Decolorization of azo dye C.I. Reactive Black 5 by ozonation in aqueous solution: influencing factors, degradation products, reaction pathway and toxicity assessment

2015 ◽  
Vol 73 (7) ◽  
pp. 1500-1510 ◽  
Author(s):  
Qing Zheng ◽  
Yong Dai ◽  
Xiangyun Han

In this study, ozonation treatment of C.I. Reactive Black 5 (RB5) was investigated at various operating parameters. The results showed that the aqueous solution initially containing 200 mg/L RB5 was quickly decolorized at pH 8.0 with an ozone dose of 3.2 g/h. Reaction intermediates with m/z 281, 546, 201, 350, 286 and 222 were elucidated using liquid chromatography-mass spectrometry, while sulfate ion, nitrate ion and three carboxylic acids (i.e., oxalic acid, formic acid, and acetic acid) were identified by ion exchange chromatography. Thus, the cleavage of the azo bond and the introduction of OH groups in the corresponding positions were proposed as the predominant reaction pathway. The detachment of sulfonic groups was also commonly observed during the ozonation treatment. The proposed degradation mechanism was confirmed by frontier electron density calculations, suggesting the feasibility of predicting the major events in the whole ozonation process with the computational method. Compared with RB5 degradation, the reduction of total organic carbon (TOC) proceeded much more slowly, and approximately 54% TOC was removed after 4 h of ozonation. Acute toxicity tests with Photobacterium phosphoreum showed that the toxicity of reaction solution was firstly increased and then decreased to a negligible level after 160 min.

Water ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 3150
Author(s):  
Jianye Xu ◽  
Siqi Zhou ◽  
Erdeng Du ◽  
Yongjun Sha ◽  
Lu Zheng ◽  
...  

The UV/chlorine process, as a new type of AOP (Advanced Oxidation Process), was utilized to treat amlodipine (AML)-containing water. The influencing factors, including chlorine dose, UV intensity, solution initial pH value, and ammonia concentration, were investigated. The degradation of AML in real water and the relative contributions of OH• and Cl• were also studied. Finally, high-resolution mass spectrometry (HRMS) and GC-MS were used to identify the possible degradation products. The results demonstrated that the AML degradation process was fitted with apparent first-order kinetics. AML degradation had a positive correlation with UV intensity and chlorine dose, and a negative correlation with ammonia concentration. In the presence of ammonia nitrogen and DOM, the removal of AML from real water was reduced. OH• made a dominant percentage contribution of 55.7% to the degradation of AML. Sixteen intermediates were detected and identified. A possible degradation mechanism was also proposed. Acute toxicity tests and risk prediction both illustrated that the complete removal of AML does not guarantee the reduction of acute toxicity, but a prolonged degradation promoted the detoxification of toxic intermediates. The UV/chlorine process can be regarded to be an effective method to remove AML and reduce ecological risk.


2012 ◽  
Vol 610-613 ◽  
pp. 1616-1619
Author(s):  
Shu Fang Mei ◽  
Ya Nan Liu

Degradation of Reactive Black 5 in aqueous solution was studied by double-dielectric barrier discharge, degradation efficiency and degradation mechanism has been investigated. Results shows that during in ten minutes degradation, decolorization efficiency can reach 98.76%,COD and TOC could not be reduce observably, while the biodegradability has been greatly improved, the BOD5/COD ratio increase from 0.079 to 0.495.Decolorization efficiency is higher than that of mineralization, decolorization follows the first order kinetics with a constant rate of 0.4008 min-1. pH of the solution decrease gradually, but the conductivity increase during the degradation process. The ions of sulfate, nitrate, acetic acid, and oxalic acid have been found in the final treated sample and their concentrations increase with the reaction time. Chromophore group is damaged firstly and the solution has been decolorized efficiently, the degradation of benzene ring and naphthalene ring is more difficult than that of the azo bond, and the reduction or disappearance of absorption peaks indicates that the aromatic ring of KN-B was degraded partly.


