微波无极紫外灯直接光降解去除水中抗生素恩诺沙星机理研究
发布时间：2018-08-10 22:05
【摘要】：微波无极灯光降解技术具备快速、高效、实用性强等优点,已被成功用于去除水相中多种有机污染物。目前该方法研究主要集中在微波无极灯与氧化剂、催化剂联用工艺去除污染物方面,而对微波无极紫外灯直接光降解有机物研究较少。当前抗生素滥用问题严重,抗生素物质已进入各类水体,引起一系列环境问题,危害人类健康,亟需开发出高效的工艺去除水中的抗生素类污染物。本论文提出利用新型紫外光源微波无极灯直接光降解去除水中氟喹诺酮类抗生素恩诺沙星(ENRO),利用光源发射的真空紫外光(185nm)和高强度远紫外光(254nm)对ENRO进行光化学降解,研究从溶解氧(DO)和初始pH两个影响因素入手,系统考察了低浓度(5 mg L-1)和高浓度(50 mg L-1)ENRO在不同微波无极灯光降解(MW/UV)体系中降解效能与反应机理,通过对降解过程中间产物的检测,提出了 ENRO在MW/UV过程中的降解历程。同时研究了 ENRO与Fe(Ⅱ/Ⅲ)的螯合行为及其对MW/UV过程降解ENRO效能影响。研究结果如下:(1)在酸性(pH = 3.0)条件下,MW/UV体系能够高效降解水相中高浓度(50 mg L-1)ENRO。在02,Air和N2氛围下,ENRO光化学降解受DO影响较小,降解过程符合准一级反应动力学方程,其反应速率常数k分别为0.095 min-1(02)、0.075 min-1(Air)和0.083 min-1(N2);而在三种气体氛围条件下DO对MW/UV矿化能力影响很大,在O2,Air和N2氛围下的TOC去除率分别为70.3%,61.7%和46.6%,表明DO参与ENRO的矿化过程。MW/UV体系降解ENRO过程中检测到14种芳环降解中间产物、4种有机酸(草酸、草氨酸、富马酸及甲酸)以及无机产物(F-、NH4+、NO3-),气体氛围对ENRO降解中间产物的生成具有很大影响;在此基础上提出ENRO在MW/UV体系中的三种主要降解途径:(i)氟溶剂化(fluorine solvolysis),(ⅱ)轻基化(hydroxylated)和(iii)乙基哌嗪侧链醛基化(piperazinyl aldehyde)。(2)在中性(pH = 7.0)条件下,MW/UV体系也能够高效降解水相中高浓度(50 mg L-1)ENRO。溶液的DO及初始pH对MW/UV降解水相中ENRO效果有不同影响。在pH = 2.0-10.0区间,ENRO降解速率在pH = 2.0-5.0范围内呈现O2AirN2的规律;而在pH=6.0-10.0范围内呈现N2AirO2的规律,这与ENRO的两性离子态有关。而在pH = 2.0-10.0区间,MW/UV的矿化能力均表现为02AirN2,在中性条件和O2氛围条件下,TOC去除率最高可达到46.5%。MW/UV体系降解ENRO过程中也检测到4种有机酸(草酸、草氨酸、富马酸及甲酸)以及无机产物(F-、NH4+、NO3-),气体氛围对ENRO降解中间产物的生成具有很大影响。对低浓度(5 mg L-1)ENRO的降解研究发现不同气体氛围均能有效降解ENRO,在光解进行5 min后ENRO去除率均达到90%以上。低浓度条件下阴离子(NO3-、SO42-、Cl-、CO32-和HCO3-)对降解有不同影响,浓度为5mg L-1时,除Cr以外其余均对ENRO降解过程有一定的促进作用;浓度为10 mg L-1时,CO32和 HCO3-对ENRO降解过程有所促进,其余阴离子对ENRO的降解过程则表现出抑制作用;浓度为15 mg L-1时,Cl-与CO32-对ENRO降解过程几乎无影响,SO42-和HCO3-表现为促进作用,NO3-表现出一定的抑制作用。(3)气体氛围与初始pH对微波无极灯光降解过程机理影响较大,通过分析各体系生成的H2O2情况发现:溶液DO含量升高,H2O2生成浓度提高,酸性条件也有利于H2O2生成,在02氛围和pH 3.00条件下H2O2生成浓度最高,达到41.3μM;中性条件下O2氛围条件中H2O2生成浓度最高,达到38.3 μM;利用自由基捕获剂手段的方式验证MW/UV反应机理,结果表明在不同DO条件下,MWUV光解纯水过程在加入四种·OH捕获剂后,在N2氛围条件下生成H2O2浓度明显降低,而O2和Air氛围中H2O2含量则呈明显升高。MWUV光降解ENRO过程中加入多种捕获剂后,ENRO降解速率均有所减慢,速率常数由0.095 min-1变为0.057 min-1(叔丁醇 Tert-butanol),0.042 min-1(异丙醇 2-propanol),0.031 min-1(甲醇 Methanol)和0.019 min-1(正丁醇N-butanol),这表明MWUV降解ENRO过程中'OH起到很大作用。(4)ENRO与Fe(Ⅲ)发生螯合作用,螯合会抑制ENRO在MW/UV中光降解。ENRO浓度、Fe(Ⅲ)浓度及溶液pH值均会影响二者的螯合效果,确定最佳螯合比为[ENRO]:[Fe(Ⅲ)]= 1:1。在 0.mM[Fe(Ⅱ/Ⅲ)]条件下(O2,pH=3.0)ENRO溶液的降解速率无分别降低至0.056min-1(R2=0.996)和0.048 min-1(R2=0.990),并且在不同Fe(Ⅱ/Ⅲ)浓度条件下,DO与初始pH对MW/UV体系降解ENRO速率均有所降低,即Fe(Ⅱ/Ⅲ)的存在会抑制ENRO降解;在未外加Fc(Ⅱ/Ⅲ)时,MW/UV(02,pH=3.0)反应120 min后TOC去除率为70.1%,当加入不同浓度的Fe(Ⅱ/Ⅲ)时,反应中溶液的TOC去除率均有所降低,在最佳螯合比浓度时(约0.10 mM)降低最显著,分别达到45.4%(Fe(Ⅱ)和45.8%(Fe(Ⅲ),结果表明Fe(Ⅱ/Ⅲ)的存在会对MW/UV过程中ENRO矿化也起到抑制作用。
