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四溴双酚A(TBBPA)是最常用的溴代阻燃剂,已广泛分布于各种环境基质中,并引起了人们对其内分泌干扰,细胞致死性和难降解性的广泛关注[1-4]。为了去除TBBPA,微生物[5]、δ-MnO2[6]、臭氧[7]、漆酶[8]、硫酸根自由基[9-10]等氧化方法以及低价金属还原技术被开发出来[11-12]。然而,这些方法存在能源成本高且会有毒性更强的产物生成(如:双酚A和溴酸盐)的弊端[6-7]。本课题组最近的研究发现,在碱性条件下(如pH 10),FeⅢ-TAML/H2O2体系可以在1 min内实现TBBPA的完全去除以及部分脱溴和矿化[13-14]。
FeⅢ-TAML活化剂由于其高效和低毒性而被归属于新型绿色催化剂。反应中,FeⅢ-TAML需要先被氧化剂,如:H2O2和过硫酸盐等[15],活化形成高价铁-氧配合物,即FeIV-TAML[16]或FeⅤ-TAML[17])。FeⅣ-TAML或FeV-TAML作为芳香类有机污染物的主要氧化活性物种具有很强的氧化能力和选择性[14, 18-19]。因此,FeⅢ-TAML已被用于降解多种芳香族有机污染物,包括染料[20]、雌激素性化学品[21-22]、软体动物杀虫剂[23]、磷酸盐农药[24]以及持久性卤代酚类物质[15, 18-19]。FeⅢ-TAML的局限性之一是FeⅢ-TAML(分子结构如图1)的反应活性具有很强的pH依赖性,在碱性条件下活性高,而在中性或酸性条件下会急剧降低[25-26]。
FeⅢ-TAML分子结构:
研究发现,FeⅢ-TAML除了反应活性具有很强的pH依赖性之外,污染物的降解路径也会发生改变。用FeⅢ-TAML/H2O2体系催化氧化双酚A,发现双酚A在碱性条件下可以很快被降解,而在中性条件下去除速率显著降低且会生成胶状物质[27]。TBBPA是双酚A的结构类似物,很有可能发生相似的现象。此外,以前的研究仅仅针对FeⅢ-TAML/H2O2体系对TBBPA不同pH条件下的降解效率,尚未对TBBPA在不同pH条件下的转化路径进行研究。
在这项工作中,本课题组探究了pH 7.5和10条件下FeⅢ-TAML/H2O2体系对TBBPA的降解动力学,分析了不同pH条件下TBBPA的降解产物,并结合理论计算推导了FeⅢ-TAML/H2O2体系在不同pH条件下降解TBBPA的反应路径。此外,本研究测定了TBBPA及其不同pH条件下的降解产物对发光菌的发光抑制率,采用定量结构活性相关性模型预测了降解产物对不同营养级生物的急性和慢性毒性.
FeⅢ-TAML/H2O2体系催化氧化四溴双酚A的pH依赖性
pH-dependent catalytic oxidation of tetrabromobisphenol A by the FeⅢ-TAML/H2O2 system
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摘要: 四酰胺基六甲基苯基环铁配合物(FeⅢ-TAML)因其对芳香类有机污染物的高活性和选择性而备受关注。在这些芳香类有机污染物中,FeⅢ-TAML对酚类化合物表现出很高的降解效率。然而,以前的研究表明,FeⅢ-TAML/H2O2体系对酚类物质的降解除了反应活性具有很强的pH依赖性之外,酚类物质的降解路径和产物也会随pH变化而产生差异。本研究通过FeⅢ-TAML/H2O2体系在近中性和碱性条件下对四溴双酚A(TBBPA)的降解,发现TBBPA的降解速率具有显著的pH依赖性,并随着pH升高而升高。与碱性条件不同,在中性条件下可以检测到耦合产物,表明FeⅢ-TAML/H2O2体系对TBBPA的降解路径也表现出显著的pH依赖性。此外,本研究对TBBPA及其不同pH条件下的降解产物也进行了毒性评估,发现近中性条件下生成的耦合产物具有更高的急性毒性和慢性毒性。这项工作揭示了高价铁配合物催化氧化有机污染物的反应机理,评估了有机污染物及其降解产物的毒性,为FeⅢ-TAML的实际应用提供理论指导。
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关键词:
- 四溴双酚A /
- 四酰胺基六甲基苯基环铁 /
- 催化氧化 /
- pH依赖性 /
- 毒性评估
Abstract: Iron(Ⅲ)-tetraamidomacrocyclic ligand (FeⅢ-TAML) has attracted great attention due to its high activity and selectivity for the degradation of aromatic organic pollutants. Among these aromatic contaminants, FeⅢ-TAML shows high efficiency for the removal of phenolic compounds. However, as reported in previous literatures, the degradation of phenols by the FeⅢ-TAML/H2O2 system is strongly pH-dependent, and the degradation pathways and products of phenols will also vary with pH changes. In this study, the FeⅢ-TAML/H2O2 system is used to decompose tetrabromobisphenol A (TBBPA) under near neutral and alkaline conditions. It is found that the degradation rate of TBBPA was pH-dependent and increased with increasing pH levels. Unlike the reaction under alkaline conditions, coupling products can be detected for TBBPA after degradation by the FeⅢ-TAML/H2O2 system under near neutral pH conditions. This suggests that the degradation path of TBBPA also exhibits a significant pH-dependence. In addition, this study also evaluates the toxicities of TBBPA and its degradation products generated under different pH conditions, finding that the coupling products generated under near-neutral conditions exhibit higher acute and chronic toxicity. This study reveals the reaction mechanism of the catalytic oxidation of organic pollutants by high-valent iron complexes, evaluates the toxicity of organic pollutants and their degradation products, and provides theoretical guidance for the practical application of FeⅢ-TAML. -
表 1 TBBPA及其降解产物的ECOSAR毒性预测.
Table 1. Toxicity of TBBPA and its degradation intermediates predicted by the ECOSAR program.
化合物 Compound 急性毒性/(mg L−1)Acute toxicity 慢性毒性/(mg L−1)Chronic toxicity 毒性分级Hazard category 水蚤(LC50)Daphnid 鱼(LC50)Fish 水蚤Daphnid 鱼Fish TBBPA 0.023 0.023 0.006 0.006 极高毒 P1 3.188 6.078 0.605 0.736 高毒 P2 0.426 0.418 0.081 0.063 极高毒 P3 0.167 0.555 0.038×10−3 0.088×10−3 极高毒 P4 0.022 0.022 0.006 0.006 极高毒 P4’ 0.115 0.058 0.022 0.011 极高毒 P5 48.618 359.240 7.842 39.438 中毒 P6 179.049 1961.876 29.659 205.323 低毒 -
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