Abstract

Titanium dioxide, one of the most important photocatalysts for the oxidation of compounds dissolved in water, is active only under ultraviolet irradiation and inactive in the visible spectral region due to its broad bandgap. A promising strategy for the creation of active TiO₂ samples able to efficiently utilize visible sunlight and thereby to essentially decrease the cost of the photocatalytic treatment of natural and waste water is the introduction of several dopants. The efficiency of nitrogen doped and nitrogen and iron ion codoped titania samples synthesized by the sol-gel method with a bandgap narrowed to 2.59–2.99 eV in the photocatalytic destruction of humic acid (HA) in water (C = 55–60 mg/dm³) with atmospheric oxygen and hydrogen peroxide was studied depending on pH and a radiation source: an SVD-120 mercury quartz lamp (λ > 200 nm) or a GE CMG70 metal halide lamp (λ > 360 nm). The efficiency of doped TiO₂ samples in the photocatalytic oxidation of aqueous HA solutions depended on the iron content (0–1% of Fe), the used oxidant, pH of the medium, and the irradiation mode. A much higher degree of HA destruction was attained in an acidic medium (pH₀ 2.4) as compared to a neutral medium (pH₀ 7) in both irradiation modes. The application of hydrogen peroxide increased the degree of photocatalytic HA mineralization in the presence of all the synthesized samples in both irradiation modes as compared to the oxidation with dissolved oxygen and essentially approached the efficiency of synthesized photocatalysts to standard Degussa P-25 TiO₂. On the whole, N-TiO₂ was most active among the synthesized photocatalysts. No clear dependence of the HA destruction degree on the Fe content in the samples (Fe,N-TiO₂; 0.25–1.0%) were established at studied destruction parameters. In general, the codoped samples (Fe,N-TiO₂) essentially inhibited HA destruction and, in a neutral medium, the inhibiting effect became stronger with increasing iron content in a sample in both irradiation modes. It seems probable that the recombination of photogenerated electron–hole charge carriers was intensified due to the selected method of N-TiO₂ codoping with Fe³⁺ ions or the range of dopant concentrations.

中文翻译：

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比较不同辐照模式下 (N,Fe) 掺杂二氧化钛样品在氧气和过氧化氢中光催化腐殖酸降解的效率

摘要

二氧化钛是用于氧化溶解在水中的化合物的最重要的光催化剂之一，由于其宽带隙，它仅在紫外线照射下才具有活性，而在可见光谱区域内则无活性。_{制备能够有效利用可见光的活性 TiO 2}样品并因此从根本上降低天然水和废水的光催化处理成本的有前景的策略是引入几种掺杂剂。溶胶-凝胶法合成的氮掺杂和氮和铁离子共掺杂的二氧化钛样品在光催化破坏水中腐殖酸 (HA) 的效率 ( C = 55-60 mg/dm ) ³) 对大气中的氧气和过氧化氢进行研究，具体取决于 pH 值和辐射源：SVD-120 汞石英灯 (λ > 200 nm) 或 GE CMG70 金属卤化物灯 (λ > 360 nm)。掺杂 TiO ₂样品在 HA 水溶液的光催化氧化中的效率取决于铁含量（Fe 的 0-1%）、使用的氧化剂、介质的 pH 值和辐照模式。_与中性介质（pH ₀7) 在两种辐照模式下。与溶解氧氧化相比，过氧化氢的应用在所有合成样品存在下以两种辐照模式增加了光催化 HA 矿化的程度，并且基本上接近标准 Degussa P-25 TiO ₂的合成光催化剂的效率。总体而言，在合成的光催化剂中，N-TiO ₂的活性最高。在研究的破坏参数下，HA 破坏程度对样品中的 Fe 含量（Fe,N-TiO ₂；0.25-1.0%）没有明确的依赖性。一般来说，共掺杂样品（Fe,N-TiO ₂) 基本上抑制了 HA 的破坏，并且在中性介质中，在两种辐照模式下，随着样品中铁含量的增加，抑制作用变得更强。由于选择的 N-TiO ₂与 Fe ³⁺离子共掺杂的方法或掺杂剂浓度的范围，光生电子-空穴电荷载流子的复合似乎可能得到了加强。