Degradation kinetics of target compounds and correlations with spectral indices during UV/H(2)O(2) post-treatment of biologically treated acrylonitrile wastewater.

Affiliation

Tu X(1), Meng X(2), Pan Y(3), Crittenden JC(2), Wang Y(2).
Author information:
(1)State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, 100012, Beijing, PR China.
(2)School of Civil and Environmental Engineering, Georgia Institute of Technology, 30332, Atlanta, GA, United States.
(3)Jiangsu Provincial Key Laboratory of Environmental Science and Engineering, Suzhou University of Science and Technology, 215011, Suzhou, China. Electronic address: [Email]

Abstract

In this study, the post-treatment of biologically treated acrylonitrile wastewater was investigated during UV/H2O2 process. Five contaminants in the effluent were selected as target compounds, including Furmaronitrile (FMN), 3-Pyridinecarbonitrile (3PCN), 1,3-Dicyanobenzene (1,3-DCB), 5-Methyl-1H-benzotriazole (5MBT), and 7-Azaindole (7AID). Under optimal reaction conditions, the UV/H2O2 post-treatment exhibited good performances in destruction of organic compounds and toxicity. The photo-chemical parameters of the target compounds were measured and it was found that 5MBT and 3PCN had fast degradation rate constants under direct UV photolysis. The second-order rate constants of the target compounds with hydroxyl radicals were determined to be in the range of (1.0-5.0) × 109 M-1 s-1 at pH 3.0 and 25 °C. A simplified pseudo-first-order steady state (Sim-PSS) model, which considered direct UV photolysis and radical oxidation simultaneously, agreed well with the experimental data from the post-treatment of a biologically treated effluent. High-performance size exclusion chromatography (HPSEC) coupled with diode-array detector (DAD) and fluorescence detector (FLD) analysis revealed that humic-like sub-peak signals from different molecular weights of fluorescent organic matter decreased consistently during the oxidation process, which made humic-like fluorescence exhibit higher correlation with the target compounds' degradation than the spectral indices of UV absorbance at 254 nm (UVA254) and protein-like fluorescence.