Oppenländer Thomas, Walddörfer Carsten, Burgbacher Jens, Kiermeier Martin, Lachner Klaus, Weinschrott Helga
Department of Process Engineering, University of Applied Sciences Furtwangen, Jakob-Kienzle-Strasse 17, D-78054 Villingen-Schwenningen, Germany.
Chemosphere. 2005 Jul;60(3):302-9. doi: 10.1016/j.chemosphere.2004.12.037.
Xenon excimer (Xe2*) lamps can be used for the oxidation and mineralization of organic compounds in aqueous solution. This vacuum-ultraviolet (VUV) photochemical method is mainly based on the photochemically initiated homolysis of water that produces hydrogen atoms and hydroxyl radicals. The efficiency of substrate oxidation and mineralization is limited markedly due to the high absorbance of water at the emission maximum of the Xe2* lamp (lambda(max)=172 nm). This photochemical condition generates an extreme heterogeneity between the irradiated volume V(irr) and the non-irradiated ("dark") bulk solution. During VUV-initiated photomineralization of organic substrates, the fast scavenging of hydrogen atoms and of carbon-centered radicals by dissolved molecular oxygen produces a permanent oxygen deficit within V(irr) and adjacent compartments. Hence, at a constant photon flux the concentration of dissolved molecular oxygen within the zones of photo and thermal radical reactions limits the rate of mineralization, i.e. the rate of TOC diminution. Thus, a simple and convenient technique is presented that overcomes this limitation by injection of molecular oxygen (or air) into the irradiated volume by use of a ceramic oxygenator (aerator). The tube oxygenator was centered axially within the xenon excimer flow-through lamp. Consequently, the oxygen or air bubbles enhanced the transfer of dissolved molecular oxygen into the VUV-irradiated volume leading to an increased rate of mineralization of organic model compounds, e.g. 1-heptanol, benzoic acid and potassium hydrogen phthalate.
氙准分子（Xe2*）灯可用于水溶液中有机化合物的氧化和矿化。这种真空紫外（VUV）光化学方法主要基于光化学引发的水的均裂，产生氢原子和羟基自由基。由于水在Xe2*灯发射最大值（λ(max)=172 nm）处的高吸光度，底物氧化和矿化的效率受到显著限制。这种光化学条件在照射体积V(irr)和未照射的（“暗”）本体溶液之间产生了极大的不均匀性。在VUV引发的有机底物光矿化过程中，溶解的分子氧对氢原子和以碳为中心的自由基的快速清除在V(irr)和相邻隔室内产生了永久性的氧亏缺。因此，在恒定光子通量下，光和热自由基反应区域内溶解分子氧的浓度限制了矿化速率，即总有机碳（TOC）减少的速率。因此，本文提出了一种简单方便的技术，通过使用陶瓷充氧器（曝气器）将分子氧（或空气）注入照射体积来克服这一限制。管式充氧器轴向位于氙准分子流通灯的中心。因此，氧气或空气泡增强了溶解分子氧向VUV照射体积的转移，导致有机模型化合物（如1-庚醇、苯甲酸和邻苯二甲酸氢钾）的矿化速率增加。
