Biofilm controlled sorption of selected acidic drugs on river sediments characterized by different organic carbon content

The sorption process of selected non-steroidal anti-inflammatory drugs (ibuprofen, naproxen, ketoprofen, diclofenac) on biofilm covered river sediments were investigated in laboratory. In the course of the experiments, the effect of pH of aqueous phase, the effect of TOC (total organic carbon) content of biofilm on the sorption processes were studied. The determination of concentration of drugs was performed by gas chromatography mass spectrometry (GC–MS) both in liquid and solid phases. The pseudo-first-order rate constant of the sorption was found to be 83 min−1. The effect of pH on the sorption of diclofenac was significantly lower than the obtained values in case of the other three drugs. The calculated Kd (sorption coefficient) values increased in the sequence of ibuprofen, naproxen, ketoprofen and diclofenac and varied between 0.1–0.4; 0.2–0.7; 0.2–1.2; 0.2–1.4 kg L−1 respectively, depending on the characteristics of the sediments. The value of Kd × foc showed a straight line as function of foc (fraction of organic carbon) therefore, instead of the widely distributed normalization process (Kd/foc), an empirical equation (Kd = A/foc + B) was suggested for estimation of the Kd values in case of different TOC content sediments.

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► The sorption of four acidic drugs was investigated on biofilm covered sediments.
► The pseudo-first-order rate constant of the sorption was found to be 83 min−1.
► The pH dependence of the sorption of diclofenac was less than the other drugs.
► The sorption coefficient (Kd) depended on the foc also after normalization.
► An empirical equation (Kd = A/foc + B) was suggested for the estimation of Kd.