腐殖质及其模型化合物的H2O2光化学生成研究

在模拟太阳光下研究了多种腐殖质及其模型化合物的过氧化氢（H₂O₂）生成动力学，并对其生成机制进行了探讨.结果表明不同来源或不同形式的腐殖质在模拟太阳光照射下均能产生H₂O₂.不同腐殖质生成H₂O₂速率差异不大，范围为6.379~15.784nmol/（L·min），腐殖酸生成H₂O₂速率略快于富里酸.对于腐殖质模型化合物，邻苯二酚、间苯二酚、对苯二酚、苯醌、邻茴香胺、对茴香胺、水杨酸和2，6-二甲氧基-1，4-苯醌等8种模型化合物没有产生明显的H₂O₂，而藜芦醇、对氨基苯甲酸、3，5-二羟基苯甲酸（DHBA）、2，5-二羟基-1，4-苯醌、苯酚、苯甲酸和苯胺等7种化合物均可检测到H₂O₂产生.但其产生H₂O₂的速率差异较大，相差1~2个数量级，生成H₂O₂速率最快的化合物为2，5-二羟基-1，4-苯醌和DHBA，较慢的为苯酚、苯甲酸和对氨基苯甲酸.基于腐殖质生成H₂O₂机制，推测典型模型化合物DHBA的H₂O₂生成机制可能为光照条件下该化合物跃迁为单重激发态，该激发态发生分子内电子转移，生成还原性自由基中间体，该中间体和O₂反应，生成了超氧负离子（O₂·^-），随后与水中H⁺反应生成了H₂O₂.

Hydrogen peroxide photoproduction by humic substances and their model compounds

The present study systematically investigated H₂O₂ generation kinetics and potential mechanism from irradiated humic substances (HS) and their model compounds under simulated sunlight. Our results indicated that all the selected HS with different sources or forms can produce H₂O₂ under irradiation, and no significant difference was observed between them, with the generation rate ranging from 6.379 to 15.784nmol/(L·min). The H₂O₂ generation rate from humic acid (HA) was slightly faster than that from fulvic acid (FA). In the case of humus model compounds, 7compounds including veratryl alcohol, p-aminobenzoic acid, 3,5-dihydroxybenzoic acid (DHBA), 2,5-dihydroxy-1,4-benzoquinone, phenol, benzoic acid and aniline could produce detectable H₂O₂, while other compounds including catechol, resorcinol, hydroquinone, quinone, o-anisidine, p-anisidine, salicylic acid and 2,6-dimethoxy-1,4-benzoquinone can't. Nevertheless, the H₂O₂ generation rate from the model compounds varies from each other, with one or two orders of magnitude. Among them, 2,5-dihydroxyl-1,4-benquione and DHBA exhibited the highest H₂O₂ yields, while phenol, benzoic and p-aminobenzoic acid showed a relative low H₂O₂ generation potential. Based on the generation mechanism of H₂O₂ from HS, a possible H₂O₂ formation mechanism from a typical model compound, i.e. DHBA, was proposed. DHBA was believed to excite to a singlet state, after an intramolecular electron transfer process, giving a reducing intermediate. The intermediate could further react with O₂ to form O₂·^- and subsequently generate H₂O₂.