ADSORPTION BEHAVIOR OF SULFAMETHOXAZOLE ON PURPLE PADDY SOILS COLLECTED FROM THE WEST SICHUAN PLAIN OF CHINA KINETICS THERMODYNAMICS AND INFLUENCING FACTORS

Adsorption of antibiotics on solid particles is a key process controlling their fate in the subsurface. To determine the sorption of the representative sulfonamides (SAs) on soils, we investigated the effects of initial concentration, temperature, contact time and soil properties on the sorption of sulfamethoxazole (SMX) onto two different soil samples (Longxing and Jinjiang purple paddy soils) from the West Sichuan Plain, China. Meanwhile, batch equilibration experiments were carried out with application of different kinetics and thermodynamics models. The results showed that both Langmuir and Freundlich isotherm models were well represented the equilibrium adsorption data of SMX, while kinetic experimental data were well fitted by double chamber first-order model on both adsorbents. 96% of total adsorption amount were achieved in the initial 1 h for two soils. The adsorption ability enhanced with the increase of initial SMX concentration. Owing to different soil properties, including element composition and endogenous dissolved organic matters (EDOM), the adsorption behavior on two purple paddy soils had a great difference. The single point adsorption coefficient (K) values of Longxing paddy soil 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 study will play an important part in understanding the fate and risk of SMX in soil environment.