基于尖晶石型铁氧体的高级氧化技术在有机废水处理中的应用

随着我国经济的快速发展和城市化进程的加快,自然水体中的有机污染问题愈加严重。基于自由基反应的高级氧化技术(AOPs)可以高效去除水环境中残留的难生物降解的有机污染物,在催化剂的作用下,高级氧化过程方能有效生成强氧化性的自由基来降解有机污染物。尖晶石型铁氧体(MFe₂O₄(M=Zn, Ni, Co, Cu, Mn))被广泛用作高级氧化过程中驱动自由基生成的催化剂,同时强磁性及高稳定性保证其容易在外加磁场的作用下实现回收和再利用。本文主要综述了基于尖晶石型铁氧体的非均相类芬顿技术、光催化技术及过硫酸盐高级氧化技术在有机废水处理方面的研究进展,着重介绍了不同铁氧体磁性纳米材料在上述3种高级氧化技术中催化降解水体中有机污染物的作用机制以及催化性能增强的途径;最后指出尖晶石型铁氧体在高级氧化技术应用中存在的一些问题,并对其后续研究方向进行展望。     

多相催化过硫酸盐工艺处理水环境中有机污染物的非自由基过程

20世纪80年代至今,水处理技术中的高级氧化过程(AOP)已被广泛研究及应用。然而水体中的有机污染物仍因种类繁多和降解难易不同困扰着研究者们,因此对于AOP的机理过程需要更深入的分析认识,以利于技术的进一步发展及应用。AOP中的过硫酸盐氧化工艺近年来得到大量关注,其自由基机理的关键活性物种是·OH 和·SO₄^-。非自由基机理分为¹O₂氧化和PS直接氧化(也称电子转移),某些体系中高价态金属也直接或间接地参与氧化过程。但非自由基过程的发生机理及优势特点仍存在争议。本文综述了基于多相催化过硫酸盐高级氧化过程处理水中有机污染物的最新研究,阐述反应机理及其分析手段,并指出当前研究可能存在的问题。对于过硫酸盐高级氧化工艺中非自由基过程的未来研究方向及应用前景提出展望。     

基于硫酸根自由基的先进氧化活化方法及其在有机污染物降解上的应用

基于硫酸根自由基(SO₄^.-)的先进(高级)氧化法(AOPs)因其对新型有机污染物的高降解能力和高适应性而受到越来越多的关注。相比羟基自由基(·OH),SO₄^.-的选择性更好、还原电位更高、半衰期更长、pH范围更宽且成本更低,因而能更有效的降解污染物。SO₄^.-可由过一硫酸盐(PMS)或过二硫酸盐(PDS)等过硫酸盐(PS)通过热、机械化学、过渡金属、碳质材料、碱、紫外(UV)或电化学等方法活化产生。本文分析了不同活化方法的优缺点及其应用于有机污染物降解上的研究进展,总结了SO₄^.-降解含不同官能团污染物的三种机理(加成作用、夺氢作用和直接电子转移),并综述了SO₄^.-降解持久性有机污染物(POPs)、“伪持久性有机污染物”——药物和个人护理品(PPCPs)及有机染料三大类有机污染物的降解途径、降解产物及其研究进展,最后展望了该技术未来的研究方向。     

非贵金属催化电极Ni/C@CF的制备及绿色类Fenton性能

传统芬顿(Fenton)法利用Fe²⁺催化H₂O₂产生具有强氧化性的羟基自由基(·OH),可以高效氧化降解水中有机污染物,但其操作pH范围窄(pH≈3)和易产生铁絮凝沉淀的缺点限制了其应用发展.原子氢H*作为一种单电子供体,可以将电子快速转移到H₂O₂中,生成·OH,适用于广泛的pH值,没有铁污泥产生,是一种新型高效绿色芬顿法.然而,原子H*更易相互结合形成H₂,极不稳定,因此,探索合适的电催化剂对H*绿色Fenton的应用起着至关重要的作用.本文以炭黑作为载体,通过液相还原法制备了具有催化活性高、性能稳定的Ni/C@碳毡(Ni/C@CF)非贵金属电催化材料,制备的Ni纳米粒子均匀分散在炭黑上.以此电极材料为阴极,构建绿色Fenton催化体系,能够催化H₂O和H+生成H*,进而催化H₂O₂产生·OH,高效降解去除水中抗生素污染物.通过调节制备方法、电压、溶液pH值及外加氧化剂量,确定了该体系...     

