Laboratory for Environmental Research, University of Nova Gorica, Nova Gorica, Slovenia.
Chemosphere. 2011 Oct;85(5):861-8. doi: 10.1016/j.chemosphere.2011.06.107. Epub 2011 Jul 28.
This work describes for the first time the photolytic and photocatalytic degradation of 6-chloronicotinic acid (6CNA) in double deionised water, which is a degradation product of neonicotinoid insecticides imidacloprid and acetamiprid, and it is known to appear in different environmental matrices. Photolytic experiments were performed with three UVA (ultraviolet A) polychromatic fluorescent lamps with broad maximum at 355 nm, while photocatalytic experiments were performed using immobilised titanium dioxide (TiO₂) on six glass slides in the spinning basket inside a photocatalytic quartz cell under similar irradiation conditions. Photolytic degradation revealed no change in concentration of 6CNA within 120 min of irradiation, while the photocatalytic degradation within 120 min, obeyed first-order kinetics. The observed disappearance rate constant was k=0.011 ± 0.001 min⁻¹ and t½ was 63.1 ± 5.5 min. Mineralisation rate was estimated through total organic carbon (TOC) and measurements revealed no carbon removal in case of photolysis after 120 min of exposure. However in photocatalytic experiments 46 ± 7% mineralisation was achieved within 120 min of irradiation. Nevertheless, the removal of total nitrogen (TN) was not observed across all experiments. Ion chromatographic analyses indicated transformation of chlorine atoms to chloride and increase of nitrate(V) ions only via photocatalytic experiments. Efficiency of selected advanced oxidation process (AOP) was investigated through toxicity assessment with Vibrio fischeri luminescent bacteria and revealed higher adverse effects of treated samples on bacteria following photocatalytic degradation in spite of the fact that higher mineralisation was achieved. New hydroxylated product generated in photocatalytic experiments with TiO₂, was confirmed with liquid chromatography-electro spray ionisation mass spectrometry (LC-ESI-MS/MS) analyses, gas chromatography-mass spectrometry (GC-MS) and nuclear magnetic resonance spectroscopy (¹H NMR).
本工作首次描述了 6-氯烟碱酸（6CNA）在双去离子水中的光解和光催化降解，6CNA 是新烟碱类杀虫剂吡虫啉和噻虫胺的降解产物，已知其出现在不同的环境基质中。光解实验使用三个最大发射波长为 355nm 的 UVA（紫外线 A）多色荧光灯进行，而光催化实验则使用固定在旋转篮内的六片玻璃载玻片上的二氧化钛（TiO₂）在类似的辐照条件下在光催化石英池中进行。光解降解在 120 分钟的辐照时间内未观察到 6CNA 浓度的变化，而光催化降解在 120 分钟内遵循一级动力学。观察到的消失速率常数为 k=0.011±0.001min⁻¹，t½为 63.1±5.5min。通过总有机碳（TOC）估计矿化率，结果表明在 120 分钟的暴露时间内，光解后没有碳去除。然而，在光催化实验中，在 120 分钟的辐照时间内实现了 46±7%的矿化。尽管如此，在所有实验中都没有观察到总氮（TN）的去除。离子色谱分析表明，仅通过光催化实验，氯原子转化为氯离子和硝酸盐（V）离子增加。通过发光细菌 Vibrio fischeri 的毒性评估研究了选定的高级氧化工艺（AOP）的效率，结果表明，尽管实现了更高的矿化，但在光催化降解后，处理样品对细菌的不良影响更大。通过液相色谱-电喷雾电离质谱联用（LC-ESI-MS/MS）分析、气相色谱-质谱（GC-MS）和核磁共振波谱（¹H NMR）证实了在光催化实验中用 TiO₂生成的新羟基化产物。
