Research Laboratory on Energy and Matter for Nuclear Science Development (LR16CNSTN02), National Center for Nuclear Science and Technologies, Tunis, Tunisia.
Univ. Manouba, ISBST, LR11-ES31 BVBGR, Biotechpole Sidi Thabet, Ariana, Tunisia.
Environ Technol. 2022 Nov;43(26):4147-4155. doi: 10.1080/09593330.2021.1944325. Epub 2021 Jun 28.
An efficient gamma radiolytic decomposition of one of the extensively used herbicides in the world quizalofo-p-ethyl (QPE) was explored under different experimental conditions. Aqueous solutions of QPE were irradiated by gamma rays emitted by a Cobalt 60 source. QPE aqueous solutions were irradiated at doses of 0.5-3 kGy with 26.31 Gy min dose rate. Obtained results indicated that removal efficiency of 98.5% and 73% of QPE were obtained, respectively, in absence and in presence of dissolved oxygen. Change of absorption spectra, pH effect and Total Organic Carbon (TOC) were carried out and studied. It was found that all absorption bands decreased with increasing irradiation dose and disappear totally after 3 kGy applied dose. Three pH conditions (pH = 10, pH = 6.2 and pH = 3) were applied in radiolytic degradation of QPE showing that the best removal efficiency has been found for neutral pH. Interestingly, the % TOC removal reaches 98% at 3 kGy indicated practically total mineralization. Furthermore, spectrophotometric analyses argued in favour of a pseudo-first-order kinetic of QPE degradation. The resulting apparent rate constant value is approximately = (0.012 ± 0.001) min. Finally, several by-products such as 6-chloroquinoxalin -2-ol, 2-(4-hydroxy-phenyoxy) propionate, 1,4-hydroquinone, quinone, 4-chlorobenzene-1,2diol and 1,2,4-benzenetriol were identified by gas chromatography-mass spectrometry (GC/MS) evidencing that radiation process starting with the fragmentation of the molecule involving the hydroxyl radical, which is generated by the radiolysis of water. Based on the identification intermediates, a degradation mechanistic schema of QPE has been proposed.
在不同的实验条件下，探索了一种广泛用于世界的除草剂——喹禾灵- p -乙酯（QPE）的高效伽马辐射分解方法。用钴 60 源发射的伽马射线辐照 QPE 的水溶液。QPE 水溶液在 0.5-3 kGy 的剂量下，以 26.31 Gy min 的剂量率辐照。得到的结果表明，在没有和存在溶解氧的情况下，QPE 的去除效率分别为 98.5%和 73%。进行了吸收光谱变化、pH 值效应和总有机碳（TOC）的变化研究。结果发现，所有吸收带随着辐照剂量的增加而减小，在施加 3 kGy 剂量后完全消失。在 QPE 的辐射降解中应用了三种 pH 值条件（pH=10、pH=6.2 和 pH=3），结果表明中性 pH 值下的去除效率最佳。有趣的是，在 3 kGy 时，TOC 的去除率达到 98%，表明实际上完全矿化。此外，分光光度分析支持 QPE 降解的拟一级动力学。得到的表观速率常数值约为 =(0.012±0.001) min。最后，通过气相色谱-质谱联用仪（GC/MS）鉴定出几种副产物，如 6-氯喹喔啉-2-醇、2-（4-羟基苯氧基）丙酸酯、1,4-对苯二酚、醌、4-氯-1,2-苯二酚和 1,2,4-苯三醇，这表明辐射过程始于分子的碎片化，涉及由水的辐射分解产生的羟基自由基。基于鉴定出的中间体，提出了 QPE 的降解机理图。