[Abstract]:Microwave electrodeless lamp has been successfully used to remove many kinds of organic pollutants in aqueous phase due to its advantages of high speed, high efficiency and high practicability. Nowadays, antibiotic abuse is serious. Antibiotic substances have entered various kinds of water bodies, causing a series of environmental problems and endangering human health. It is urgent to develop efficient processes to remove antibiotic pollutants from water. In this paper, a new type of ultraviolet light source microwave electrodeless lamp is proposed to remove enroxa, a fluoroquinolone antibiotic in water by direct photodegradation. Star (ENRO) was photochemical degraded by vacuum ultraviolet light (185 nm) and high intensity far ultraviolet light (254 nm). The degradation efficiency and anti-degradation of low concentration (5 mg L-1) and high concentration (50 mg L-1) ENRO in different microwave electrodeless lamp degradation (MW/UV) systems were systematically investigated from two factors of dissolved oxygen (DO) and initial pH. The chelating behavior of ENRO with Fe (II/III) and its effect on the degradation efficiency of ENRO in MW/UV process were studied. The results were as follows: (1) MW/UV system could degrade high concentration (50 mg L-3.0) in aqueous phase efficiently under acidic condition. 1) The photochemical degradation of ENRO was less affected by DO in the atmosphere of 02, Air and N2, and the degradation process accorded with the Quasi-First-Order reaction kinetics equation. The reaction rate constants K were 0.095 min-1 (02), 0.075 min-1 (Air) and 0.083 min-1 (N2), respectively. DO had a great influence on the mineralization ability of MW/UV in the atmosphere of O2, Air and N2. The removal rates of DO were 70.3%, 61.7% and 46.6% respectively, indicating that DO was involved in the mineralization of ENRO. Three main degradation pathways of ENRO in MW / UV system were proposed: (i) fluorine solvolysis, (i i) hydroxylated and (i I i) piperazinyl aldehyde. (2) MW / UV system can also degrade DO and initial concentration of ENRO. solution in water phase efficiently under neutral (pH = 7.0). In the range of pH=2.0-10.0, the degradation rate of ENRO showed the regularity of O2 AirN2, while in the range of pH=6.0-10.0, the regularity of N2AirO2 was related to the amphoteric ionic state of ENRO. The removal rate of TOC was up to 46.5% under the condition of parts and O2. Four organic acids (oxalic acid, oxalic acid, fumaric acid and formic acid) and inorganic products (F-, NH4+, NO3-) were also detected during the degradation of ENRO in MW/UV system. Gas atmosphere had a great influence on the formation of intermediate products in ENRO degradation. ENRO can be effectively degraded