Harbin Institute of Technology Shenzhen Graduate School, Shenzhen Key Laboratory of Water Resource Utilization and Environmental Pollution Control, Shenzhen 518055, PR China.
Harbin Institute of Technology Shenzhen Graduate School, Shenzhen Key Laboratory of Water Resource Utilization and Environmental Pollution Control, Shenzhen 518055, PR China.
Sci Total Environ. 2017 Dec 31;607-608:541-548. doi: 10.1016/j.scitotenv.2017.06.197. Epub 2017 Jul 27.
As one of the most reactive species, hydrated electron (e) is promising for reductive decomposition of recalcitrant organic pollutants, such as perfluorooctane sulfonate (PFOS). In this study, PFOS decomposition using a vacuum ultraviolet (VUV)/sulfite system was systematically investigated in comparison with sole VUV and ultraviolet (UV)/sulfite systems. A fast and nearly complete (97.3%) PFOS decomposition was observed within 4h from its initial concentration of 37.2μM in the VUV/sulfite system. The observed rate constant (k) for PFOS decomposition in the studied system was 0.87±0.0060h, which was nearly 7.5 and 2 folds faster than that in sole VUV and UV/sulfite systems, respectively. Compared to previously studied UV/sulfite system, VUV/sulfite system enhanced PFOS decomposition in both weak acidic and alkaline pH conditions. In weak acidic condition (pH6.0), PFOS predominantly decomposed via direct VUV photolysis, whereas in alkaline condition (pH>9.0), PFOS decomposition was mainly induced by e generated from both sulfite and VUV photolytic reactions. At a fixed initial solution pH (pH10.0), PFOS decomposition kinetics showed a positive linear dependence with sulfite dosage. The co-presence of humic acid (HA) and NO obviously suppressed PFOS decomposition, whereas HCO showed marginal inhibition. A few amount of short chain perfluorocarboxylic acids (PFCAs) were detected in PFOS decomposition process, and a high defluorination efficiency (75.4%) was achieved. These results suggested most fluorine atoms in PFOS molecule ultimately mineralized into fluoride ions, and the mechanisms for PFOS decomposition in the VUV/sulfite system were proposed.
作为最具反应性的物种之一，水合电子 (e) 有望用于还原分解难降解的有机污染物，如全氟辛烷磺酸 (PFOS)。在这项研究中，与单独的 VUV 和紫外线 (UV)/亚硫酸盐系统相比，系统地研究了真空紫外线 (VUV)/亚硫酸盐系统中 PFOS 的分解。在 VUV/亚硫酸盐系统中，初始浓度为 37.2μM 的 PFOS 在 4 小时内即可快速且几乎完全 (97.3%) 分解。在研究的系统中，PFOS 分解的观测速率常数 (k) 为 0.87±0.0060h，分别比单独的 VUV 和 UV/亚硫酸盐系统快近 7.5 和 2 倍。与之前研究的 UV/亚硫酸盐系统相比，VUV/亚硫酸盐系统在弱酸性和碱性 pH 条件下均增强了 PFOS 的分解。在弱酸性条件 (pH6.0) 下，PFOS 主要通过直接 VUV 光解分解，而在碱性条件 (pH>9.0) 下，PFOS 分解主要由亚硫酸盐和 VUV 光解反应产生的 e 引发。在固定初始溶液 pH (pH10.0) 下，PFOS 分解动力学与亚硫酸盐用量呈正线性关系。腐殖酸 (HA) 和 NO 的共存明显抑制了 PFOS 的分解，而 HCO 表现出轻微的抑制作用。在 PFOS 分解过程中检测到少量短链全氟羧酸 (PFCAs)，并实现了高脱氟效率 (75.4%)。这些结果表明，PFOS 分子中的大部分氟原子最终矿化为氟离子，并提出了 VUV/亚硫酸盐系统中 PFOS 分解的机制。
