TiO2 photocatalytic degradation of the flame retardant tris (2-chloroethyl) phosphate (TCEP) in aqueous solution: A detailed kinetic and mechanistic study
TiO2 photocatalytic degradation of the flame retardant tris (2-chloroethyl) phosphate (TCEP) in aqueous solution: A detailed kinetic and mechanistic study
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DOI：
10.1016/j.jphotochem.2019.03.026
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发表时间：
2019-05-15
影响因子：
4.3
通讯作者：
O'Shea, Kevin E.
中科院分区：
文献类型：
--
作者：
Abdullah, A. M.;O'Shea, Kevin E.
天然水系统中存在卤代有机磷酸盐阻燃剂受到广泛关注，因为它们对人类健康和环境构成潜在威胁。TiO 2在350 nm处的光催化降解导致磷酸三（2-氯乙基）酯（TCEP）的快速降解。在特定浓度下观察到的降解遵循伪一级动力学。在18-270 μ M的范围内，取决于初始浓度，表观速率常数从0.28到0.03 min（-1）变化，表明非均相降解过程可能是由TiO 2表面的传质（吸附/脱附）控制的。降解动力学也符合Langmuir-Hinshelwood模型，表观平衡常数（K-LH）和反应性常数（k（rxn-LH））的表观动力学参数分别为0.03 μ M-1和13.1 μ M min（-1）。H-1-和P-31-NMR研究表明，烷基酯链（磷酸烷基酯）的顺序氧化，最初导致二酯产物，随后形成单酯并最终产生磷酸酯。在强碱性条件下，降解增强，从pH 4到9，降解相对恒定，而在高酸性条件下，降解受到抑制。实现了有效的矿化，表现为优异的氯化物（98%）和磷酸盐（94%）质量平衡以及总有机碳（TOC）损失> 95%。添加等摩尔量的羟基自由基清除剂香豆素导致降解显著减少，表明羟基自由基介导降解过程。这些结果表明，TiO 2光催化氧化处理有机磷阻燃剂污染的水溶液有希望。
The presence of halogenated organophosphate flame retardants in natural water systems is a widespread concern because of their potential threat to human health and the environment. TiO2 photocatalysis at 350 nm leads to rapid degradation of tris (2-chloroethyl) phosphate (TCEP). The observed degradation follows pseudo-first-order kinetics at a specific concentration. The apparent rate constants varied from 0.28 to 0.03 min(-1) depending on the initial concentrations over the range of 18-270 mu M, indicating the heterogeneous degradation process is likely controlled by mass transfer (adsorption desorption) at the surface of TiO2. The degradation kinetics also fit the Langmuir-Hinshelwood model with apparent kinetic parameters of 0.03 mu M-1 and 13.1 mu M min(-1) for the apparent equilibrium constant (K-LH) and the reactivity constant (k(rxn-LH)) respectively. H-1- and P-31-NMR studies indicate sequential oxidation of the alkyl ester chains (alkyl phosphate), initially leading to the diester product, followed by the formation of the monoester and ultimately producing phosphate. Under strongly alkaline conditions the degradation is enhanced, from pH 4 to 9 the degradation is relatively constant, while under highly acidic conditions the degradation is inhibited. Effective mineralization is achieved as demonstrated by excellent chloride (98%) and phosphate (94%) mass balances as well as the loss of total organic carbon (TOC) > 95%. The addition of an equal molar amount of the hydroxyl radical scavenger, coumarin, leads to pronounced reduction in degradation indicating hydroxyl radicals mediate the degradation process. These results demonstrate TiO2 photocatalytic oxidation has promise for the treatment of aqueous solutions contaminated with organophosphate flame retardants.