Yulia Gennadyevna Izosimova

The content of benzoic acid in the water extract from the organic horizons of the podzolic soil was found to be 3,27 and 1,83 ppm in the horizons L and F, respectively, and it decreases to hundredths of ppm in the mineral horizons. It was established in an experiment, that with an increase in the benzoic acid equilibrium concentration of from 0,02 to 1,45 mmol/L, its sorption onto Ca-montmorillonite increases from 5,61 to 15,34 mmol/kg. Taking into account the content and mineralogical composition of the clay fraction, the expandable clays in the upper mineral horizons of the podzolic soil are capable to retain from 0,06 to 0,15 mmol of benzoic acid per 1 kg of soil within the same range of equilibrium concentrations. The linear equation and the Freundlich model provide the best fit to the measured data. It is assumed that, under experimental conditions, the main mechanisms of benzoic acid sorption were the cation bridging or water bridging and the electrostatic interaction of benzoate with positively charged silanol and aluminol groups on edges of montmorillonite particles. The absorption of benzoic acid in the interlayer space of the mineral wasn’t observed.