Comparison on molecular transformation of dissolved organic matter during Fenton and activated carbon adsorption processes for chemical cleaning wastewater treatment

• Published in: Separation and purification technology Vol. 344; p. 127226
• Main Authors: Zhao, Xiaodan, Huang, Zhuojun, Sun, Haosen, Zhao, Qiqi, Huang, Zhanghe, Zhang, Chun, Wang, Yang, Yang, Chunyan, Zhou, Zhen
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 20.09.2024
• Subjects: Activated carbon adsorption; Chemical cleaning wastewater; Dissolved organic matter; Fenton oxidation; FT-ICR MS; Chemical cleaning wastewater; Dissolved organic matter; FT-ICR MS; Activated carbon adsorption; Fenton oxidation
• ISSN: 1383-5866; 1873-3794
• DOI: 10.1016/j.seppur.2024.127226

[Display omitted] •Dissolved organic matter (DOM) was removed from chemical cleaning wastewater (CCW).•Molecular insight into DOM transformation was elucidated in Fenton and PAC processes.•PAC adsorption was efficient in removing aromatic compounds compared to Fenton.•Carboxylic-rich alicyclic molecules/lignin dominated by CHON were produced in Fenton.•Aliphatic compounds in CCW were resistant to PAC adsorption and Fenton oxidation. This study employed Fenton oxidation and powdered activated carbon (PAC) adsorption processes for the removal of recalcitrant dissolved organic matter (DOM) in chemical cleaning wastewater (CCW) to meet discharge standards. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) was used to identify resistant compounds and investigate the transformation characteristics of DOM. CCW mainly contained surfactant exhibiting heteroatom-rich characteristics, and both processes exhibited effective DOM removal but distinct selectivity towards different subclasses of formulas. PAC adsorption significantly decreased the number of DOM compounds and more effective in aromatic compounds than Fenton oxidation. The aliphatic compounds (AImod ≤ 0.5, 1.5 ≤ H/C ≤ 2.0) predominantly with saturated and reduced states were resistant to PAC adsorption, and particularly a specific CHONSP formula was the predominant contributor to residual DOM in the effluent. In contrast, Fenton oxidation degraded most substances in the CCW except for a few saturated and reduced compounds primarily consisting of CHO, resulting in an increase in DOM number. Two unsaturated subclasses, carboxylic-rich alicyclic molecules/lignin-like structures (primarily CHON) and carbohydrates (primarily CHONP and CHONSP), were prominently produced after Fenton oxidation. The major mechanisms governing Fenton oxidation of surfactant in CCW primarily involved dealkylation (25.2 %), oxygen addition (21.2 %), and decarboxylation (19.8 %). Given the unique removal preferences and resistance observed in Fenton and PAC processes, a combination approach could be explored in the future to achieve advanced overall performance.