in the same gas atmosphere, and the removal rate of ENRO can reach above 90% after 5 minutes of photolysis. The anions (NO3-, SO42-, Cl-, CO32-and HCO3-) have different effects on the degradation at low concentration. When the concentration of Cr is 5 mg L-1, the degradation process of ENRO can be promoted by CO32 and HCO3-except Cr. The degradation process of ENRO was promoted by Cl-and CO32-at 15 mg L-1, SO42-and HCO3-at 15 mg L-1, and NO3-at 15 mg L-1. (3) The effect of gas atmosphere and initial pH on the degradation mechanism of ENRO was studied. It was found that the concentration of H2O2 in the solution increased with the increase of DO content and the formation of H2O2, and the formation of H2O2 was facilitated by acidic conditions. The highest concentration of H2O2 was 41.3 mu M under the condition of 02 and pH 3.00, and the highest concentration of H2O2 was 38.3 mu M under the condition of neutral O2. The results show that under different DO conditions, the concentration of H2O2 produced by MWUV photolysis of pure water in N2 atmosphere decreases significantly, while the content of H2O2 in O2 and AIR atmosphere increases significantly. The degradation rate of ENRO is improved by adding various trapping agents in the process of MWUV photolysis of ENRO. The rate constants changed from 0.095 min-1 to 0.057 min-1 (Tert-butanol), 0.042 min-1 (isopropanol 2-propanol), 0.031 min-1 (methanol methanol) and 0.019 min-1 (n-butanol), which indicated that'OH played an important role in the degradation of ENRO by MWUV. (4) ENRO chelated with Fe (III) and the chelation inhibited ENRO photodegradation in MWUV/UV. The concentration of ENRO, the concentration of Fe (III) and the pH value of the solution all affect the chelating effect of the two. The optimum chelating ratio is determined to be [ENRO]: [Fe (III)] = 1:1. Under the condition of 0.mM [Fe (II/III)], (O2, pH = 3.0) the degradation rate of ENRO solution is not reduced to 0.056 min-1 (R2 = 0.996) and 0.048 min-1 (R2 = 0.990) respectively, and DO and 0.048 min-1 (R2 = 0.990) at different concentrations of Fe (II/III). Initial pH decreased ENRO degradation rate of MW/UV system, that is, the presence of Fe (II/III) inhibited ENRO degradation; without Fc (II/III), the removal rate of TOC was 70.1% after 120 minutes of MW/UV (02, pH=3.0). When different concentrations of Fe (II/III) were added, the removal rate of TOC in the reaction solution was reduced, and at the optimum chelation ratio concentration (about 0.10 m). The results showed that the presence of Fe (II/III) also inhibited ENRO mineralization in MW/UV process.
