Unusual Catalytic Effect of Fe<sup>3+</sup> on 2,4-dichlorophenoxyacetic Acid Degradation by Radio Frequency Discharge in Aqueous Solution
2,4-dichlorophenoxyacetic acid (2,4-D) is a widely used herbicide for controlling broad-leaved weeds. The development of an efficient process for treating the refractory 2,4-D wastewater is necessary. In this study, liquid-phase degradation of 2,4-D induced by radio frequency discharge (RFD) was stu...
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MDPI AG
2022-05-01
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| author | Yongjun Liu Bing Sun |
| author_facet | Yongjun Liu Bing Sun |
| author_sort | Yongjun Liu |
| collection | DOAJ |
| description | 2,4-dichlorophenoxyacetic acid (2,4-D) is a widely used herbicide for controlling broad-leaved weeds. The development of an efficient process for treating the refractory 2,4-D wastewater is necessary. In this study, liquid-phase degradation of 2,4-D induced by radio frequency discharge (RFD) was studied. Experimental results showed that the degradation was more effective in acidic than in neutral or alkaline solutions. During the degradation, a large amount of hydrogen peroxide (H<sub>2</sub>O<sub>2,</sub> 1.2 mM/min, almost equal to that without 2,4-D) was simultaneously produced, and catalytic effects of both ferric (Fe<sup>3+</sup>) and ferrous (Fe<sup>2+</sup>) ions on the degradation were examined and compared. It was found that 2,4-D degraded more rapidly in the case of Fe<sup>3+</sup> than the that of Fe<sup>2+</sup>. Such a scenario is explained that Fe<sup>3+</sup> was successively reduced to Fe<sup>2+</sup> by the atomic hydrogen (•H) and •OH-adducts of 2,4-D resulting from RFD, which in turn catalyzed the H<sub>2</sub>O<sub>2</sub> to form more •OH radicals through Fenton’s reaction, indicating that Fe<sup>3+</sup> not only accelerates the degradation rate but also increases the amount of •OH available for 2,4-D degradation by suppressing the back reaction between the •H and •OH. 2,4-dichlorophenol, 4,6-dichlororesorcinol, 2-hydroxy-4-chloro- and 2-chloro-4-hydroxy- phenoxyacetic acids, hydroxylated 2,4-Ds, and carboxylic acids (glycolic, formic and oxalic) were identified as the byproducts. Energy yields of RFD have been compared with those of other nonthermal plasma processes. |
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| spelling | doaj.art-57b7cfcf756e44af9bf5f0d93785cd612023-11-23T15:01:42ZengMDPI AGWater2073-44412022-05-011411171910.3390/w14111719Unusual Catalytic Effect of Fe<sup>3+</sup> on 2,4-dichlorophenoxyacetic Acid Degradation by Radio Frequency Discharge in Aqueous SolutionYongjun Liu0Bing Sun1College of Environmental Science & Engineering, Dalian Maritime University, Dalian 116026, ChinaCollege of Environmental Science & Engineering, Dalian Maritime University, Dalian 116026, China2,4-dichlorophenoxyacetic acid (2,4-D) is a widely used herbicide for controlling broad-leaved weeds. The development of an efficient process for treating the refractory 2,4-D wastewater is necessary. In this study, liquid-phase degradation of 2,4-D induced by radio frequency discharge (RFD) was studied. Experimental results showed that the degradation was more effective in acidic than in neutral or alkaline solutions. During the degradation, a large amount of hydrogen peroxide (H<sub>2</sub>O<sub>2,</sub> 1.2 mM/min, almost equal to that without 2,4-D) was simultaneously produced, and catalytic effects of both ferric (Fe<sup>3+</sup>) and ferrous (Fe<sup>2+</sup>) ions on the degradation were examined and compared. It was found that 2,4-D degraded more rapidly in the case of Fe<sup>3+</sup> than the that of Fe<sup>2+</sup>. Such a scenario is explained that Fe<sup>3+</sup> was successively reduced to Fe<sup>2+</sup> by the atomic hydrogen (•H) and •OH-adducts of 2,4-D resulting from RFD, which in turn catalyzed the H<sub>2</sub>O<sub>2</sub> to form more •OH radicals through Fenton’s reaction, indicating that Fe<sup>3+</sup> not only accelerates the degradation rate but also increases the amount of •OH available for 2,4-D degradation by suppressing the back reaction between the •H and •OH. 2,4-dichlorophenol, 4,6-dichlororesorcinol, 2-hydroxy-4-chloro- and 2-chloro-4-hydroxy- phenoxyacetic acids, hydroxylated 2,4-Ds, and carboxylic acids (glycolic, formic and oxalic) were identified as the byproducts. Energy yields of RFD have been compared with those of other nonthermal plasma processes.https://www.mdpi.com/2073-4441/14/11/1719aqueous solutionradio frequency discharge2,4-DdegradationFenton |
| spellingShingle | Yongjun Liu Bing Sun Unusual Catalytic Effect of Fe<sup>3+</sup> on 2,4-dichlorophenoxyacetic Acid Degradation by Radio Frequency Discharge in Aqueous Solution Water aqueous solution radio frequency discharge 2,4-D degradation Fenton |
| title | Unusual Catalytic Effect of Fe<sup>3+</sup> on 2,4-dichlorophenoxyacetic Acid Degradation by Radio Frequency Discharge in Aqueous Solution |
| title_full | Unusual Catalytic Effect of Fe<sup>3+</sup> on 2,4-dichlorophenoxyacetic Acid Degradation by Radio Frequency Discharge in Aqueous Solution |
| title_fullStr | Unusual Catalytic Effect of Fe<sup>3+</sup> on 2,4-dichlorophenoxyacetic Acid Degradation by Radio Frequency Discharge in Aqueous Solution |
| title_full_unstemmed | Unusual Catalytic Effect of Fe<sup>3+</sup> on 2,4-dichlorophenoxyacetic Acid Degradation by Radio Frequency Discharge in Aqueous Solution |
| title_short | Unusual Catalytic Effect of Fe<sup>3+</sup> on 2,4-dichlorophenoxyacetic Acid Degradation by Radio Frequency Discharge in Aqueous Solution |
| title_sort | unusual catalytic effect of fe sup 3 sup on 2 4 dichlorophenoxyacetic acid degradation by radio frequency discharge in aqueous solution |
| topic | aqueous solution radio frequency discharge 2,4-D degradation Fenton |
| url | https://www.mdpi.com/2073-4441/14/11/1719 |
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