Insights into the synergetic mechanism of a combined vis-RGO/TiO2/peroxodisulfate system for the degradation of PPCPs: Kinetics, environmental factors and products

Ping Chen; Qianxin Zhang; Lingzhi Shen; Ruobai Li; Cuiwen Tan; Tiansheng Chen; Haijin Liu; Yang Liu; Zongwei Cai; Guoguang Liu; Wenying Lv

doi:10.1016/j.chemosphere.2018.10.096

Insights into the synergetic mechanism of a combined vis-RGO/TiO₂/peroxodisulfate system for the degradation of PPCPs: Kinetics, environmental factors and products

Chemosphere. 2019 Feb:216:341-351. doi: 10.1016/j.chemosphere.2018.10.096. Epub 2018 Oct 22.

Authors

Ping Chen¹, Qianxin Zhang², Lingzhi Shen³, Ruobai Li², Cuiwen Tan², Tiansheng Chen², Haijin Liu⁴, Yang Liu⁵, Zongwei Cai⁶, Guoguang Liu⁷, Wenying Lv⁸

Affiliations

¹ School of Environmental Science and Engineering, Guangdong University of Technology, Guangzhou, 510006, China; School of Environment, Tsinghua University, Beijing, 100084, China.
² School of Environmental Science and Engineering, Guangdong University of Technology, Guangzhou, 510006, China.
³ School of Environment, Tsinghua University, Beijing, 100084, China.
⁴ School of Environment, Henan Normal University, Key Laboratory for Yellow River and Huaihe River Water Environment and Pollution Control, Xinxiang, 453007, China.
⁵ Faculty of Environmental and Biological Engineering, Guangdong University of Petrochemical Technology, Maoming, 525000, China.
⁶ School of Environmental Science and Engineering, Guangdong University of Technology, Guangzhou, 510006, China; State Key Laboratory of Environmental and Biological Analysis, Department of Chemistry, Hong Kong Baptist University, Hong Kong, China.
⁷ School of Environmental Science and Engineering, Guangdong University of Technology, Guangzhou, 510006, China. Electronic address: liugg615@163.com.
⁸ School of Environmental Science and Engineering, Guangdong University of Technology, Guangzhou, 510006, China. Electronic address: lvwy612@163.com.

PMID: 30384303
DOI: 10.1016/j.chemosphere.2018.10.096

Abstract

In recent years, how to effectively remove emerging organic pollutants in water bodies has been studied extensively, especially in the actual complex water environment. In the present study, an effective wastewater treatment system that combined photocatalysis and an oxidizing agent was investigated. Specifically, visible-light driven reduced graphene oxide (RGO)/TiO₂ composites were prepared, and peroxodisulfate (PDS) was used as electron acceptor to accelerate the photocatalytic activity of this material. The vis-RGO/TiO₂/PDS system exhibited outstanding properties in the degradation of diclofenac (DCF), which was also facilitated by acidic conditions and Cl^-. Lake water, tap water, river water and HCO₃^- decreased the DCF degradation rate, while NO₃^- affected the system only slightly. Low concentrations of fulvic acid (FA) promoted the degradation of DCF via the generation of excited states, whereas a high concentration of FA inhibited the degradation, which was likely due to the light screening effect. The photocatalytic mechanism revealed that PDS served as an electron acceptor for the promotion of electron-hole pair separation and the generation of additional reactive oxygen species, while the RGO served as an electric conductor. The active substances, h⁺, OH, ¹O₂, SO₄^- and O₂^- were generated in this system, O₂^- and h⁺ played significant roles in the degradation of DCF based electron spin resonance tests and radical quenching results. According to the mass spectrometry results, the amide bond cleavage, dechlorination reaction, hydroxyl addition reaction, and decarboxylation reaction were the primary transformative pathways.

Keywords: Environmental factors; Mechanism; Peroxodisulfate; Photocatalysis.

MeSH terms

Catalysis
Graphite / chemistry*
Kinetics
Titanium / chemistry*
Water Pollutants, Chemical / analysis
Water Pollutants, Chemical / chemistry*
Water Purification / methods*

Substances

Water Pollutants, Chemical
titanium dioxide
Graphite
Titanium