Adsorption and partition of the antibiotic ciprofloxacin in poultry litter

Abstract BACKGROUND The use of antibiotics on a large scale is a common practice in poultry farming. This research investigated the adsorption of the antibiotic ciprofloxacin (CIP) in poultry litter samples to assess the potential risk to ecosystems as a result of the compound mobility. This residue is used directly dispersed in agricultural soils as a biofertilizer. RESULTS Experimental data were evaluated in terms of fits of isotherm models. The mobility of CIP was assessed by the distribution coefficient and the partition coefficient related to organic matter. The studied poultry litter presented a pH of 8.5 ± 0.1, moisture content of 20.3 ± 1.3% and total solids content of 79.8 ± 1.2%, with a high amount of both inorganic matter (57.1 ± 1.7%) and organic matter (42.9 ± 1.7%) content in its composition. The Redlich–Petersen isotherm model satisfactorily described the experimental data, with higher maximum adsorption capacities at more alkaline pHs (pH 8.0 = 3015.0 ± 118.0 μg g −1 , pH 7 = 2916.6 ± 1152.9 μg g −1 and pH 6 = 410.0 ± 18.1 μg g −1 ). The log K d (pH 6 = 0.9, pH 7 = 1.2, and pH 8 = 1.4) and log K oc (pH 6 = 1.3, pH 7 = 1.7 and pH 8 = 1.8) values obtained for the sorption of ciprofloxacin at different pHs in poultry litter were considered low (log K oc < 3.5). CONCLUSIONS The analyte does not tend to adsorb in the poultry litter and might leach to other environmental compartments. The information obtained in this study reinforces the ecotoxicological concern about antibiotic residues in the environment. © 2024 Society of Chemical Industry (SCI).