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目前,有研究[1]表明,已经有超过5 000种药物在使用后被释放到环境中,其中由于抗生素类药物及其代谢物在低浓度下仍具有一定的生物活性,未经代谢就被排出体外,长期残留在环境中会促使抗生素耐药菌和抗生素耐药基因的形成,对人体健康和生态环境有潜在影响[2-4]。许多研究[5-7]已经证实在地表水、地下水和废水等各类水体中普遍存在抗生素。同时,通过常规污水处理厂去除水中抗生素的处理效果不理想[8-10]。因此,亟需开发出更加绿色经济、稳定高效的抗生素废水处理工艺[11]。目前,电化学高级氧化工艺(electrochemical advanced oxidation process, EAOPs)被认为能够有效去除水中的抗生素[12-15]。在电芬顿(electro-Fenton, EF)体系中,气体扩散电极(gas diffusion electrode, GDE)的气-液-固三相界面结构可以促使空气迅速与溶液接触并发生还原反应,驱动体系实现H2O2的高效产生[16]。ZHANG等[17]用生物质衍生碳对GDE电极进行改性,表现出优秀的H2O2生产能力,电流效率在30 min内可达到95%。但GDE电极还原Fe3+能力较差,因此基于GDE阴极的EF体系的催化效率取决于Fe3+/Fe2+间还原循环速率[18-21]。
基于此,本研究提出通过引入柱状铁棒作为缓释铁源,优化铁离子投加方式,构建了缓释铁源EF体系(slow-release iron source, SRIS-EF),以实现高效同步生成芬顿反应所需Fe2+和H2O2,从而提高体系氧化能力。本研究系统考察了100 mg·L−1 CIP在电化学生成H2O2(electrochemical oxidation-H2O2, EO-H2O2)、EF和SRIS-EF 3种体系中的降解效能,对比了柱状铁棒面积、电流密度和初始pH对SRIS-EF体系降解效能的影响,解析了体系中H2O2、Fe2+和·OH的变化,结合液相色谱及离子色谱等手段,探讨了缓释铁源强化GDE电极的SRIS-EF体系催化降解环丙沙星(ciprofloxacin, CIP)的反应机理。
缓释铁源耦合气体扩散电极强化电芬顿降解环丙沙星
Enhanced degradation of the antibiotic ciprofloxacin by electro-Fenton using a sustained-release iron source coupled with a gas diffusion cathode
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摘要: 气体扩散电极(GDE)气液固三相界面可高效产生H2O2,但对铁离子还原能力较弱。针对这一问题,本文构建了一种基于缓释铁源的电芬顿体系(SRIS-EF),通过引入柱状铁棒与GDE电极协同作用加强体系的氧化能力。该体系旨在改进Fe2+投加方式,通过电场与溶液酸碱度协同作用持续生成Fe2+,提高羟基自由基(·OH)的生成和利用率,加速污染物的降解与矿化。以100 mg·L−1环丙沙星(CIP)为目标物,通过定量分析体系内生成的主要活性氧化物质(ROS)表征其氧化能力,结果表明SRIS-EF能够持续生成更高浓度的·OH。对比了不同体系对CIP的矿化能力,发现SRIS-EF的TOC矿化率与常规EF相比提高了12.1%。此外,考察了SRIS-EF体系中柱状铁棒面积、初始pH、电流密度等因素对降解效能的影响,得出了SRIS-EF体系的最佳条件为:铁棒面积2.89 cm2,初始pH 3.00,电流密度30 mA·cm−2,在此条件下反应60 min即可被完全去除CIP,处理360 min后TOC去除率可达47.3%。还对体系中无机离子和小分子有机酸的生成情况进行了测定,检测出CIP内的N和F主要以NH4+、NO3−和F−形式释放,降解过程中生成了草酸、甲酸、富马酸和丙二酸等四种短链羧酸,其中甲酸浓度较高。研究证实了SRIS-EF体系在降解水中难降解有机污染物方面优异的氧化性能。Abstract: The electro-Fenton (EF) using the gas diffusion electrode (GDE) can produce H2O2 efficiently at the gas-liquid-solid three-phase interface, but its reduction ability for Fe3+ is very weak. A novel EF process of SRIS-EF based on slow-release iron source (SRIS) was constructed, in which the oxidation capacity was enhanced by the synergistic effect of the columnar iron rod and GDE electrode. In SRIS-EF, SRIS can continuously generate Fe2+ by the coeffect of the electric field and the acidity of solution, the generation and utilization of hydroxyl radicals (·OH) are enhanced, the degradation and mineralization of pollutants were accelerated accordingly. The oxidative capacity was characterized by quantifying the major reactive oxygen species (ROS) generated during treating 100 mg·L−1 ciprofloxacin (CIP). The results showed that SRIS-EF could consistently generate more ·OH than EF alone. The mineralization ability of different processes was also compared, the TOC removal rate of SRIS-EF process was 12.1% higher than that of the conventional EF process. In addition, the effects of iron rod area, initial pH and current density of SRIS-EF were studied. The optimal conditions were determined as follows: the area of iron rod was 2.89 cm2, the initial pH was 3.00, and the current density was 30 mA·cm−2. Under the optimal condition, CIP was