Influence of oxytetracycline on boron adsorption at the hematite-water interface: A macroscopic and in situ ATR-FTIR study

The veterinary antibiotic (VA) oxytetracycline (OTC) is used widely in confined animal feeding operations for treating animal diseases, as a prophylactic, and as a growth promoter. Oxytetracycline can enter the environment via various pathways, including runoff from stored manure stockpiles, and applications of manure or contaminated irrigation water to agricultural lands. Once present, OTC may potentially interfere with the biogeochemical cycling of micronutrients, such as boron (B). Iron oxides are known to control the phytoavailability of B via adsorption reactions. Here, we evaluated the influence of OTC on B retention on hematite under various solution properties using macroscopic and in situ attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopic experiments. We found that the extent of B adsorption was reduced in the presence of OTC, whereas OTC retention was not affected by B. The spectroscopic results suggested B retention through the formation of trigonal and tetragonal inner sphere surface species on hematite. These results also indicated that in the presence of OTC the B adsorption mechanisms were altered. Surface complexation modeling, coupled with inner sphere surface complexation of both B and OTC, successfully predicted the B adsorption on hematite and the decrease of B adsorption in the presence of OTC. Our results will improve understanding the biogeochemical cycling of B in the presence of VAs.