电-Fenton及类电-Fenton技术处理水中有机污染物

传统Fenton技术是一种广泛用于水体里有机污染物降解的高级氧化技术(advanced oxidation technologies, AOTs)。它利用Fenton试剂Fe²⁺与H₂O₂反应生成具有强氧化性的羟基自由基(^·OH),从而降解有机污染物。基于相似的机理,过渡金属离子(Fe²⁺、Co²⁺和Ag⁺等)也可与过硫酸盐反应生成氧化能力较强的硫酸根自由基(SO₄^·-),而被称之为类Fenton技术。传统Fenton技术存在Fe²⁺投加量多,产生的铁污泥多等缺点,因此,有学者将Fenton技术与电化学技术结合,使Fe²⁺在阴极得以持续再生,这就是广为关注的电-Fenton技术。同样地,类Fenton技术也遇到与传统Fenton技术相似的问题。借鉴电-Fenton技术的成功应用,基于硫酸根自由基的类电-Fenton技术应运而生。本文在介绍电-Fenton和类电-Fenton技术原理的基础上,概括了电-Fenton和类电-Fenton技术的主要类型及其改进方法,并就值得深入研究的问题和热点趋势进行了展望。     

纳米TiO2异相光催化降解2,6-二甲酚中间过程的UV吸收光谱和荧光光谱示踪研究

用半导体纳米材料(如TiO₂,SnO₂,CdS等)进行光降解消除污染物因其能最大限度利用太阳能和降解完全(有机质最终全部转化为CO₂,H₂O等)以及降解速率高的特点被认为是环境科学的新领域。异相光催化降解是有机物作为电子供体捕获TiO₂表面光生空穴自身被氧化降解的过程,因TiO₂价带空穴所具有强的氧化性,一般有机物都可进行光化学反应^[1]。这一过程总是以一系列的中间反应步骤所构成,中间体形成的峰形动力学曲线及其异于原初态的光谱特性对揭示光催化降解动力学过程至为重要。本文主要对2,6-二甲酚-纳米TiO₂悬浮体系光降解动态分子光谱进行示踪研究。     

光电协同效应降解饮用水中邻氯酚的机理与动力学

要 在集成光解电解一体化反应器中, 以邻氯酚(2-CP)为模型污染物, 通过产物和动力学分析详细探讨了光电复合作用的协同效应机理, 建立了光电复合作用的动力学模式. 表观动力学常数的对比表明复合协同作用对于总有机碳(TOC)的去除具有显著的协同效应. 研究表明, 光电复合作用在研究条件下对污染物的降解具有多层次、多途径的互补效应, 降解反应的途径不止是单独的光解与电解途径的简单累加, 而是通过新的作用途径组合构成光电协同效应. 通过紫外光辐射激发和定向直流电场作用控制电极中毒和污染物分子的激发态及其迁移趋势, 从而大大提高了降解反应的效率. 通过光电复合作用能够触发构成高级氧化的多种自由基链反应, 从而取得水中有机污染物的快速、完全的矿化. 动力学分析表明, 光电协同作用在溶液中形成的羟基自由基(OH·)反应是去除TOC的主要途径.     

