Humic acid (HA) is a typical refractory organic matter, widely existing in natural water and many types of wastewaters. In this study, Bi/SnO2 composites were synthesized by a simple one-step hydrothermal method for photocatalytic degradation of HA. Due to the surface plasmon resonance (SPR) effect of Bi, the light absorption of Bi/SnO2 composites expands from UV to visible light compared to pure SnO2. Under visible light irradiation for 120 min, the UV254 removal reached 93.58 %, color number (CN) removal reached 94.41 %. The degradation rate constant of Bi/SnO2 (0.0178 min−1) is 14.83 times higher than that of SnO2 (0.0012 min−1), indicating the superior photocatalytic degradation efficiency of Bi/SnO2 composites. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) was found that photocatalysis mainly degraded most CHO-containing organic matter and reduced the amount of organic matter (from 7240 to 3886). The molecular number of organic compounds with m/z of 400–500 and 500–600 exhibited a significant decrease, specifically by 1052 and 770, respectively. This observation suggests that the photocatalytic process effectively eliminates low and moderate molecular weight organics. The molecular number, aromaticity and molecular weight of dissolved organic matter (DOM) were reduced mainly by carboxylic acid reaction, dealkylation reaction and oxygen addition reaction.

中文翻译：

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Bi/SnO2 的合成及其机理在可见光下增强光催化降解腐植酸活性


腐植酸 （HA） 是一种典型的难降解有机物，广泛存在于天然水和多种类型的废水中。本研究采用简单的一步水热法合成了 Bi/SnO2 复合材料，用于光催化降解 HA。由于 Bi 的表面等离子体共振 （SPR） 效应，与纯 SnO2 相比，Bi/SnO2 复合材料的光吸收范围从紫外扩展到可见光。在可见光照射 120 min 下，UV254 去除率达到 93.58 %，色数 （CN） 去除率达到 94.41 %。Bi/SnO2 的降解速率常数 （0.0178 min-1） 比 SnO2 （0.0012 min-1） 高 14.83 倍，表明 Bi/SnO2 复合材料具有优异的光催化降解效率。傅里叶变换离子回旋共振质谱 （FT-ICR MS） 发现，光催化主要降解大多数含 CHO 的有机物，并减少有机物的数量 （从 7240 减少到 3886）。m/z 为 400-500 和 500-600 的有机化合物的分子量显著减少，特别是分别减少了 1052 和 770。这一观察结果表明，光催化过程有效地消除了低分子量和中等分子量的有机物。溶解有机物 （DOM） 的分子数、芳香性和分子量主要通过羧酸反应、脱烷基化反应和氧加成反应降低。