Kinetics and Mechanisms of Ciprofloxacin Oxidation on Hematite Surfaces
Kinetics and Mechanisms of Ciprofloxacin Oxidation on Hematite Surfaces
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DOI：
10.1021/acs.est.5b02851
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发表时间：
2015-10-20
影响因子：
11.4
通讯作者：
Boily, Jean-Francois
中科院分区：
文献类型：
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作者：
Martin, Sebastien;Shchukarev, Andrey;Boily, Jean-Francois
在过去的20年里，人们对抗生素在矿物表面的吸附进行了广泛的研究，但对其界面性质和转化机理仍有许多需要了解的地方。本研究采用高效液相色谱(LC)、质谱仪(MS)和X射线光电子能谱(XPS)研究了氟喹诺酮类抗生素环丙沙星(CIP)与两种表面较光滑(H10，10~20 nm)和粗糙(H80，80~90 nm)的纳米赤铁矿颗粒之间的相互作用。衰减全反射傅里叶变换红外光谱(ATR-FTIR)提供了在0.01M氯化钠溶液中赤铁矿表面形成CIP的内球双齿络合物的证据，而与pH和粒度无关。ATR-FTIR光谱还显示，吸附的母体CIP分子在至少65h的时间内衰变到其他表面物种。LC/MS检测到水相中有三个子体产物，这支持了这一点。低温XPS揭示的NH3+基团的出现，进一步证明了CIP氧化是通过N-脱烷基哌嗪开环进行的。此外，在程序升温脱附下的真空FTIR实验还表明，吸附副产物的氧化在450℃以上被有效降解，这表明母体和子体产物都有相当强的(分子间)键。这项工作还表明，较粗糙的、可能是多区域的颗粒(H80)产生较慢的CIP分解速度，但通过更复杂的方案发生，而不是在较光滑的颗粒表面(H10)。因此，这项工作揭示了一种重要的抗生素在氧化铁表面结合的关键方面，因此为我们越来越多地了解环境中新出现的污染物的命运提供了额外的限制。
Adsorption of antibiotics at mineral surfaces has been extensively studied over the past 20 years, yet much remains to be learned on their interfacial properties and transformation mechanisms. In this study, interactions of Ciprofloxacin (CIP), a fluoroquinolone antibiotic with two sets of synthetic nanosized hematite particles, with relatively smooth (H10, 10-20 nm in diameter) and roughened (H80, 80-90 nm in diameter) surfaces, were studied by means of liquid chromatography (LC), mass spectrometry (MS), and spectroscopy (vibration and X-ray photoelectron). Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectroscopy provides evidence for inner-sphere bidentate complex formation of CIP at hematite surfaces in 0.01 M NaCl, irrespective of pH and particle size. ATR-FTIR spectroscopy also revealed that the sorbed mother CIP molecule decayed to other surface species over a period of at least 65 h. This was supported by the detection of three daughter products in the aqueous phase by LC/MS. The appearance of NH3+ groups during the course of these experiments, revealed by cryogenic XPS, provides further evidence that CIP oxidation proceeds through an opening of piperazine ring via N-dealkylation. Additional in vacuo FTIR experiments under temperature-programmed desorption also showed that oxidation of sorbed byproducts were effectively degraded beyond 450 degrees C, a result denoting considerably strong (inter)molecular bonds of both mother and daughter products. This work also showed that rougher, possibly multidomainic particles (H80) generated slower rates of CIP decomposition but occurring through more complex schemes than at smoother particle surfaces (H10). This work thus uncovered key aspects of the binding of an important antibiotic at iron oxide surfaces, and therefore provided additional constraints to our growing understanding of the fate of emerging contaminants in the environment.