扫描微量热法研究稀腐植酸水溶液

A Study of Dilute Aqueous Solutions of Humic Acids by Scanning Microcalorimetry

用反相柱色谱检测发现,经过不同时间的动物扰动堆肥堆制所获得的腐植酸是由亲水组分和疏水组分组成的,其中疏水组分大体上含有较低的带电基团,这些带电基团很可能是羧酸。在差示扫描量热法测定腐植酸的稀溶液做出的热容-温度图中发现了在约58℃时有一个转折,这表明疏水基团水合作用的增加。我们还发现了在86-90℃的温度区间内有一个热容的突增,这可能是由于＂胶束＂内部的疏水基团的水合作用,因为类似胶束结构的疏水核有＂脱玻作用＂。这表明了随着堆肥时间的增加,腐植酸疏水组分的相对含量和热转变的协同性也增加,它以热容突增的形式表现出来,这很可能是因为＂胶束＂大小的增加。

It has been found by reversed-phase chromatography that humic acids obtained from vermicomposts of different duration of vermicomposting consist of a hydrophilic and a hydrophobic fractions, the hydrophobic fraction having a substantially lower content of charged, probably carboxylic, groups. A change in the sign of the temperature dependence of the heat capacity of dilute aqueous solutions of humic acids at -58 °C has been found by differential scanning microcalorimetry, which indicates an increase in the hydration of hydrophobic groups. A jump-wise increase in heat capacity in the temperature range from 86 to 90 °C was also found, which is perhaps due to hydration of hydrophobic groups in the interior of ＂micelles＂, because of ＂devitrifi cation＂ of the hydrophobic nucleus of micelle-like structures. It was shown that increasing the duration of vermicomposting leads to an increase in the relative content of the hydrophobic fraction of humic acids and in the cooperativity of the thermodynamic transition, which manifests itself as the jump of heat capacity, which probably results from the increase in the ＂micelle＂ size.