Adsorption Behavior and Influencing Factors of Sulfamethoxazole and Carbamazepine on Porous Media

Sulfamethoxazole (SMX) and carbamazepine (CBZ) are pharmaceutically active compounds that are frequently detected in aquatic environments. Once they enter the water-soil system, these compounds pose potential risks to the ecological environment and human health. To investigate the adsorption behavior of SMX and CBZ by different soils, the adsorption kinetics, isothermal adsorption characteristics of SMX and CBZ in two typical porous media (silt and fine sand), and the influences of solution pH value, dissolved humic acid (DHA), and soil mineral components were examined. The results show that the adsorption of SMX and CBZ on porous media conformed to both the Lagergren pseudo-second-order kinetic model and the Langmuir isothermal adsorption model, which were characterized by an initial rapid adsorption followed by slow equilibrium. The adsorption process belongs to the monolayer adsorption and is controlled by chemical reaction. The adsorption of SMX by porous media is a spontaneous and exothermic process, while the adsorption of CBZ is an endothermic reaction. Under experimental conditions, the maximum adsorption capacities of silty soil with small particle size, high organic matter content and large specific surface area for SMX and CBZ were 3.0 times and 2.3 times larger than those of fine sand, respectively. The adsorption of SMX was mainly influenced by the electrostatic attraction on mineral surfaces and the partitioning effect of organic matter, while the adsorption of CBZ was dominated by the partitioning effect. With the increase of solution pH value (from 5.0 to 9.0), the adsorption capacity of anionic SMX decreased significantly due to the influence of electrostatic repulsion, while the adsorption capacity of molecular CBZ changed insignificantly. The coexistence of dissolved humic acid (8–50mg/L) in the solution had a competitive inhibitory effect on the adsorption of SMX and CBZ by porous media, while montmorillonite and iron oxides in the porous media had a promoting effect on the adsorption of SMX and CBZ. The BRIEF REPORT is available for this paper at http://www.ykcs.ac.cn/en/article/doi/10.15898/j.ykcs.202407110154.