Coprecipitation of ferrihydrite, enoxacin, and citrate for their transformation

The distribution and degradation of antibiotic enoxacin in ferrihydrite-enoxacin and ferrihydrite-enoxacin-citrate coprecipitates phase transformation processes were investigated through combined experiments and theoretical calculations. Results indicated that the coprecipitates, including enoxacin and citrate, suppressed the transformation of coprecipitates into hematite. The proportions of hematite in ferrihydrite-enoxacin and ferrihydrite-enoxacin-citrate were 11.7% and 8.4% lower than that in pure ferrihydrite, respectively. Most enoxacin was degraded mainly through •OH generated from Fe(II)/Fe(III) intervalence changing and citrate promoted the degradation of enoxacin during the phase transformation process. The transformation products were less toxic than the enoxacin. Our results strongly suggest that the coprecipitation transformation of fluoroquinolones antibiotics and ferrihydrite may play a larger role in their environmental fate and effects.