Degradation of methotrexate by UV/peroxymonosulfate: Kinetics,effect of operational parameters and mechanism

Methotrexate (MTX) is one of the most consumed anti-cancer drugs in the pharmaceutical market around the world. The widespread occurrence of MTX in aquatic environment through hospital effluent has attracted increasing concern due to its potential to induce water pollution. In the present study, the degradation of MTX in aqueous medium was investigated by UV-activated peroxymonosulfate (PMS). A significant improvement in degradation rate by increasing UV intensity and PMS concentration while the decrease in degradation efficiency with the increase of solution pH and initial concentration of MTX was observed. The proposed UV/PMS process could achieve more than 90% MTX degradation in 30 min with a good mineralization degree (65%). A pseudo-first order kinetic model was employed and successfully predicted the degradation of MTX. The effect of other operational parameters such as the initial concentration of the targeted compound, dosage of oxidant (PMS), solution pH and UV intensity on the degradation rate were investigated. At the last, the main transform intermediates were identified using LC–MS and possible degradation pathways were proposed. The results show that UV/PMS can be used as an efficient technology to treat pharmaceuticals such as methotrexate containing water and wastewater.     

UV/oxone降解水中甲氧苄啶的效能及模型评价

研究采用UV、oxone、UV/oxone共3种工艺降解甲氧苄啶（TMP）的效果及动力学。采用响应面曲线法研究含有HCO₃ ^-、Cl^-、NO₃ ^-和pH四因素、三水平的水体条件下UV/oxone对TMP的降解效果及模型,并选用4种实际水源水体为水质背景来评价模型预测值与实际降解值的差别,最后比较了3种工艺的同等降解率条件下的降解效能。结果发现UV和oxone单独降解TMP时仅降解了5.5%和62.0%,而UV/oxone可达到93.2%,且降解过程符合拟一级反应动力学,动力学常数为0.1768min^-1。采用相对速率法可得到?SO₄ ^–与TMP的反应速率常数为2.07×10⁸L/(mol·s)。通过响应面曲线法得到UV/oxone降解TMP的回归方程式,对应的p值小于0.0001,拟合缺失项P不显著（0.9726>0.05）,校正决定系数R ²=0.82＞0.8,说明该模型可信度高,采用实际水体进行模型验证后发现实际降解值基本符合模型预测值。降解率一定的条件下UV/oxone耗时最短,是一种高效、快速、可行的降解工艺。     

UV/H2O2降解活性黑5动力学研究

建立一种双曲线模型对UV/H2O2降解偶氮染料活性黑5过程进行描述,考察不同H2O2初始浓度对活性黑5去除率、瞬态.OH浓度和反应速率的影响,并利用液相色谱质谱联用分析降解中间产物。结果表明:最佳的H2O2投加量是8.824 mM,50 min后活性黑5的去除率可达94%以上。双曲线模型能较好地描述UV/H2O2降解活性黑5过程,利用该模型可估算反应过程中瞬时.OH的浓度和瞬时反应速率。     

CNTs/PMS高级氧化体系去除水中的环丙沙星

针对当前抗生素废水处理的难题,以环丙沙星（CIP）为研究对象,采用碳纳米管（CNTs）活化过硫酸氢盐（PMS）对其进行降解。考察了PMS浓度、CIP浓度、CNTs投加量、初始pH等因素对CIP降解效果的影响。研究结果表明,在pH为2.73～11.38范围内,PMS的浓度为1.5mmol/L、CNTs投加量为15mg/L时,初始浓度为5mg/L的CIP降解效果达到最佳,CNTs在反应过程中集吸附和催化于一体,且作为催化剂可实现多次循环利用。借助电子顺磁共振捕获技术和自由基猝灭反应对降解过程中的活性物质进行分析与鉴定,实验结果表明,在整个反应体系中起主导作用的活性基团是硫酸根自由基（SO₄ ^?-）。通过中间产物分析,发现氧化反应主要发生在哌嗪基团、喹诺酮核心的C－F键及环丙烷环上。这些结果可应用于抗生素废水的工业处理。     