completely degraded within 60 min, and 47.3% TOC was removed after 360 min treatment. The generations of inorganic ions and organic acids in different processes were measured. The N and F atoms of CIP were mainly released as NH4+, NO3− and F−. Four short-chain carboxylic acids: oxalic acid, formic acid, fumaric acid and malonic acid were detected, the higher concentration of formic acid was generated in SRIS-EF process. The study verified the excellent oxidation performance of SRIS-EF process on the degradation of refractory organic pollutants in water.
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表 1 在不同体系中降解过程的一级动力学表观速率常数及电流矿化效率
Table 1. Apparent pseudo first-order rate constants and mineralization current efficiency in different systems
降解体系 k1/min−1 R2 MCE/% EO-H2O2 0.003 0.989 0.03 EF 0.379 0.963 2.53 SRIS-EF 0.144 0.968 6.57 表 2 不同柱状铁棒面积下反应体系中Fe2+浓度、H2O2浓度和TOC去除率的变化
Table 2. Evolution of Fe2+, H2O2 and TOC removal rates in SRIS-EF with different columnar iron rod areas
铁钉面积/
cm2Fe2+浓度/
(mg·L−1)H2O2累积浓度/
(mmol·L−1)TOC
去除率/%0 — 41.55 6.1 1.45 16.42 17.79 38.7 2.17 25.34 14.31 44.1 2.89 32.59 12.26 47.3 3.25 36.70 7.78 44.3 -
[1] DORIVAL‐GARCíA N, ZAFRA‐GóMEZ A, CANTARERO S, et al. Simultaneous determination of 13 quinolone antibiotic derivatives in wastewater samples using solid‐phase extraction and ultra performance liquid chromatography–tandem mass spectrometry[J]. Microchemical Journal, 2013, 106: 323-333. doi: 10.1016/j.microc.2012.09.002 [2] VAN DOORSLAER X, DEWULF J, VAN LANGENHOVE H, et al. Fluoroquinolone antibiotics: an emerging class of environmental micropollutants[J]. Science of the Total Environment, 2014, 500: 250-269. [3] DORIVAL-GARCIA N, ZAFRA-GOMEZ A, NAVALON A, et al. Removal and degradation characteristics of quinolone antibiotics in laboratory-scale activated sludge reactors under aerobic, nitrifying and anoxic conditions[J]. Journal of Environment Management, 2013, 120: 75-83. [4] LI W, SHI Y, GAO L, et al. Occurrence and removal of antibiotics in a municipal wastewater reclamation plant in Beijing, China[J]. Chemosphere, 2013, 92(4): 435-444. doi: 10.1016/j.chemosphere.2013.01.040 [5] CAO S S, DUAN Y P, TU Y J, et al. Pharmaceuticals and personal care products in a drinking water resource of Yangtze River Delta Ecology and Greenery Integration Development Demonstration Zone in China: Occurrence and human health risk assessment[J]. Science of the Total Environment, 2020, 721: 137624. doi: 10.1016/j.scitotenv.2020.137624 [6] BLAIR B D, CRAGO J P, HEDMAN C J, et al. Evaluation of a model for the removal of pharmaceuticals, personal care products, and hormones from wastewater[J]. Science of the Total Environment, 2013, 444: 515-521. doi: 10.1016/j.scitotenv.2012.11.103 [7] KOSMA C I, LAMBROPOULOU D A, ALBANIS T A. Comprehensive study of the antidiabetic drug metformin and its transformation product guanylurea in Greek wastewaters[J]. Water Research, 2015, 70: 436-448. doi: 10.1016/j.watres.2014.12.010 [8] ENIOLA J O, KUMAR R, BARAKAT M A, et al. A review on conventional and advanced hybrid technologies for pharmaceutical wastewater treatment[J]. Journal of Cleaner Production, 2022, 356: 131826. doi: 10.1016/j.jclepro.2022.131826 [9] MACKUĽAK T, ČERNANSKý S, FEHéR M, et al. Pharmaceuticals, drugs, and resistant microorganisms - environmental impact on population health[J]. Current Opinion in Environmental Science & Health, 2019, 9: 40-48. [10] 徐维海, 张干, 邹世春, 等. 