Low-molecular-weight dissolved organic nitrogen transformation behavior in concentrated leachate by O3 and OH: Partition, molecular insight, and potential precursor-product relationship. (15th December 2022)

• Record Type: Journal Article
• Authors: Wang, Hui; Xiang, Yan; Liu, Wei; Li, Jiyang; Zhu, Nanwen; Lou, Ziyang
• Is Part Of: Journal of environmental management. Volume 324(2022)
• Publication Date: 2022-12-15
• Subjects: Low-molecular-weight dissolved organic nitrogen -- Reactive oxygen species -- Concentrated leachate -- Molecular transformation -- Precursor-product pairs; Environmental policy -- Periodicals; Environmental management -- Periodicals; Environment -- Periodicals; Ecology -- Periodicals; 363.705
• DOI: 10.1016/j.jenvman.2022.116287
• Languages: English
• ISSNs: 0301-4797

Abstract

Abstract: Low-molecular-weight dissolved organic nitrogen (LMW-DON) is an emerging issue in concentrated leachate (CL). Ozonation is crucial to remove LMW-DON, but selectivity mechanisms of different reactive oxygen species were unknown. Here, reactions of O3 and OH with LMW-DON at different dosages were determined from composition, unsaturation/redox potential, and precursor-product relationship. The molecular weight of LMW-DON in CL presented a normal distribution and 76.5% was below 450 Da. LMW-DON with 400–1000 Da increased to 55.6%–66.7% and O/Cwa increased by over 40.0% due to electrophilic substitution of O3 . LMW-DON with <400 Da and 550–1000 Da were preferentially degraded by OH at the low and high O3 dosage, respectively. O3 preferred to remove lipid-like (69.1%), protein-like (58.2%), and amino sugars-like (72.8%) LMW-DON, whereas OH preferred to the refractory LMW-DON, such as carbohydrates-like (71.1%), lignin-like (49.6%), and tannins-like (72.5%) LMW-DON. Forty-three transformation reactions were quantified using mass difference analysis, and O3 preferred to oxygen addition (e.g., +2O) and conversed amino to nitro groups, and saturated LMW-DON increased via unsaturated bonds rupture. OH attacked the carbon groups (e.g., –CH2 ) and nitrogen groups (e.g., –NH3 +O, –NO2 +H). These findings provide molecular evidence for the selectivity of oxidants with LMW-DON and improve the ozonation application in wastewater treatment. Graphical abstract: Image 1 Highlights: Molecular transformation of LMW-DON oxidized by O3 and . OH in CL were determined. Forty-three pathways were quantified based on the precursor-product relationship. O3 preferred oxygen addition leading to increasing O/C and saturated degree of LMW-DON. 49.6%–72.5% refractory LMW-DON such as lignin-, tannins-like was degraded by . OH. OH has a stronger affinity for amine and nitro groups (e.g., –NH3 +O, –NO2 +H).