| 摘要: |
| 以有机染料罗丹明B为目标污染物，利用光电芬顿方法对其进行降解研究。研究汇总考察了芬顿试剂（二价铁盐、双氧水）的用量及比例、初始pH值、电流强度等对罗丹明B降解效果的影响。实验结果表明：芬顿试剂H2O2 / Fe2+的最佳物质的量比为1∶1，Fe2+浓度降低或H2O2浓度升高，罗丹明B降解效果增强；罗丹明B在pH＝3.0的酸性体系中降解效果最好；电流强度为0.005 A时，罗丹明B降解效果好且耗能最低。在H2O2 / Fe2+物质的量比为1∶1、电流为0.005 A、初始pH＝3.0、H2O2初始浓度为1.0 mM条件下，以350 nm紫外光照射的光电芬顿反应降解初始浓度为0.1 mM的罗丹明B溶液，处理10 min后罗丹明B去除效率可达99%以上。 |
| 关键词: 光电芬顿 罗丹明B 影响参数 降解效果 |
| DOI：10.7515/JEE201706010 |
| 分类号: |
| 基金项目:国家自然科学基金项目（41503102）；中国博士后基金（2015M572568）；陕西省博士后基金（2016BSHEDZZ35）；
香港理工大学基金（G-YBHP） |
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| Dye Rhodamine B degradation by photo-Electric Fenton’s oxidation |
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CHEN Meijuan1，2, CHU Wei2, WONG Yuktung2
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1. School of Human Settlements and Civil Engineering, Xi’an Jiaotong University, Xi’an 710049, China
2. Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China
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| Abstract: |
| Background, aim, and scope The synthetic dyes is undesirable in water because the coloring agents are harmful to the aquatic environment. Rhodamine B (RhB) is an important representative of xanthene-based dyes. Human exposure to RhB can cause irritation in contact with skin, eyes and respiratory tract. Fenton reaction is proven to be an efficient oxidation process for organic pollutants in previous literatures, due to the fact that ferrous salt is widely available, non-toxic and relative cheap and that the end product is environmentally benign. The hydroxyl radical (∙OH) is the active species to degrade target compounds in Fenton reaction. However, the rapid depletion and slow regeneration of ferrous ions throughout the reaction is one of the main drawbacks in classical Fenton process (Fe2+ + H2O2 → Fe3+ + OH− + ∙OH). In the photo-Fenton and electro-Fenton process, the catalytic reaction is propagated by Fe(Ⅱ) regeneration to overcome the drawback in classical Fenton process. Materials and methods In this study, a novel electric photo-Fenton process was employed, the Fenton’s reagents of ferrous ions (Fe2+) and H2O2 were used in the electrochemical cell to produce hydroxyl radicals, the iron steel worked as sacrificial anode for the generation of supplementary Fe2+, and Fe2+ were also regenerated via the reduction of ferric ions by the cathode and UV light. The dye RhB was chosen as a target pollutant to evaluate the performance in aqueous solution. Three types of Fenton reactions (i.e. sole-Fenton, photo-Fenton and electro photo-Fenton) were studied and compared. The effect parameters such as pH, hydrogen peroxide concentration, ferrous ion dosage, and electric current were evaluated and optimized. Results Three types of Fenton processes (i.e. sole-Fenton, photo-Fenton and electro photo-Fenton) were conducted to identify the RhB degradation efficiency. The electro photo-Fenton shows best performance to RhB degradation. Meanwhile, in the electro photo-Fenton process, the effect of H2O2/Fe(Ⅱ) molar ratio was examined in the range from 1∶10 (5∶50) to 10∶1, respectively. As the [H2O2]0 fixed at 0.5 mM or 1.0 mM, the decay efficiency were both increased with the decrement of Fe (Ⅱ) and the optimum RhB decay was achieved at H2O2/Fe(Ⅱ) molar ratio＝1∶1. Next, the influence of solution pH on RhB degradation was examined with the pH value in the range from 2.0 to 4.0. The highest RhB degradation efficacy was reached at an initial pH value around 3.0, and the degradation performances of above or below this pH value were worse. Finally, The influence of the electric current (I ) on the RhB degradation was studied in the range from 0.002 A to 0.030 A at current-controlled conditions. A significant jump was observed when I increased from 0.002 A to 0.005 A. However, the decay rate leveled off as the electric current further increased.Discussion (a) The outstanding performance of electro photo-Fenton than other types of Fenton processes was achieved by an extra application of electrochemical method, where Fenton reagents of H2O2 and Fe2+ can both be re-generated. (b) The optimum RhB decay was achieved at H2O2/Fe(Ⅱ) molar ratio =1, after which the decay performance levelled off. On the other hand, the increment of [H2O2H0 always brought the performance improvement, while the decreament of Fe(Ⅱ) dosage improved the decay performance. (c) The increment of decay rate at higher current at the range of 0.002 — 0.005 A was likely attributed to the faster release of H2O2 on the cathode. Conclusions The electric photo-Fenton with a sacrificed anode showed the optimum performance for RhB degradation. The degradation curve can be defined as a two-stage reaction comprised of a rapid first stage and a retarded second stage. The effect of various parameters such as the Fenton reagent H2O2 / Fe(Ⅱ) molar ratio, initial solution pH value, and electric current was further investigated and optimized. The optimal conditions were H2O2∶Fe(Ⅱ) molar ratio = 1∶1, pH = 3.0, and electric current = 0.005A. The experimental results showed that the RhB degradation efficiency under the optimal parameters condition can achieve more than 99% in 10 min. Recommendations and perspectives The photo-Electric Fenton’s oxidation technology is a promising technology to removal synthetic dyes, and the generation of less ferric hydroxide sludge would reduce the workload for additional separation and disposal. It can be combined with other technologies to give full play to its advantages. |
| Key words: electric photo-Fenton Rhodamine B effect parameters degradation efficiency |
