Characterization of an adsorbed humin-like substance on an allophanic soil formed via catalytic polycondensation between @entity6153 and XXXX , and its adsorption capability to @entity211 .

@entity211 @entity73272 @entity2228 @entity212 @entity7352 @entity5828 @entity505 @entity15 @entity6153
An allophanic soil (AS) catalyzed the formation of dark-colored polymers via polycondensation reactions between @entity6153 and @entity2228 . The organic @entity505 content of the AS was increased from 0.16% to 1.3%, indicating that some of the dark-colored polymers had been adsorbed to the AS. The characteristics of the dark-colored polymers adsorbed on the AS were similar to those of a humin that is not extractable with an aqueous alkaline solution. Such a humin-like substance (HuLS) was separated from the AS by treatment with a mixture of HF and @entity5828 . The HuLS and humic acid-like substance (HaLS), comprising the acid-insoluble fraction in the reaction mixture, were characterized by elemental analysis, size exclusion chromatography, pyrolysis-GC/ @entity15 and @entity7352 NMR. However, the structural features of HaLS and HuLS had many points in common. These results suggest that HuLS-AS can be regarded as an organo-clay complex formed by the strong adsorption of HaLS to the AS. The adsorption of @entity211 ( @entity212 ) to AS and HuLS-AS was examined at pH 5.5. At this pH, the zeta potential of the HuLS-AS showed a negative value. It would, therefore, be expected that @entity73272 anions would adsorb with difficulty to HuLS-AS because of electrostatic repulsion. Nevertheless, the adsorption coefficient for @entity212 to HuLS-AS, as estimated by the Freundlich isotherm, was seven times larger than that for AS. These results show that HuLS, when adsorbed on the AS surface, has the capability to enhance the adsorption of @entity212 .
