Decomposition Characteristics of Organics Dissolved in Water under Irradiation of Diffuse Light Including Far UV Light and Excimer Light

根据超纯水循环使用清洗半导体元件的工艺发展研究，我们首先研究了一种利用低压汞灯照射远紫外光(紫外线)185 nm和紫外光354 nm来分解微量溶解于无氧水中的有机物的工艺的可能性。其次，我们尝试通过将上述结果与远紫外172 nm准分子光照射的结果进行比较，来评估远紫外光的效果。以甲醇为起始反应物，即使在无氧条件下，TOC也能完全分解。与氧存在下的辐射相比，有机物的直接分解占主导地位，其中羟基自由基起着重要作用。第三，我们旨在模拟氧存在下TOC的远紫外光降解动力学，这是一种远(真空)紫外光氧化过程，因为从实用的角度来看，定量解释氧存在下的分解特性也很重要。如本报告所述，通过使用在助学金下分别购买的总有机碳分析仪和准分子灯，积累了准确的数据；特别是用准分子灯清楚地评估了远紫外光的唯一效果。现在正在用基于控制甲醇、甲醛和甲酸分解生成过氧化氢的化学计量方程的反应速率方程来模拟观察到的分解行为。结果将很快公布。

In line with the research on process developments of recycle use of ultrapure water for cleaning semiconductor elements, we firstly examined the possibilities of a process which could decompose a trace amount of organics dissolved in oxygen-free water by irradiating far UV (ultaviolet) 185nm light, and UV 354nm light with a low-pressure mercury lamp. We secondly tried evaluating the effect of far UV light by comparing the above-mentioned results to the one with far UV 172nm excimer light irradiation. Complete decomposition of TOC has been achieved even in the absence of oxygen with methanol as an initial reactant. Direct decomposition of organics is dominant here in comparison with the case of irradiation in the presence of oxygen where a hydroxyl radical plays an important role.We thirdly aimed at modelling kinetics of far UV degradation of TOC in the presence of oxygen, a far (vacuum) UV oxidation process, because a quantitative interpretation of decomposition characteristics in the presence of oxygen is also important from a practical point of view. As described in the present report, precise data have been accumulated with good use of a TOC analyzer and an excimer lamp respectively purchased under the grant-in-aid ; especially the sole effect of far UV light was clearly evaluated with the excimer lamp. Simulation of the decomposition hehavior observed is now being conducted with reaction-rate equations based on the stoichiometric equations governing methanol, formaldehyde, and formic acid decomposition to form hydrogen peroxide. Results will soon be reported.