Adsorption Mechanism of Di-n-butyl Phthalate Easter on Brown Soil and Red Soil

The study aimed to investigate the adsorption mechanism of di-n-butyl phthalate (DBP) on brown soil and red soil in Shenyang and Hunan province, respectively, China. Adsorption kinetics and isotherms experiments were conducted at 288, 298 and 308 K, respectively. Results of kinetics showed that adsorption of DBP exhibited a two-step process in both brown and red soil. Different models were used to simulate adsorption isotherms and the linear form of Freundlich model fitted to the data best. Sorption capacity was larger and sorption intensity was weaker on the brown soil than the red at same temperature. Sorption capacity decreased and sorption intensity enhanced with temperature increased on both soils. In addition, the thermodynamic data were analyzed which suggested that the process was a spontaneous and exothermal process on the two soils. The values of enthalpy changes were around 40 kJ/mol in the two soils, indicating that the dominant affection was physical adsorption. Furthermore the main forces were hydrogen bond and ion exchange proved by thermodynamic data and infrared spectral analyses.