Department of Chemistry, Carnegie Mellon University , 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, United States.
Institute for the Environment, Brunel University , Halsbury Building (130), Kingston Lane, Uxbridge, Middlesex, UB8 3PH, United Kingdom.
Environ Sci Technol. 2016 May 17;50(10):5261-8. doi: 10.1021/acs.est.5b05518. Epub 2016 May 3.
The extremely persistent molluscicide, metaldehyde, widely used on farms and gardens, is often detected in drinking water sources of various countries at concentrations of regulatory concern. Metaldehyde contamination restricts treatment options. Conventional technologies for remediating dilute organics in drinking water, activated carbon, and ozone, are insufficiently effective against metaldehyde. Some treatment plants have resorted to effective, but more costly UV/H2O2. Here we have examined if TAML/H2O2 can decompose metaldehyde under laboratory conditions to guide development of a better real world option. TAML/H2O2 slowly degrades metaldehyde to acetaldehyde and acetic acid. Nuclear magnetic resonance spectroscopy ((1)H NMR) was used to monitor the degradation-the technique requires a high metaldehyde concentration (60 ppm). Within the pH range of 6.5-9, the reaction rate is greatest at pH 7. Under optimum conditions, one aliquot of TAML 1a (400 nM) catalyzed 5% degradation over 10 h with a turnover number of 40. Five sequential TAML aliquots (2 μM overall) effected a 31% removal over 60 h. TAML/H2O2 degraded metaldehyde steadily over many hours, highlighting an important long-service property. The observation of metaldehyde decomposition under mild conditions provides a further indication that TAML catalysis holds promise for advancing water treatment. These results have turned our attention to more aggressive TAML activators in development, which we expect will advance the observed technical performance.
在农场和花园中广泛使用的具有极强持久性的杀螺剂——聚乙醛，常被检测到在各国的饮用水源中，其浓度达到了监管关注的水平。聚乙醛污染限制了处理方案的选择。用于处理饮用水中稀释有机物的常规技术，如活性炭和臭氧，对聚乙醛的效果不够理想。一些处理厂已经转而使用效果更好但成本更高的 UV/H2O2。在这里，我们研究了 TAML/H2O2 是否可以在实验室条件下分解聚乙醛，以指导开发更好的实际选择。TAML/H2O2 可以缓慢地将聚乙醛分解为乙醛和乙酸。我们使用核磁共振波谱 ((1)H NMR) 来监测降解过程——该技术需要高浓度的聚乙醛（60ppm）。在 pH 值为 6.5-9 的范围内，反应速率在 pH 值为 7 时最大。在最佳条件下，一份 TAML 1a（400nM）在 10 小时内催化了 5%的降解，周转率为 40。五个连续的 TAML 等分试样（总浓度为 2μM）在 60 小时内去除了 31%。TAML/H2O2 可以在数小时内稳定地降解聚乙醛，这突出了其重要的长期服务特性。在温和条件下观察到聚乙醛的分解进一步表明，TAML 催化具有推进水处理的潜力。这些结果引起了我们对正在开发的更具攻击性的 TAML 激活剂的关注，我们预计这将提高观察到的技术性能。
