Effective oxidative degradation of coal gasification wastewater by ozonation: A process study

Zhiyong Yang; Yagang Zhang; Wenjuan Zhu; Xingjie Zan; Letao Zhang; Yanxia Liu

doi:10.1016/j.chemosphere.2020.126963

Effective oxidative degradation of coal gasification wastewater by ozonation: A process study

Chemosphere. 2020 Sep:255:126963. doi: 10.1016/j.chemosphere.2020.126963. Epub 2020 May 3.

Authors

Zhiyong Yang¹, Yagang Zhang², Wenjuan Zhu³, Xingjie Zan⁴, Letao Zhang⁵, Yanxia Liu⁶

Affiliations

¹ School of Materials and Energy, University of Electronic Science and Technology of China, Chengdu, 611731, China; Xinjiang Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Urumqi, 830011, China; University of Chinese Academy of Sciences, Beijing, 100049, China; Department of Chemical & Environmental Engineering, Xinjiang Institute of Engineering, Urumqi, 830023, China.
² School of Materials and Energy, University of Electronic Science and Technology of China, Chengdu, 611731, China; Xinjiang Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Urumqi, 830011, China; University of Chinese Academy of Sciences, Beijing, 100049, China; Department of Chemical & Environmental Engineering, Xinjiang Institute of Engineering, Urumqi, 830023, China. Electronic address: ygzhang@uestc.edu.cn.
³ Department of Chemical & Environmental Engineering, Xinjiang Institute of Engineering, Urumqi, 830023, China.
⁴ Xinjiang Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Urumqi, 830011, China; University of Chinese Academy of Sciences, Beijing, 100049, China. Electronic address: zanxj@ms.xjb.ac.cn.
⁵ Xinjiang Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Urumqi, 830011, China.
⁶ School of Materials and Energy, University of Electronic Science and Technology of China, Chengdu, 611731, China; Xinjiang Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Urumqi, 830011, China.

PMID: 32413797
DOI: 10.1016/j.chemosphere.2020.126963

Abstract

Coal gasification wastewater (CGW) has attracted considerable industrial attention because of its high toxicity and poor biodegradability. Ozonation is a promising process for CGW treatment. In this study, the effects of ozone concentration, pH, and ozonation time on CGW treatment were investigated. The results confirmed that CGW was degraded effectively and that the chemical oxygen demand (COD) was reduced from 1057 to 362 mgL^-1, utilizing 50 mgL^-1 ozone for 90 min. Further, the color of CGW changed from brown to clear and colorless, and the pH decreased from 8.5 to 4.7. Importantly, molds were observed in the oxidized CGW after 14 d at room temperature (23 ± 2 °C), indicating that CGW is significantly biodegradable by ozonation. The CGW components were extracted with three different organic solvents (chloroform, n-hexane, and benzene), and their compositions were analyzed by gas chromatography-mass spectrometry (GC-MS) before and after ozonation. The results proved that considerable amounts of highly toxic refractory compounds in CGW, such as phenolic compounds, polynuclear aromatic hydrocarbons (PAHs), and nitrogenous heterocyclic compounds (NHCs), were degraded to compounds that included olefins, carboxylic acids, and cycloalkanes, or minerals, which are relatively environmentally benign. Moreover, the number of substances in CGW decreased significantly from 127 to 74 after ozonation. Summarily, ozonation is a promising approach for the treatment of highly toxic refractory wastewater, such as CGW.

Keywords: Chemical oxygen demand; Coal gasification wastewater; Component; Degradation; Ozonation.

MeSH terms

Biodegradation, Environmental
Biological Oxygen Demand Analysis
Coal / analysis
Oxidation-Reduction
Oxidative Stress
Ozone / chemistry
Phenols / analysis
Polycyclic Aromatic Hydrocarbons / analysis
Waste Disposal, Fluid / methods*
Wastewater / chemistry

Substances

Coal
Phenols
Polycyclic Aromatic Hydrocarbons
Waste Water
Ozone