亚硝酸盐共存下UV/PS/CNTs降解 2,6-二氯苯酚及其机理

以2,6-二氯苯酚（2,6-DCP）为目标污染物，在亚硝酸盐（NO2-）共存背景下采用紫外协同碳纳米管复合活化过硫酸盐工艺（UV/PS/CNTs）降解2,6-DCP，探究其影响因素及降解机理，考察体系循环活化潜能和副产物生成情况。结果表明，在反应时间30 min、反应温度25 ℃、2,6-DCP浓度为0.05 mmol/L、NO2-浓度为0.2 mmol/L、PS投量为0.5 mmol/L、CNTs投量为50 mg/L时，UV/PS/CNTs体系对2,6-DCP降解率达95.9%。该体系中，2,6-DCP降解速率随PS和CNTs浓度的增加而增大，随NO2-浓度增大而减小，溶液pH对目标物降解呈先增大后减小趋势，pH 9.0时降解率达99.8%，降解速率为0.3483 min-1。CNTs具有良好的循环使用性能，5次重复实验后仍能去除89.0%的2,6-DCP，且在实际水体中降解效果较好。机理分析表明，该体系对2,6-DCP降解遵循以单线态氧为主导的非自由基氧化途径，且反应过程中生成了一氯硝基酚副产物。     

LaCoO3钙钛矿活化过一硫酸盐降解萘普生

在催化活化过一硫酸盐(PMS)降解水中污染物的反应中,通过添加钴基钙钛矿提高反应效率。利用溶胶凝胶法制备了LaCoO₃钙钛矿,通过实验评估LaCoO₃/PMS体系对非甾体抗炎药萘普生（NAP）的降解效果。分析了LaCoO₃投加量、PMS投加量、反应初始pH、Cl^-浓度和腐殖酸（HA）对NAP去除率的影响以及该体系的矿化能力。结果表明NAP降解的反应速率随LaCoO₃和PMS投加量增加而增大;反应初始pH在5.0时NAP降解效果最好;溶液中存在Cl^-对降解有促进效果,且Cl^-浓度越大促进效果越明显;腐殖酸（HA）对反应有一定程度的抑制效果;LaCoO₃在重复利用5次时仍有较好的稳定性。此外,自由基淬灭实验结果表明在LaCoO₃/PMS体系中SO₄^·-为主要活性物质。     

Evaluation of Degradation Characteristics of Reactive Dyes by UV/Fenton,UV/Fenton/Activated Charcoal,and UV/Fenton/TiO2 Processes: A Comparative Study

The photochemical decolorization and mineralization of Reactive red 241 (RR241) in aqueous solution has been studied using a homogeneous photofenton process and its combination with activated charcoal and titanium dioxide. The effects of applied catalyst and adsorbent loading, dye concentrations, pH of solution, and the effect of various systems at constant UV irradiation were determined. Decolorization, COD and TOC analysis were employed to evaluate the results of the photochemical and photocatalytic degradation of RR241. The degradation of the dye was monitored by constant COD analysis and then analyzed by high performance liquid chromatography (HPLC) and IR analysis. The result shows that complete decolorization of dye with photofenton process required 240 minutes with 18.6% of maximum TOC reduction. To overcome the problem of slow decolorization and low degradation with photofenton process, it was combines with activated charcoal and Titanium dioxide. UV/Fenton/AC process gave complete decolorization in less than 80 minutes with 14.9% of TOC reduction after 240 minutes. In contrast the UV/Fenton/TiO₂ process required 120 minutes for complete decolorization but yielded maximum TOC reduction of 43.9% after 240 minutes. Therefore, according to COD and TOC reduction it could be suggested that the UV/Fenton/TiO₂ was more effective than other processes.     

