Catalytic power of nontronite, kaolinite and quartz and their reaction sites in the formation of hydroquinone-derived polymers

Abstract

The influence of structural and surface properties of nontronite, kaolinite and quartz (0.2−2 μm) on their catalytic power and reaction sites in the formation of hydroquinone-derived humic polymers was investigated. All the reactions observed proceeded abiotically, since microbial growth was not evident in the system studied. The sodium metaphosphate treatment, which was used to block the edges of minerals, decreased the ability of nontronite and kaolinite to catalyze the polymerization of hydroquinone. The sequence of the total humic polymers formed in the reaction systems was: untreated nontronite>treated nontronite>untreated kaolinite>treated kaolinite≅quartz≅control. The data indicate that part of the catalytic power of nontronite and almost all of the catalytic power of kaolinite in the polymerization of hydroquinone are derived from the edges of minerals. On the other hand, the adsorption of humic polymers by the edges of both nontronite and kaolinite only accounts for a small fraction of those adsorbed. The IR and ESR spectra of humic polymers formed in the supernatants of the reaction systems are similar to those of natural humic substances.