Universidade de São Paulo, Avenida Prof. Luciano Gualberto, tr. 3, 380, São Paulo, Brazil.
Instituto Nacional de Tecnologia, Av. Venezuela, 82, Rio de Janeiro, Brazil.
Chemosphere. 2017 Oct;184:981-991. doi: 10.1016/j.chemosphere.2017.06.013. Epub 2017 Jun 18.
Photochemical redox reactions of Fe(III) complexes in surface waters are important sources of radical species, therefore contributing to the sunlight-driven elimination of waterborne recalcitrant contaminants. In this study, the effects of three Fe(III)-carboxylates (i.e., oxalate, citrate, and tartrate) on the UVA photoinduced oxidation of the herbicide amicarbazone (AMZ) were investigated. A Doehlert experimental design was applied to find the Fe(III):ligand ratios and pH that achieved the fastest AMZ degradation rate. The results indicated optimal ratios of 1:10 (Fe(III):oxalate), 1:4 (Fe(III):citrate), and 1:1 (Fe(III):tartrate), with the [Fe(III)] set at 0.1 mmol L and the best pH found to be 3.5 for all the complexes. In addition, a statistical model that predicts the observed degradation rate constant (k) as a function of pH and Fe(III):carboxylate ratio was obtained for each complex, enabling AMZ-photodegradation predictions based on these two variables. To the best of our knowledge, this is the first time that such models are proposed. Not only the pH-dependent speciation of Fe(III) in solution but also the time profiles of photogenerated OH, Fe(II), and HO gave appropriate support to the experimental results. Additional experiments using a sampled sewage treatment plant effluent suggest that the addition of aqua and/or Fe(III)-oxalate complexes to the matrix may also be effective for AMZ removal from natural waters in case their natural occurrence is not high enough to promote pollutant degradation. Therefore, the inclusion of Fe(III)-complexes in investigations dealing with the environmental fate of emerging pollutants in natural waterbodies is strongly recommended.
铁（III）配合物在地表水中的光化学氧化还原反应是自由基物种的重要来源，因此有助于阳光驱动消除水中难降解的污染物。在这项研究中，研究了三种铁（III）羧酸（即草酸盐、柠檬酸盐和酒石酸盐）对除草剂阿米卡星（AMZ）的 UVA 光诱导氧化的影响。采用 Doehlert 实验设计来寻找实现 AMZ 降解率最快的铁（III）：配体比和 pH 值。结果表明，最佳的铁（III）：草酸盐比为 1:10，铁（III）：柠檬酸盐比为 1:4，铁（III）：酒石酸盐比为 1:1，[Fe（III）]设定为 0.1mmol L，最佳 pH 值为 3.5。此外，还获得了一个统计模型，该模型可以预测观察到的降解速率常数（k）作为 pH 值和铁（III）：羧酸比的函数，从而可以根据这两个变量对 AMZ 光降解进行预测。据我们所知，这是首次提出此类模型。不仅溶液中铁（III）的 pH 依赖性形态，而且光生 OH、Fe（II）和 HO 的时间曲线也为实验结果提供了适当的支持。使用取自污水处理厂的出水进行的额外实验表明，向基质中添加 Aqua 和/或 Fe（III）-草酸盐配合物也可能有效去除天然水中的 AMZ，前提是其天然存在不足以促进污染物降解。因此，强烈建议在涉及天然水体中新兴污染物环境归宿的研究中包括铁（III）配合物。
