College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, China.
College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, China.
Water Res. 2017 Oct 15;123:249-257. doi: 10.1016/j.watres.2017.06.081. Epub 2017 Jun 28.
As promising in-situ chemical oxidation (ISCO) technologies, sulfate radical-based advanced oxidation processes (SR-AOPs) are applied in wastewater treatment and groundwater remediation in recent years. In this contribution, we report for the first time that, thermally activated persulfate oxidation of phenol in the presence of nitrite (NO), an anion widely present in natural waters, could lead to the formation of nitrated by-products including 2-nitrophenol (2-NP), 4-nitrophenol (4-NP), 2,4-dinitrophenol (2,4-DNP), and 2,6-dinitrophenol (2,6-DNP). Nitrogen dioxide radical (NO), arising from SO scavenging by NO, was proposed to be involved in the formation of nitrophenols as a nitrating agent. It was observed that nitrophenols accounted for approximately 70% of the phenol transformed under reaction conditions of [NO] = 200 μM, [PS] = 2 mM and temperature of 50 °C. Increasing the concentration of NO remarkably enhanced the formation of nitrophenols but did not affect the transformation rate of phenol significantly. The degradation of phenol and the formation of nitrophenols were significantly influenced by persulfate dosage, solution pH and natural organic matter (NOM). Further studies on the degradation of other phenolic compounds, including 4-chlorophenol (4-CP), 4-hydroxybenzoic acid (4-HBA), and acetaminophen (ATP), verified the formation of their corresponding nitrated by-products as well. Therefore, formation of nitrated by-products is probably a common but overlooked phenomenon during SO-based oxidation of phenolic compounds in the presence of NO. Nitroaromatic compounds are well known for their carcinogenicity, mutagenicity and genotoxicity, and are potentially persistent in the environment. The formation of nitrated organic by-products in SR-AOPs should be carefully scrutinized, and risk assessment should be carried out to assess possible health and ecological impacts.
作为有前景的原位化学氧化 (ISCO) 技术，基于硫酸根自由基的高级氧化工艺 (SR-AOPs) 近年来被应用于废水处理和地下水修复。在本研究中，我们首次报道了在亚硝酸盐 (NO) 存在的情况下，热激活过硫酸盐氧化苯酚，NO 是一种在天然水中广泛存在的阴离子，可能导致形成硝化副产物，包括 2-硝基苯酚 (2-NP)、4-硝基苯酚 (4-NP)、2,4-二硝基苯酚 (2,4-DNP) 和 2,6-二硝基苯酚 (2,6-DNP)。提出了由 SO 与 NO 反应生成的二氧化氮自由基 (NO) 作为硝化剂参与了硝基苯酚的形成。结果表明，在 [NO] = 200 μM、[PS] = 2 mM 和 50°C 的反应条件下，约有 70%的苯酚转化为硝基苯酚。增加 NO 的浓度显著提高了硝基苯酚的生成量，但对苯酚的转化速率影响不大。过硫酸盐用量、溶液 pH 值和天然有机物 (NOM) 显著影响了苯酚的降解和硝基苯酚的生成。对其他酚类化合物（包括 4-氯苯酚 (4-CP)、4-羟基苯甲酸 (4-HBA) 和对乙酰氨基酚 (ATP)）的降解研究也验证了它们相应的硝化副产物的形成。因此，在存在 NO 的情况下，SO 基氧化酚类化合物时形成硝化副产物可能是一种常见但被忽视的现象。硝基芳香族化合物以其致癌性、致突变性和遗传毒性而闻名，并且在环境中可能具有持久性。SR-AOPs 中形成的硝化有机副产物应仔细审查，并进行风险评估，以评估可能对健康和生态造成的影响。