2017 ◽  
Vol 75 (12) ◽  
pp. 2935-2951 ◽  
Author(s):  
Mingguo Peng ◽  
Huajie Li ◽  
Xu Kang ◽  
Erdeng Du ◽  
Dongdong Li

The removal of ibuprofen (IBP) in aqueous solution using UV/H2O2 process was evaluated. The response surface methodology (RSM) and Box–Behnken design were employed to investigate the effects of process parameters on IBP removal, including the initial IBP concentration, H2O2 dosage, UV light intensity, and initial pH value of solution. The RSM model developed herein fits well with the experiments, and provides a good insight into the OH radical irritated degradation mechanisms and kinetics. High resolution accurate mass spectrometry coupled with liquid chromatography was used to identify the degradation intermediates. A total of 23 degradation products were identified, including mono-hydroxylated products and dihydroxylated products. A series of OH radical-initiated reactions, including hydroxylation, dihydroxylation, decarboxylation, demethylation, ring break, lead to the final mineralization of IBP to CO2 and H2O. UV/H2O2 technology could be a promising technology for IBP removal in aqueous solution.


2013 ◽  
Vol 67 (8) ◽  
pp. 1880-1885 ◽  
Author(s):  
Xiaoyan Guo ◽  
Yaping Cai ◽  
Zhongbo Wei ◽  
Haifeng Hou ◽  
Xi Yang ◽  
...  

Interior microelectrolysis (IM) as a pretreatment process was effective to treat Reactive Black 5 (RB5) in this study. The removal rates of chemical oxygen demand (COD), total organic carbon (TOC) and color were 46.05, 39.99 and 98.77%, respectively, when this process was conducted under the following optimal conditions: the volumetric ratio between iron scraps and active carbon (AC) (V(Fe)/V(C)) 1.0, pH 2.0, aeration dosage 0.6 L/min, and reaction time 100 min. Contaminants could be further removed by ozonation. After subsequent ozonation for 200 min, the solution could be completely decolorized, and the COD and TOC removal rates were up to 77.78 and 66.51%, respectively. In addition, acute toxicity tests with Daphnia magna showed that pretreatment by IM generated effluents that were more toxic when compared with the initial wastewater, and the toxicity was reduced after subsequent ozonation.


Molecules ◽  
2021 ◽  
Vol 26 (4) ◽  
pp. 1059
Author(s):  
Jin Young Lee ◽  
Kyoung Chan Lim ◽  
Hyun Suk Kim

As a first step toward studying the properties of Novichok (ethyl (1-(diethylamino)ethylidene)phosphoramidofluoridate (A234)), we investigated its degradation products and fragmentation pathways in aqueous solution at different pH levels by liquid chromatography–tandem mass spectrometry. A234 was synthesized in our laboratory and characterized by nuclear magnetic resonance spectroscopy. Three sets of aqueous samples were prepared at different pH levels. A stock solution of A234 was prepared in acetonitrile at a concentration of 1 mg/mL and stored at −20 °C until use. Aqueous samples (0.1 mg/mL) were prepared by diluting the stock solution with deionized water. The acidic aqueous sample (pH = 3.5) and basic aqueous sample (pH = 9.4) were prepared using 0.01 M acetic acid and 0.01 M potassium carbonate, respectively. The analysis of the fragmentation patterns and degradation pathways of A234 showed that the same degradation products were formed at all pH levels. However, the hydrolysis rate of A234 was fastest under acidic conditions. In all three conditions, the fragmentation pattern and the major degradation product of A234 were determined. This information will be applicable to studies regarding the decontamination of Novichok and the trace analysis of its degradation products in various environmental matrices.


2010 ◽  
Vol 174 (1-3) ◽  
pp. 795-800 ◽  
Author(s):  
Hua-Wei Chen ◽  
Yu-Lin Kuo ◽  
Chyow-San Chiou ◽  
Shih-Wei You ◽  
Chih-Ming Ma ◽  
...  

Author(s):  
Ahmed E. Al Prol Khalid M. El Moselhy ◽  
Magdi Abdel Azzem kamel Adel Amer ◽  
Mahmoud Abdel Moneim

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