紫外/亚硫酸钠体系对2,4,6-三溴酚的脱溴效果及机理

研究了紫外/亚硫酸钠（UV/SO₃^2-）体系对2,4,6-三溴酚（2,4,6-TBP）的脱溴效果及影响因素,分析了还原体系2,4,6-TBP的脱溴过程、降解机理及降解路径。结果表明：UV/SO₃^2-还原体系对2,4,6-TBP的降解效果明显高于单独UV体系;亚硫酸钠浓度、pH与反应温度均对还原体系目标污染物的降解影响显著。随着亚硫酸钠浓度升高、pH上升及反应温度提高,UV/SO₃^2-体系2,4,6-TBP的降解效果逐渐增加。准一级动力学方程可描述不同亚硫酸钠浓度与反应温度时还原体系对目标污染物的降解过程。水合电子捕获剂的添加可有效抑制2,4,6-TBP的脱溴反应;UV/SO₃^2-体系污染物还原降解速率与溴离子产生率均高于单独UV体系。还原体系中2,4,6-TBP在水合电子作用下逐级脱溴降解为低毒性物质。     

Ozonation,Ozone/UV and UV/H2O2 Degradation of Chlorophenols

The performance of the O₃, O₃/UV and UV/H₂O₂ processes for degradation of six chlorophenols (4-chlorophenol, 2-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol, 2,3,4,6-tetrachlorophenol and pentachlorophenol) were studied in laboratory reactors. Comparative study showed that chlorophenols can be degraded successfully by all of the methods studied, whilst traditional ozonation at high pH was determined to be the most effective method to treat chlorophenols. Even though the molar absorptivity of chlorophenols is known to be relatively high in the UV-region, the combination of UV-radiation with ozone did not accelerate the degradation of chlorophenols further. The toxicity of degradation products formed during ozonation of chlorophenols has been compared with the toxicity of pure chlorophenols utilizing Daphnia magna 24 hours test. Ozonation of chlorophenols yielded less toxic or even nontoxic products for Daphnia magna compared with parent compounds.     

非均相UV/Fenton催化降解苯酚研究

研究了UV/H2O2/改性海藻酸铁非均相催化降解苯酚时H2O2的投加量、溶液初始pH、苯酚初始浓度、改性海藻酸铁的含铁量等因素对苯酚降解率的影响.结果表明:该非均相体系在pH 2.0～11.1范围内都能高效催化氧化降解不同浓度苯酚废水.在基准条件下,若增加改性海藻酸铁的含铁量,则在反应时间2 min时,苯酚降解率可接近100%;以日光代替紫外光,苯酚降解率仍可达68.9%.     

Co2+活化过硫酸盐降解水中的磺胺甲噁唑

为了探究并优化钴离子(Co2+)活化过一硫酸盐(PMS)对水中抗生素的去除能力,以典型抗生素磺胺甲恶唑(SMX)为目标物,研究了反应体系对SMX的降解情况.考察了 Co2+投量、SMX浓度、PMS投量、温度和pH等因素对SMX降解效能的影响,并对反应体系的总有机碳(TOC)和活性物种进行分析.结果表明,常温条件下,Co...     

Study of Degradation Kinetics and Structural Analysis of Related Substances of Ceftobiprole by HPLC with UV and MS/MS Detection

Ceftobiprole is a novel β-lactam antibiotic, active against methicillin-resistant Staphylococcus aureus, vancomycin-resistant S. aureus and penicillin-resistant Streptococcus pneumoniae. To artificially generate potential degradation products (DPs) of ceftobiprole that may be formed under relevant storage conditions, acidic, alkaline, oxidative, photolytic and thermolytic stress tests were performed in both solution and solid state. A novel selective HPLC method was developed for the separation of ceftobiprole from its DPs and synthesis by-products (SBPs) using Kinetex Biphenyl column, ammonium acetate buffer pH 5.8 and acetonitrile. The kinetic studies demonstrated the low stability of ceftobiprole in alkaline solution, in the presence of an oxidising agent and under irradiation with near UV. In the solid state, ceftobiprole underwent oxidation when the powder was irradiated with visible light and UV. Based on mass spectroscopic analysis, 13 new structural formulas of SBPs and DPs were proposed, along with molecular formulas for three other DPs obtained in solution and four oxidative DPs characteristic of solid-state degradation.     

