Acta Chimica Sinica ›› 2022, Vol. 80 ›› Issue (8): 1106-1114.DOI: 10.6023/A22010044 Previous Articles     Next Articles



成受明, 周波*()   

  1. 四川大学建筑与环境学院 成都 610065
  • 投稿日期:2022-01-24 发布日期:2022-09-01
  • 通讯作者: 周波
  • 基金资助:
    国家自然科学基金(51878422); 成都市科技局项目(2021-YF05-00350-SN)

Molecular Insights into the Transformation Mechanisms of Dissolved Organic Matter Based on Ultrahigh Resolution Mass Spectrometry

Shouming Cheng, Bo Zhou()   

  1. College of Architecture & Environment, Sichuan University, Chengdu 610065
  • Received:2022-01-24 Published:2022-09-01
  • Contact: Bo Zhou
  • Supported by:
    National Natural Science Foundation of China(51878422); Science and Technology Bureau of Chengdu(2021-YF05-00350-SN)

In this study, the removal of dissolved organic matter (DOM) in pharmaceutical wastewater effluent by five treatment processes [including ultraviolet (UV), UV/H2O2, potassium persulfate (PS), carbon nano tubes (CNTs) and CNTs/PS] was investigated, which was characterized by excitation-emission matrix spectra spectroscopy (EEM), total dissolved carbon (TOC), zeta potential and dynamic light scattering analysis, while the transformation mechanism of DOM fractionations induced by PS, CNTs and CNTs/PS processes was further explored by ultra-high-resolution mass spectrometry (UPLC-Q-TOF-MS). The results suggested that the PS, CNTs and CNTs/PS processes proved to have the best treatment effect for the removal of DOM via EEM analysis, with TOC removal of 128, 204 and 243 mg/L, respectively. Zeta potential and dynamic light scattering analysis indicated that DOM molecules were removed by PS process through electrostatic polymerization and oxidation, and by CNTs process via adsorption, while CNTs/PS process degraded DOM by combining adsorption, electron transfer and the generation of strongly oxidizing singlet oxygen (1O2). Molecular characterization analysis demonstrated that the condensed aromatic compounds (76%) and proteins/lipids (65%) in DOM were the most vulnerable to PS attack, and the adsorption of CNTs was more effective for oxygenated compounds with lower levels of unsaturation (such as lignin, protein polypeptides and amino sugars (90%)), while the CNTs/PS process achieved indiscriminate degradation of various DOM molecules, which was a complement and enhancement to the separate CNT and PS treatment processes. In terms of different elemental compositions, the PS process had little effect on the elemental composition of the residual DOM molecules, while the CNTs and CNTs/PS processes showed a more obvious effect on the removal of CHON and CHONS molecules. Furthermore, by combining the quantitative distribution of chemical parameters of DOM molecules and linear fitting analysis, PS and CNTs/PS system had little effect on the distribution of chemical parameters of residual DOM molecules, while the adsorption of CNTs would lead to an increase in the average O/C, aromaticity index (AImod), double bond equivalence (DBE) and nominal oxidation state of carbon (NOSC) value of residual molecules, and the contribution of oxygen atoms to DBE. The results of this study provide important information for further understanding the behavior of DOM in the aquatic environment during various processes.

Key words: dissolved organic matter, potassium persulfate, carbon nanotubes, high resolution mass spectrum, molecular transformation