Enantioselective Adsorption and Desorption Behaviour of Chiral Ofloxacin and Its Main Metabolites in Agricultural Soils

The occurrence of organic pollutants in the environment and their potential environmental risks are highly influenced by the adsorption and desorption processes onto the soil. In this work, the enantioselective adsorption and desorption behaviour of a chiral antibiotic ofloxacin, and two of its chiral metabolites, N-desmethylofloxacin and ofloxacin N-oxide, was studied in three agricultural soils with different physicochemical properties. The adsorption capacity of the studied compounds was higher than 81.5% in the soils, showing high affinity between studied compounds and soil particles. Considering adsorption kinetic, two steps, which were performed in just a few minutes, were observed: external sorption and intraparticle diffusion. Adsorption isotherms were better fitted to a linear model and were similar between different soils. Only slight differences were observed between enantiomers in their kinetic and adsorption isotherms. Moreover, their desorption was positively correlated with soil electrical conductivity but negatively correlated with soil cation exchangeable capacity.