Veterinary antibiotics (e.g., lincomycin) are chemicals of emerging concerns because antibiotics from land-applied manures may potently induce antibiotic resistance in bacteria populations, thereby posing serious threats to human health. Biochars are engineered pyrogenic/black carbon produced from pyrolysis of organic feedstocks under oxygen-limited conditions. In this study, we aimed to investigate antibiotics sorption by manure-derived biochars, and their potentials for long-term antibiotics immobilization. We evaluated sorption kinetics of lincomycin in 17 biochars produced from 7 manure feedstocks and one wood feedstock at 300�600 �C. Most biochars quickly reached quasi-equilibrium in the first 2 days, but continued to slowly sorb lincomycin over 6 months. We selected biochars produced at 600 �C for more in-depth studies of this two-phase sorption process, including 2-day quasi-equilibrium sorption isotherms and 6-month long-term sorption kinetics. The 2-day lincomycin sorption was much lower at pH 9.8�10.4 than at pH 5.8�7.4, slightly decreased with increasing solution ionic strength (IS) at pH 5.9�7.6, but remained unchanged with IS at pH 9.8�10.4. Thus, the greater lincomycin sorption at pH below its pKa (7.6) was resulted from electrostatic interaction, which was further corroborated by greater isoelectric point values for lincomyin-loaded biochars, relative to that of lincomycin-free biochars. Nonetheless, because lincomycin sorption capacities at pH 9.8�10.4 were about 54�74% of those at pH 5.9�7.6, non-electrostatic interactions (e.g., van der Waals, hydrogen bonding) appear to be major mechanisms for the entire tested pH range. The slow long-term sorption was likely controlled by intra-particle pore diffusion, which was supported by scanning electron micrographs showing both macro- and micro-pores on biochar surfaces, as well as increased porosity with extended aging in water. Our findings highlight that manure-derived biochars may be used as a long-term sink for veterinary antibiotics via soil amendment.

Sorption of lincomycin in manure-derived biochars: Two-phase kinetics

248th National Meeting (2014)

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