Heterogeneous Photocatalytic Oxidation of Nitrogen Oxides and Sulfur Dioxide in Aqueous Solutions in Connecton with Environmental Pollution

研究了环境空气中<NO_2^->的多相光催化氧化与酸雨形成的关系。典型的实验包括<NaNO_2>用氙灯照射石英管中的水溶液。该水溶液含有保持在超声波悬浮液中的半导体粉末。<O_2>向水性悬浮液中鼓泡。在光照条件下，在某些半导体粉末存在下，&lt;NO_2^-&gt;被定量氧化为&lt;NO_3^-&gt;<O_2>。本反应中的光活性半导体粉末<TiO_2>为ZnO<Ag_2O>、PbO、<Bi_2O_3>CdS，并研究了它们对水中&lt;SO_3^（2-）&gt;的光氧化作用。在光催化过程中，&lt;SO_3^（2-）&gt;被氧化为&lt;SO_4^（2-）&gt;。<TiO_2>并且<Fe_2O_3>对于该反应是极其活性的光催化剂。在光照条件下，精确测定了（ZnO）、金红石和ZnO悬浮液中&lt;NO_2^-&gt;的非均相光氧化速率<TiO_2><TiO_2>。该反应对&lt;NO_2^-&gt;浓度呈零级反应。在假设的环境条件下，估算了云水液滴中&lt;NO_2^-&gt;的光氧化速率。当云水含量为0.2 g &lt;m^（-3）&gt;时，降水速率为11% &lt;h^（-1）&gt;。

Heterogeneous photocatalytic oxidation of <NO_2^-> was studied in connection with acid rain formation in environmental air. Typical experiments consisted of illuminating <NaNO_2> aqueous solution in a quartz tube with a xenon lamp. The aqueous solution contained semiconductor powders kept in suspension supersonically. <O_2> was bubbled into the aqueous suspensions. <NO_2^-> was quantitatively oxidized to <NO_3^-> with <O_2> under illumination in the presence of some semiconductor powders. Photoactive semiconductor powders in this reaction are <TiO_2> , ZnO, <Ag_2O> , PbO, <Bi_2O_3> , and CdS.Photooxidation of <SO_3^(2-)> in water was also studied in the presence of some semiconductor powders. <SO_3^(2-)> is oxidized to <SO_4^(2-)> in the photocatalytic process. <TiO_2> and <Fe_2O_3> are extremely active photocatalyst for this reaction. Rates of heterogeneous photooxidation of <NO_2^-> were precisely measured in aqueous suspension of <TiO_2> (anatase), <TiO_2> (rutile), and ZnO under illumination. The reaction proceeds in zero order with respect to <NO_2^-> concentration. The rate of photooxidation of <NO_2^-> in cloud water droplets was estimated with hypothetical environmental conditions. The rate amounts to 11% <h^(-1)> for cloud water content of 0.2 g <m^(-3)> .