Analytical Department, Water Technology Center Karlsruhe (TZW), Karlsruher Str. 84, 76139 Karlsruhe, Germany.
Environ Sci Pollut Res Int. 2012 May;19(4):1107-18. doi: 10.1007/s11356-011-0618-x. Epub 2011 Oct 1.
The two artificial sweeteners cyclamate (CYC) and acesulfame (ACE) have been detected in wastewater and drinking water treatment plants. As in both facilities ozonation might be applied, it is important to find out if undesired oxidation products (OPs) are formed.
For the separation and detection of the OPs, several analytical techniques, including nuclear magnetic resonance experiments, were applied. In order to distinguish between direct ozone reaction and a radical mechanism, experiments were carried out at different pH values with and without scavenging OH radicals. Kinetic experiments were used for confirmation that the OPs are formed during short ozone contact time applied in waterworks. Samples from a waterworks using bank filtrate as raw water were analyzed in order to prove that the identified OPs are formed in real and full-scale ozone applications.
In the case of CYC, oxidation mainly occurs at the carbon atom, where the sulfonamide moiety is bound to the cyclohexyl ring. Consequently, amidosulfonic acid and cyclohexanone are formed as main OPs of CYC. When ozone reacts at another carbon atom of the ring a keto moiety is introduced into the CYC molecule. Acetic acid and the product ACE OP170, an anionic compound with m/z=170 and an aldehyde hydrate moiety, were identified as the main OPs for ACE. The observed reaction products suggest an ozone reaction according to the Criegee mechanism due to the presence of a C=C double bond. ACE OP170 was also detected after the ozonation unit of a full-scale drinking water treatment plant which uses surface water-influenced bank filtrate as raw water.
Acesulfame can be expected to be found in anthropogenic-influenced raw water used for drinking water production. However, when ACE OP170 is formed during ozonation, it is not expected to cause any problem for drinking water suppliers, because the primary findings suggest its removal in subsequent treatment steps, such as activated carbon filters.
人工甜味剂环己基氨基磺酸盐（CYC）和乙酰磺胺酸钾（ACE）已在废水和饮用水处理厂中被检出。由于这两种设施都可能应用臭氧氧化，因此确定是否形成了不良的氧化产物（OPs）非常重要。
为了分离和检测 OPs，应用了包括核磁共振实验在内的多种分析技术。为了区分直接臭氧反应和自由基机制，在不同 pH 值下进行了实验，并进行了 OH 自由基清除实验。动力学实验用于确认 OPs 是在水厂应用的短臭氧接触时间内形成的。使用以基滤水作为原水的水厂水样进行分析，以证明在实际和全规模臭氧应用中形成了所鉴定的 OPs。
在 CYC 的情况下，氧化主要发生在碳原子上，其中磺酰胺部分与环己基环结合。因此，氨基磺酸和环己酮是 CYC 的主要 OPs。当臭氧在环的另一个碳原子上反应时，酮部分被引入 CYC 分子中。鉴定出的 ACE 的主要 OPs 是乙酸和 ACE OP170，这是一种 m/z=170 的带醛水合部分的阴离子化合物。观察到的反应产物表明存在 C=C 双键，因此臭氧反应符合 Criegee 机制。ACE OP170 也在使用受地表水源影响的基滤水作为原水的全规模饮用水处理厂的臭氧处理单元后被检出。
在用于饮用水生产的受人为影响的原水中可以预期会发现乙酰磺胺酸钾。然而，当臭氧氧化过程中形成 ACE OP170 时，预计不会对饮用水供应商造成任何问题，因为主要发现表明它会在后续处理步骤（如活性炭过滤器）中被去除。
