Environmental catalysis and materials

Characterization and reactivity of biogenic manganese oxides for ciprofloxacin oxidation


Jinjun Tu , Zhendong Yang , Chun Hu , Jiuhui Qu

DOI:10.1016/S1001-0742(13)60505-7

Received June 24, 2013,Revised September 03, 2013, Accepted , Available online April 01, 2014

Volume 26,2014,Pages 1154-1161

Biogenic manganese oxides (BioMnOx) were synthesized by the oxidation of Mn(Ⅱ) with Mn-oxidizing bacteria Pseudomonas sp. G7 under different initial pH values and Mn(Ⅱ) dosages, and were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and UV-Vis absorption spectroscopy. The crystal structure and Mn oxidation states of BioMnOx depended on the initial pH and Mn(Ⅱ) dosages of the medium. The superoxide radical (O2·-) was observed in Mn-containing (Ⅲ/Ⅳ) BioMnOx suspensions by electron spin resonance measurements. BioMnOx(0.4)-7, with mixed valence of Mn(Ⅱ/Ⅲ/Ⅳ) and the strongest O2·- signals, was prepared in the initial pH 7 and Mn(Ⅱ) dosage of 0.4 mmol/L condition, and exhibited the highest activity for ciprofloxacin degradation and no Mn(Ⅱ) release. During the degradation of ciprofloxacin, the oxidation of the Mn(Ⅱ) formed came from biotic and abiotic reactions in BioMnOx suspensions on the basis of the Mn(Ⅱ) release and O2·- formation from different BioMnOx. The degradation process of ciprofloxacin was shown to involve the cleavage of the hexatomic ring having a secondary amine and carbon-carbon double bond connected to a carboxyl group, producing several compounds containing amine groups as well as small organic acids.

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