Photocatalytic degradation of 2,4-dichlorophenol by TiO2/UV: Kinetics, actinometries and models

Heterogeneous photocatalysis has proved to be a useful tool for the degradation of water pollutants as it can be observed by the high number of references appeared the last 30 years. Despite this strong research, some points, as more satisfactory and accurate kinetic models, still have to be more developed. In this work, as reaction model, the photocatalytic treatment of 2,4-dichlorophenol has been studied by using TiO₂ in suspension as catalyst. The influence of different variables (TiO₂ concentration, pH effect, radiation) on the reaction rate has been tested. Afterwards, two new kinetic models are proposed. The first one takes into account the effect of intermediates in the degradation rate of the parent pollutant, which allows a better agreement for long time reactions. The second one attempts to include the radiation effect into the kinetic expression by means of a new term which refers to the absorbed light by the photocatalyst. Both models fit quite well with the experimental data and seem to be interesting future tools for the comparison and scaling-up of different photocatalytic systems.     

基于UV/H_2O_2和UV/PS工艺降解水体中磺胺吡啶研究

采用高级氧化技术-紫外/双氧水(UV/H_2O_2)和紫外/过硫酸盐(UV/PS)工艺降解磺胺吡啶(SPY)。研究表明,紫外与氧化剂(H_2O_2、PS)联用可显著提高去除率,其反应符合拟一级动力学模型。目标污染物磺胺吡啶的去除率在一定浓度内随着氧化剂H_2O_2和PS浓度升高而升高;磺胺吡啶初始浓度越大,反应速率越小;UV/H_2O_2工艺降解磺胺吡啶最大去除率发生在p H=3,而UV/PS工艺降解SPY在p H=11时去除率最大;Na Cl会抑制UV/H_2O_2和UV/PS工艺对目标污染物的降解,而适当的Na HCO_3可促进降解反应的进行;腐植酸对UV/PS工艺产生抑制作用,低浓度腐植酸(≤1 mmol/L)对UV/H_2O_2工艺则有促进作用。     

基于UV/H_2O_2和UV/PS工艺降解水体中磺胺吡啶研究

采用高级氧化技术-紫外/双氧水(UV/H_2O_2)和紫外/过硫酸盐(UV/PS)工艺降解磺胺吡啶(SPY)。研究表明,紫外与氧化剂(H_2O_2、PS)联用可显著提高去除率,其反应符合拟一级动力学模型。目标污染物磺胺吡啶的去除率在一定浓度内随着氧化剂H_2O_2和PS浓度升高而升高;磺胺吡啶初始浓度越大,反应速率越小;UV/H_2O_2工艺降解磺胺吡啶最大去除率发生在p H=3,而UV/PS工艺降解SPY在p H=11时去除率最大;Na Cl会抑制UV/H_2O_2和UV/PS工艺对目标污染物的降解,而适当的Na HCO_3可促进降解反应的进行;腐植酸对UV/PS工艺产生抑制作用,低浓度腐植酸(≤1 mmol/L)对UV/H_2O_2工艺则有促进作用。     

O3/UV,O3/TiO2/UV,O3/VO2/TiO2降解磺基水杨酸

实验利用O3/UV,O3/TiO2/UV,O3/VO2/TiO2降解了磺基水杨酸.结果表明,在这三种高级氧化技术中,O3/VO2/TiO2的氧化效果最好,如在相同的条件下,30 min后取样表明三者COD的去除率分别为47%,55%和70%.在不同pH条件下研究表明O3/TiO2/UV对水体pH的影响较为敏感.通过加入自由基猝灭剂研究表明三者产生羟基自由基的活性顺序是O3/VO2/TiO2＞O3/TiO2/UV＞O3/UV.     

