Adsorption-Desorption And Thermodynamic Characteristics Of Tylosin On Black Soil Colloids And Minerals

Black soil was sampled from gongzhuling, Jilin province.Soil colloids were obtained through siphon method after dispersion, and separated into coarse clays(0.2-2μm) and fine clays(<0.2μm) by centrifugation. Part of fine and coarse clays were oxidized by H2O2 to remove organic matter. The types of clays were as follows:0.2-2μm organic clay,0.2-2μm inorganic clay,<0.2μm organic clay and<0.2μm inorganic clay. This study investigated the adsorption-desorption, changes in functional groups and thermodynamic characterics of tylosin on soil colloids and minerals.The main results were listed as following:1.The amount of tylosin adsorbed by fine clays was higher than that of coarse clays. Montmorillonite dominates the amount of tylosin adsorption and organic matter also contributes to the tylosin adsorption. Tylosin was adsorbed more tightly on montmorillonite than on Black soil colloids and goethite.2.Ionic species and strength have significant effects on tylosin adsorption on Black soil colloids or minerals.The inhibiting effect of Ca2+ ions was stronger than that of Na+ ions.Meanwhile, the inhibiting effect of cation of soil colloids, kaolinite and goethite was stronger than that of montmorillonite.3.To determine the percentage of various forces involved in tylosin adsorption, tylosin adsorbed by soil colloids and minerals were desorbed by sequential washing with 10 mM Tris-HCl and 100 mM NaCl at pH 7.0.80% of tylosin combined loosely with Black soil colloids which can be desorbed easily; the desorption rate of montmorillonite was the lowest, indicating that it combined with tylosin most closely.4.Fourier transform infrared spectra (FTIR) was employed to investigate the structure characteristics of tylosin, Black soil colloids and minerals as well as their complexes.The results showed that the peaks of macrolide decreased or disappeared after tylosin adsorbed, which may be due to the formation of hydrogen bonds within or between molecules.5.The thermodynamic data of tylosin adsorption on soil colloids and minerals were provided. Tylosin adsorption on Black soil colloids or minerals is a spontaneous process. The adsorption of tylosin on Black soil, kaonite and goethite were exothermic. However, the adsorption of tylosin on montmorillonite was endothermic.6.Tylosin was adsorbed by electrostatic forces on soil colloids; hydrogen bonding and Van der Waals forces played a important role in the adsorption on goethite and the adsorption between tylosin and montmorillonite was a hydrophobic interaction.