State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing, 210023, China.
School of Ecology and Environment, Zhengzhou University, Zhengzhou, 450001, China.
Chemosphere. 2022 Jan;286(Pt 1):131641. doi: 10.1016/j.chemosphere.2021.131641. Epub 2021 Jul 24.
The photolysis of amlodipine (AML) as a ubiquitous pollutant in natural water has been extensively studied. Montmorillonite (MMT), a major component of suspended particles in surface aquifers, plays key roles in the natural transportation and transformation of organic contaminants in the environment. However, literature has scarcely focused on whether and how suspended particles affect the phototransformation of AML. This study systematically investigated the phototransformation behavior of AML in MMT suspensions under simulated sunlight. The results obtained showed that MMT significantly enhanced the photolysis of AML. The photodegradation of AML in 0.05 g/L MMT suspension reached 92.2 % after 3 h irradiation under the simulated sunlight. The photodecomposition followed the pseudo-first-order kinetic with a rate constant of 0.803 h in the presence of 0.05 g/L MMT, which is about 19 times larger than that in the absence of MMT (0.0421 h). Further mechanistic investigation suggested that MMT accelerated the photolysis of AML by the formation of surface complexes between cationic amino groups of AML and the negatively charged sites on MMT surface, which greatly facilitated light absorption and electron transfer for the production of cationic radical AML. Meanwhile, the hydroxyl radicals generated by irradiated MMT also played an important role in the photocatalytic degradation of AML. The probable photodegradation pathways of AML in MMT suspension further supported the proposed mechanisms. The toxicity evaluation of phototransformation products of AML with ECOSAR program indicated that photolysis could reduce its potential threats. These findings reveal an important and previously overlooked phototransformation mechanisms of AML in the presence of MMT clays, which is of importance in assessing the environmental fate of other similar organic contaminants.
氨氯地平（AML）作为一种普遍存在于天然水中的污染物，其光解已得到广泛研究。蒙脱土（MMT）是地表含水层悬浮颗粒的主要成分，在环境中有机污染物的自然迁移和转化中起着关键作用。然而，文献几乎没有关注悬浮颗粒是否以及如何影响 AML 的光转化。本研究系统研究了模拟太阳光下 AML 在 MMT 悬浮液中的光转化行为。结果表明，MMT 显著增强了 AML 的光解。在模拟太阳光下辐照 3 小时后，0.05 g/L MMT 悬浮液中 AML 的光降解率达到 92.2%。在 0.05 g/L MMT 存在下，光降解遵循拟一级动力学，速率常数为 0.803 h，而在没有 MMT 的情况下，速率常数为 0.0421 h，约为其 19 倍。进一步的机理研究表明，MMT 通过 AML 的阳离子氨基与 MMT 表面的负电荷位点之间形成表面络合物，加速了 AML 的光解，这极大地促进了光吸收和电子转移，生成阳离子自由基 AML。同时，辐照 MMT 产生的羟基自由基也在 AML 的光催化降解中发挥了重要作用。MMT 悬浮液中 AML 的可能光降解途径进一步支持了所提出的机制。用 ECOSAR 程序对 AML 光转化产物的毒性评价表明，光解可以降低其潜在威胁。这些发现揭示了 AML 在 MMT 粘土存在下的一个重要且以前被忽视的光转化机制，这对于评估其他类似有机污染物的环境归宿具有重要意义。
