Physicochemical Characteristics of Pyroquilon Adsorption and Desorption by Mollisols

The physicochemical parameters associated with pyroquilon adsorption were studied on five Mollisols. The adsorption of pyroquilon was low as revealed from Freundlich adsorption coefficient (K) values which varied from 0.553 to 1.290 and 0.530 to 0.840 at 20 and 40°C, respectively. The exponent 1/n of the Freundlich adsorption isotherm varied from 0.808 to 0.949 and 0.757 to 0.908 at 20 and 40°C, respectively, which indicated considerable linearity in the adsorption isotherms (C-type). Adsorption coefficients were highly correlated with soil organic matter content, as compare to the soil clay content. The organic carbon-water partition coefficient (Koc) values for the soil adsorption were between 46.2 and 56.8 at 20°C and 37.0 and 50.5 at 40°C and were found to be better predicted by models based on aqueous solubility as compared to the octanol water partition coefficient (Kow) of the compound. Desorption of pyroquilon by 0.01 M CaCl2 from soils exhibited hysteresis at both the temperatures. Increased desorption with rise in temperature from 20 to 40°C indicated the endothermic nature of desorption reaction.