Ca-nontronite-glycine-cateehol > Ca-nontronite-glycine-hydroquinone > glycinepyrogallol > glycine-hydroquinone > glycine-catechol. The infrared and electron spin resonance spectra of humie acid (HA) and fulvic acid (FA) formed in the supernatants of the reaction systems were quite similar to those of soil HA and FA. The catalytic power of Ca-nontronite in affecting the ring cleavage of phenols, deamination and decarboxylation of amino acids, and formation ofhumic substances derived from phenols with amino acids in soils and the related environments thus merits attention.

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