【学位授予单位】：北京交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X703
本文编号：2176346
[Abstract]:Microwave electrodeless lamp has been successfully used to remove many kinds of organic pollutants in aqueous phase due to its advantages of high speed, high efficiency and high practicability. Nowadays, antibiotic abuse is serious. Antibiotic substances have entered various kinds of water bodies, causing a series of environmental problems and endangering human health. It is urgent to develop efficient processes to remove antibiotic pollutants from water. In this paper, a new type of ultraviolet light source microwave electrodeless lamp is proposed to remove enroxa, a fluoroquinolone antibiotic in water by direct photodegradation. Star (ENRO) was photochemical degraded by vacuum ultraviolet light (185 nm) and high intensity far ultraviolet light (254 nm). The degradation efficiency and anti-degradation of low concentration (5 mg L-1) and high concentration (50 mg L-1) ENRO in different microwave electrodeless lamp degradation (MW/UV) systems were systematically investigated from two factors of dissolved oxygen (DO) and initial pH. The chelating behavior of ENRO with Fe (II/III) and its effect on the degradation efficiency of ENRO in MW/UV process were studied. The results were as follows: (1) MW/UV system could degrade high concentration (50 mg L-3.0) in aqueous phase efficiently under acidic condition. 1) The photochemical degradation of ENRO was less affected by DO in the atmosphere of 02, Air and N2, and the degradation process accorded with the Quasi-First-Order reaction kinetics equation. The reaction rate constants K were 0.095 min-1 (02), 0.075 min-1 (Air) and 0.083 min-1 (N2), respectively. DO had a great influence on the mineralization ability of MW/UV in the atmosphere of O2, Air and N2. The removal rates of DO were 70.3%, 61.7% and 46.6% respectively, indicating that DO was involved in the mineralization of ENRO. Three main degradation pathways of ENRO in MW / UV system were proposed: (i) fluorine solvolysis, (i i) hydroxylated and (i I i) piperazinyl aldehyde. (2) MW / UV system can also degrade DO and initial concentration of ENRO. solution in water phase efficiently under neutral (pH = 7.0). In the range of pH=2.0-10.0, the degradation rate of ENRO showed the regularity of O2 AirN2, while in the range of pH=6.0-10.0, the regularity of N2AirO2 was related to the amphoteric ionic state of ENRO. The removal rate of TOC was up to 46.5% under the condition of parts and O2. Four organic acids (oxalic acid, oxalic acid, fumaric acid and formic acid) and inorganic products (F-, NH4+, NO3-) were also detected during the degradation of ENRO in MW/UV system. Gas atmosphere had a great influence on the formation of intermediate products in ENRO degradation. ENRO can be effectively degraded in the same gas atmosphere, and the removal rate of ENRO can reach above 90% after 5 minutes of photolysis. The anions (NO3-, SO42-, Cl-, CO32-and HCO3-) have different effects on the degradation at low concentration. When the concentration of Cr is 5 mg L-1, the degradation process of ENRO can be promoted by CO32 and HCO3-except Cr. The degradation process of ENRO was promoted by Cl-and CO32-at 15 mg L-1, SO42-and HCO3-at 15 mg L-1, and NO3-at 15 mg L-1. (3) The effect of gas atmosphere and initial pH on the degradation mechanism of ENRO was studied. It was found that the concentration of H2O2 in the solution increased with the increase of DO content and the formation of H2O2, and the formation of H2O2 was facilitated by acidic conditions. The highest concentration of H2O2 was 41.3 mu M under the condition of 02 and pH 3.00, and the highest concentration of H2O2 was 38.3 mu M under the condition of neutral O2. The results show that under different DO conditions, the concentration of H2O2 produced by MWUV photolysis of pure water in N2 atmosphere decreases significantly, while the content of H2O2 in O2 and AIR atmosphere increases significantly. The degradation rate of ENRO is improved by adding various trapping agents in the process of MWUV photolysis of ENRO. The rate constants changed from 0.095 min-1 to 0.057 min-1 (Tert-butanol), 0.042 min-1 (isopropanol 2-propanol), 0.031 min-1 (methanol methanol) and 0.019 min-1 (n-butanol), which indicated that'OH played an important role in the degradation of ENRO by MWUV. (4) ENRO chelated with Fe (III) and the chelation inhibited ENRO photodegradation in MWUV/UV. The concentration of ENRO, the concentration of Fe (III) and the pH value of the solution all affect the chelating effect of the two. The optimum chelating ratio is determined to be [ENRO]: [Fe (III)] = 1:1. Under the condition of 0.mM [Fe (II/III)], (O2, pH = 3.0) the degradation rate of ENRO solution is not reduced to 0.056 min-1 (R2 = 0.996) and 0.048 min-1 (R2 = 0.990) respectively, and DO and 0.048 min-1 (R2 = 0.990) at different concentrations of Fe (II/III). Initial pH decreased ENRO degradation rate of MW/UV system, that is, the presence of Fe (II/III) inhibited ENRO degradation; without Fc (II/III), the removal rate of TOC was 70.1% after 120 minutes of MW/UV (02, pH=3.0). When different concentrations of Fe (II/III) were added, the removal rate of TOC in the reaction solution was reduced, and at the optimum chelation ratio concentration (about 0.10 m). The results showed that the presence of Fe (II/III) also inhibited ENRO mineralization in MW/UV process.
【学位授予单位】：北京交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X703
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