Degradation of Sulfosalicylic Acid by O3/UV O3/TiO2/UV,and O3/V-O/TiO2 : A Comparative Study

Chemical oxygen demand (COD) removal rates of sulfosalicylic acid (SSal) degraded by three advanced oxidation processes (AOPs): O₃/UV, O₃/TiO₂/UV and O₃/V-O/TiO₂ are compared in this paper. (V = Vanadium). The results show that O₃/V-O/TiO₂ is the most effective process among three AOPs and the order of degradation efficiencies at different pH values is shown as O₃/V-O/TiO₂ > O₃/TiO₂/UV > O₃/UV. For example, at the buffered solution of pH 6.8, the COD removal rate of O₃/V-O/TiO₂ reaches 70% in 30 minutes, but those of O₃/TiO₂/UV and O₃/UV are 55% and 47% at the same conditions, respectively. Furthermore, the effect of CO₃ ^{2 ?}on the COD removal rates of three AOPs shows that O₃/V-O/TiO₂ and O₃/TiO₂/UV may be considerable promising methods to overcome the limitation of the presence of radical scavenger in solution. Both the adsorption of SSal on catalysts and other oxidants (atom oxygen, photo-generated hole) must be responsible for the above result.     

热降解动力学方法研究ABS的降解机理

在空气气氛下,采用热重分析(TGA)研究了不同升温速率下丙烯腈-丁二烯-苯乙烯共聚物（ABS）的热降解过程,分别使用Flynn-Wall-Ozawa法和Kissinger法对降解过程进行动力学分析。结果表明,ABS降解包含2个阶段,350~450 ℃之间发生降解反应,同时伴有交联反应,降解活化能（Ea）在200 kJ/mol左右,转化率在80 %~90 %时发生炭化反应,Ea提高到262.81 kJ/mol;500~600 ℃之间是残炭的氧化,Ea降低到130 kJ/mol左右,炭层稳定性较差。ABS的降解过程反应级数为0.946,降解受到随机成核与生长机理控制,降解在ABS基体内进行,而不是表面,所以降解气体燃烧不完全,易产生黑烟和熔融滴落。     

Heterogeneous activation of peroxymonosulfate by supported cobalt catalysts for the degradation of 2,4-dichlorophenol in water: The effect of support, cobalt precursor, and UV radiation

In order to generate sulfate radicals (SRs) as oxidizing species for the degradation of 2,4-dichlorophenol (2,4-DCP) in water, we explored heterogeneous activation of peroxymonosulfate (PMS) by supported cobalt catalysts. More attention was given to the effect of support materials (Al₂O₃, SiO₂, TiO₂) and cobalt precursors (Co(NO₃)₂, CoCl₂, CoSO₄) on cobalt–support interaction, cobalt leaching, and reactivity of the catalysts. Especially, the feasibility of simultaneous generation of SRs and hydroxyl radicals (HRs) in PMS-Co/TiO₂ systems was first studied under ultraviolet (UV) radiation. Much lower cobalt leaching was observed in Co/Al₂O₃ and Co/TiO₂ systems than that of Co/SiO₂ most probably due to their relatively strong cobalt-support interaction. Co/TiO₂ catalyst prepared with Co(NO₃)₂, compared to CoCl₂ or CoSO₄ (where Cl⁻ and SO₄²⁻, respectively, were not completely removed upon heat treatment at 500 °C), showed strong cobalt–support interaction, and thereby exhibited negligible cobalt leaching. Under UV radiation, Co/TiO₂ at Co/Ti molar ratio of 0.001 showed significant improvement in the degradation of 2,4-DCP due to HRs. The effective generation of HRs in the system can be explained with Co(III)-mediated charge transfer from the photoinduced electrons to PMS, inducing facilitation of photoinduced electron-hole separation. However, high cobalt loading (i.e., Co/Ti molar ratio of 0.1) on TiO₂ surface exhibited negligible enhancement of 2,4-DCP transformation under UV radiation since the penetration of UV light to TiO₂ was prohibited by the cobalt.