典型抗生素类药物在城市污水处理厂中的含量水平及其行为特征[J]. 环境科学, 2007, 28(8): 1779-1783. doi: 10.3321/j.issn:0250-3301.2007.08.023 [11] CAI Y, SUN T, LI G, et al. Traditional and emerging water disinfection technologies challenging the control of antibiotic-resistant bacteria and antibiotic resistance genes[J]. ACS ES& T Engineering, 2021, 1(7): 1046-1064. [12] KLAVARIOTI M, MANTZAVINOS D, KASSINOS D. Removal of residual pharmaceuticals from aqueous systems by advanced oxidation processes[J]. Environment International, 2009, 35(2): 402-417. doi: 10.1016/j.envint.2008.07.009 [13] MONDAL S K, SAHA A K, SINHA A. Removal of ciprofloxacin using modified advanced oxidation processes: Kinetics, pathways and process optimization[J]. Journal of Cleaner Production, 2018, 171: 1203-1214. doi: 10.1016/j.jclepro.2017.10.091 [14] BRILLAS E, SIRéS I. Electrochemical removal of pharmaceuticals from water streams: Reactivity elucidation by mass spectrometry[J]. TRAC Trends in Analytical Chemistry, 2015, 70: 112-121. doi: 10.1016/j.trac.2015.01.013 [15] TOPOLOVEC B, ŠKORO N, PUАČ N, et al. Pathways of organic micropollutants degradation in atmospheric pressure plasma processing: A review[J]. Chemosphere, 2022, 294: 133606. doi: 10.1016/j.chemosphere.2022.133606 [16] BRILLAS E, SIRéS I, OTURAN M A. Electro-Fenton process and related electrochemical technologies based on fenton’s reaction chemistry[J]. Chemical Reviews, 2009, 109(12): 6570-6631. doi: 10.1021/cr900136g [17] ZHANG Y, DANIEL G, LANZALACO S, et al. H2O2 production at gas-diffusion cathodes made from agarose-derived carbons with different textural properties for acebutolol degradation in chloride media[J]. Journal of Hazardous materials, 2022, 423: 127005. doi: 10.1016/j.jhazmat.2021.127005 [18] SIRéS I, OTURAN N, OTURAN M A, et al. Electro-Fenton degradation of antimicrobials triclosan and triclocarban[J]. Electrochimica Acta, 2007, 52(17): 5493-5503. doi: 10.1016/j.electacta.2007.03.011 [19] ISARAIN-CHáVEZ E, ARIAS C, CABOT P L, et al. Mineralization of the drug β-blocker atenolol by electro-Fenton and photoelectro-Fenton using an air-diffusion cathode for H2O2 electrogeneration combined with a carbon-felt cathode for Fe2+ regeneration[J]. Applied Catalysis B:Environmental, 2010, 96(3-4): 361-369. doi: 10.1016/j.apcatb.2010.02.033 [20] SIRéS I, GARRIDO J A, RODRíGUEZ R M, et al. Catalytic behavior of the Fe3+/Fe2+ system in the electro-Fenton degradation of the antimicrobial chlorophene[J]. Applied Catalysis B:Environmental, 2007, 72(3-4): 382-394. doi: 10.1016/j.apcatb.2006.11.016 [21] YANG Z, SHAN C, PAN B, et al. The Fenton reaction in water assisted by picolinic acid: accelerated iron cycling and co-generation of a selective Fe-based oxidant[J]. Environmental Science and Technology, 2021, 55(12): 8299-8308. doi: 10.1021/acs.est.1c00230 [22] 中国国家环境保护总局. 水和废水监测分析方法(第四版)[J]. 