Abstract：In order to explore the transformation and fate of soil NH4+ in the thermally activated PS oxidation process, this study used soil samples collected from Jiangsu and Hebei provinces with different soil organic matter content and NH4+ concentration to conduct experiments, and systematically investigated effects of persulfate (PS) concentration, the addition of NH4+, and reaction time on the formation of nitro by-products. Results show that soil NH4+ could be transformed to nitrated byproducts, including 3-nitrophenol, 4-nitrophenol, 2-hydroxy-5-nitrobenzoic acid, 4-hydroxy-3-nitrobenzoic acid, 2, 4-dinitrophenol, etc. The formation of nitro by-products increased first and then decreased with reaction time. An increased in PS dose would promote the formation of nitro by-products, and the yields of mono-nitrophenols and hydroxy-mono-nitrobenzoic acids reached the maximum after 12h reaction at 30mmol/kg PS dose. However, nitrated byproducts were degraded at higher PS dose. Note that sulfate radicals (SO4·-) played a key role in the nitration process by oxidizing NH4+ to form aminyl radicals (·NH2), and then underwent a series of free radical chain reactions to form nitrogen dioxide radicals (NO2·). Besides, phenol moieties in soil organic matter served as the main reactive sites for SO4·- attack, leading to the formation of phenoxy radicals, which further combined with NO2· to form nitro by-products. NOM is everywhere and NH4+ is ubiquitous in the environment. Thus, the formation of nitro by-products will be widespread when PS is applied for contaminated soil and groundwater remediation, which should be taken into consideration when evaluating the feasibility of this technology. This study reveals that the presence of soil NH4+ in activated PS oxidation processes could induce the nitration of NOM and the formation of nitrophenolic by-products.
杨培增, 岳泓伸, 季跃飞, 陆隽鹤. 土壤铵氮在热活化过硫酸盐氧化过程中的转化[J]. 中国环境科学, 2022, 42(1): 267-275.
YANG Pei-zeng, YUE Hong-shen, JI Yue-fei, LU Jun-he. Transformation of soil ammonium nitrogen in the process of thermally activated persulfate oxidation. CHINA ENVIRONMENTAL SCIENCECE, 2022, 42(1): 267-275.
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