ADSORPTION BEHAVIOR OF SULEAMETHOXAZOLE ONPURPLE PADDY SOILS COLLECTED FROMTHE WESTSICHUAN PLAIN OF CHINA KINETICSTHERMODYNAMICS AND INFLUENCING FACTORS

摘要

Adsorption of antibiotics on solid particles is a key process controlling their fate in the subsurface. To determine the sorption of the representative sul- fonamides (SAs) on soils, we investigated the effects of initial concentration, temperature, contact time and soil properties on the sorption of sulfamethoxa- zole (SMX) onto two different soil samples (Longxing and Jinjiang purple paddy soils) from the West Sichuan Plain, China. Meanwhile, batch equi- libration experiments were carried out with applica- tion of different kinetics and thermodynamics mod- els. The results showed that both Langmuir and Freundlich isotherm models were well represented the equilibrium adsorption data of SMX, while ki- netic experimental data were well fitted by double- chamber first-order model on both adsorbents. 96% of total adsorption amount were achieved in the ini- tial 1 h for two soils. The adsorption ability enhanced with the increase of initial SMX concentration. Ow-ing to different soil properties, including element composition and endogenous dissolved organic mat- ters (EDOM), the adsorption behavior on two purple paddy soils had a great difference. The single point adsorption coefficient (K) values of Longxing paddysoil were higher than those of Jinjiang paddy soil. And as the temperature rising, the adsorption amount on Longxing paddy soil increased, but there was no obvious regularity in Jinjiang paddy soil. This studywill play an important part in understanding the fate and risk of SMX in soil environment.