北京:中国环境科学出版社, 2002: 368-370. [23] WELCHER F J. Standard methods of chemical analysis[M]. New York Krieger Publishing Company, 1975. [24] YU F, ZHOU M, YU X. Cost-effective electro-Fenton using modified graphite felt that dramatically enhanced on H2O2 electro-generation without external aeration[J]. Electrochimica Acta, 2015, 163: 182-189. doi: 10.1016/j.electacta.2015.02.166 [25] TAI C, PENG J F, LIU J F, et al. Determination of hydroxyl radicals in advanced oxidation processes with dimethyl sulfoxide trapping and liquid chromatography[J]. Analytica Chimica Acta, 2004, 527(1): 73-80. doi: 10.1016/j.aca.2004.08.019 [26] ABOU DALLE A, DOMERGUE L, FOURCADE F, et al. Efficiency of DMSO as hydroxyl radical probe in an electrochemical advanced oxidation process: reactive oxygen species monitoring and impact of the current density[J]. Electrochimica Acta, 2017, 246: 1-8. doi: 10.1016/j.electacta.2017.06.024 [27] HORN D B, SQUIRE C R. The estimation of ammonia using the indophenol blue reaction[J]. Clinica Chimica Acta, 1966, 14(2): 185-194. doi: 10.1016/0009-8981(66)90085-4 [28] WANG A, LI Y-Y, RU J. The mechanism and application of the electro-Fenton process for azo dye Acid Red 14 degradation using an activated carbon fibre felt cathode[J]. Journal of Chemical Technology & Biotechnology, 2010, 85(11): 1463-1470. [29] SKOUMAL M, RODRíGUEZ R M, CABOT P L, et al. Electro-Fenton, UVA photoelectro-Fenton and solar photoelectro-Fenton degradation of the drug ibuprofen in acid aqueous medium using platinum and boron-doped diamond anodes[J]. Electrochimica Acta, 2009, 54(7): 2077-2085. doi: 10.1016/j.electacta.2008.07.014 [30] 王爱民, 曲久辉, 史红星, 等. 活性碳纤维阴极电芬顿反应降解微囊藻毒素研究[J]. 高等学校化学学报, 2005, 26(9): 1669-1672. doi: 10.3321/j.issn:0251-0790.2005.09.013 [31] WEN Z, WANG A, ZHANG Y, et al. Mineralization of cefoperazone in acid medium by the microwave discharge electrodeless lamp irradiated photoelectro-Fenton using a RuO2/Ti or boron-doped diamond anode[J]. Journal of Hazardous materials, 2019, 374: 186-194. doi: 10.1016/j.jhazmat.2019.03.124 [32] RADWAN M, GAR ALALM M, ELETRIBY H. Optimization and modeling of electro-Fenton process for treatment of phenolic wastewater using nickel and sacrificial stainless steel anodes[J]. Journal of Water Process Engineering, 2018, 22: 155-162. doi: 10.1016/j.jwpe.2018.02.003 [33] 高迎新, 张昱, 杨敏, 等. Fe3+或Fe2+均相催化H2O2生成羟基自由基的规律[J]. 环境科学, 2006, 27(2): 305-309. doi: 10.3321/j.issn:0250-3301.2006.02.021 [34] 龚月湘, 兰华春, 李久义, 等. 光电芬顿矿化草甘膦有机废水[J]. 环境工程学报, 2016, 10(8): 3999-4003. doi: 10.12030/j.cjee.201503080 [35] SOPAJ F, OTURAN N, PINSON J, et al. Effect of the anode materials on the efficiency of the electro-Fenton process for the mineralization of the antibiotic sulfamethazine[J]. Applied Catalysis B:Environmental, 2016, 199: 331-341. doi: 10.1016/j.apcatb.2016.06.035 [36] ANTONIN V S, SANTOS M C, GARCIA-SEGURA S, et al. Electrochemical incineration of the antibiotic ciprofloxacin in sulfate medium and synthetic urine matrix[J]. Water Research, 2015, 83: 31-41. doi: 10.1016/j.watres.2015.05.066 [37] 李张丽, 杨健, 贾漫珂, 等. 非水溶性铁Schiff碱配合物活化H2O2光催化降解环丙沙星[J]. 武汉大学学报(理学版), 2021, 67(4): 367-374.