Sorption of cefdinir, memantine, praziquantel and trimethoprim in sediment and soil samples

The everyday use of various pharmaceuticals to treat humans or animals means that they are increasingly found in the environment. Contamination of the soil can cause the active ingredients to be strongly sorbed to the soil or sediment. In the worst case, they can also be expected to occur in the aquatic environment due to their different polarity. In this study, four drugs from different therapeutic classes (trimetoprim, memantine, cefdinir, praziquantel) were used in dissolved form in two sediment and three soil samples to obtain data that can describe their fate and behavior in the environment. The sorption affinities of the pharmaceuticals were described using linear, Freundlich and Dubinin-Radushkevich sorption isotherms. The highest K_d values were obtained for cefdinir, while memantine and praziquantel tended to be present in water due to their very low sorption coefficients. The studied influence of pH showed a negative trend for memantine and trimetoprim, while an increase in ionic strength resulted in higher K_d values for all drugs. The sorption mechanism for all tested samples was best described by the pseudo-secondary kinetic model (R² > 0.9999).