Degradation kinetics and mechanism of 3-Chlorobenzoic acid in anoxic water environment using graphene/TiO₂ as photocatalyst

ABSTRACT

Degradation kinetics and mechanism of 3-Chlorobenzoic acid (3-CBA) in anoxic water environment using graphene/TiO₂ (GR/TiO₂) as photocatalyst had been investigated. The effects of various parameters such as catalyst dosage, pH, initial concentration, catalyst reuse and dissolved oxygen (DO) on 3-CBA photocatalytic degradation kinetics were studied. The qualitative and quantitative analysis for degradation intermediate products and parent compound were studied by using HPLC, HPLC/MS/MS and IC technologies. The results show that the residual concentration of 3-CBA has a good linear relationship and its correlation coefficient R² are all greater than 0.985 by Langmuir–Hinshelwood (L–H) dynamic model under different photocatalytic degradation conditions. Some oxidative degradation products such as 3-chlorophenol, resorcinol, and hydroxyquinol are generated, and some reductive degradation products such as 3-chlorobenzaldehyde, 3-hydroxybenzaldehyde, 3-hydroxybenzyl alcohol, and cyclohexanediol are produced, and part of 3-CBA are mineralized to generate CO₂ when DO is in the range of 0.5–1.0 mg/L; When DO is less than 0.28 mg/L, photocatalytic reduction mainly occurs. The results provide a theoretical basis for photocatalytic in situ remediation of pollutants in anoxic water environment.

GRAPHICAL ABSTRACT

KEYWORDS:

• GR/TiO₂ 3-Chlorobenzoic acid
• degradation kinetics
• degradation mechanism
• anoxic water environment

Acknowledgements

The authors would like to express our sincere gratitude to the other teachers who gave theoretical and experimental guidance to this article.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

We gratefully acknowledge the financial support of the cultivation fund of the key scientific and technical innovation project, Ministry of Education of China (No. 508057), the Scientific Research foundation of Jiangxi Provincial Department of Education (GJJ10116), the Scientific Research Foundation of Jiangxi provincial (2010BSB03003).