钠盐溶液中U(Ⅵ)的电化学电子转移与晶化研究

采用循环伏安法分析钠盐溶液中U(Ⅵ)的电化学行为, 恒电位电化学还原处理U(Ⅵ), 利用交流阻抗谱分析电化学还原反应中的过程动力学特性, 利用X射线衍射、 扫描电子显微镜和电子能谱等方法分析了U(Ⅵ)的电化学晶化. 结果表明, 在钠盐溶液中, U(Ⅵ)可通过电化学反应先还原成低价的U(V)并进一步还原为U(Ⅳ), U(Ⅳ)一步氧化为U(Ⅵ), U(Ⅳ)/U(Ⅵ)之间的电化学转化过程受扩散控制, 且U(Ⅵ)的电化学电子转移易受环境pH值的影响; 恒电位还原4 h时, 溶液中U(Ⅵ)的去除率可达90%, U(Ⅵ)的结晶固化产物主要以固态的(UO₂)₆O₂(OH)₈·6H₂O(水铀矿) 和UO₂的形式附着在工作电极上.     

活性炭催化过氧化物高级氧化技术降解水中有机污染物*

活性炭（AC）能够催化过氧化氢(H₂O₂）释放出强氧化性的羟基自由基•OH。过二硫酸盐（PS）与H₂O₂结构上相似,因此PS也有可能被AC催化产生强氧化性的硫酸根自由基SO4−•。AC催化无机过氧化物（H₂O₂或PS）将发展成为一类新型高级氧化技术。AC催化H₂O₂联合体系包括AC/H2O2,AC/Fenton,AC/H₂O₂/紫外光,,AC/H₂O₂/微波,AC/湿式H₂O₂氧化;AC催化AC/PS联合体系包括 AC/PS,AC/PS/金属离子, AC/PS/ 微波。AC过氧化联合体均可高效降解水中有机污染物。本文在首次综述AC/过氧化物联合体系处理有机污染物研究现状的基础上,分析了AC和过氧化物的相互作用,并对该类高级氧化技术的发展前景进行了展望。     

g-C3N4/Bi8(CrO4)O11S型异质结的自组装制备及其光催化降解诺氟沙星和双酚A(英文)

近年来,抗生素的过度使用导致水体严重污染,威胁着生态环境安全和人体健康.太阳光驱动的半导体光催化技术被认为是一种有效去除污染物的手段.由于单一半导体光催化剂的多种缺陷,构建具有可见光响应和强氧化/还原能力的异质结光催化剂是去除有机污染物的有效途径.Bi₈(CrO₄)O₁₁(BCO)作为一种新发现的可见光响应半导体,由于较正的价带位,使得其在光催化污染物降解和水氧化方面显示了潜在的应用价值.然而,快速的载流子复合抑制了其活性.石墨相氮化碳(g-C₃N₄,CN)作为不含金属的半导体备受关注,其不仅具有可见光响应、环境友好和电子结构可调等优点,而且二维结构和较负的导带位使得CN更容易与其它半导体形成异质结光催化剂.因此,氧化型的BCO和还原型的CN结合构成异质结,有望形成S型载流子转移,从而提高光生电子-空穴对的分离效率,进而提高光催化降解污染物的活性.本文通过自组装方法制备了一系列新型CN基异质结CN/BCO.CN/BCO异质结光催化降解诺氟沙星(NOR)和双酚A(BPA)的最优比...     

Detection and characterization of olmutinib reactive metabolites by LC–MS/MS: Elucidation of bioactivation pathways

Olmutinib (Olita?) is an orally bioavailable third generation epidermal growth factor receptor tyrosine kinase inhibitor. Olmutinib was approved in South Korea in May 2016 for the treatment of patients suffering from locally advanced or metastatic epidermal growth factor receptor T790M mutation‐positive non‐small cell lung cancer. Reactive olmutinib intermediates may be responsible for the severe side effects associated with the treatment. However, literature review revealed no previous reports on the structural identification of reactive olmutinib metabolites. In this work, the formation of reactive olmutinib metabolites in rat liver microsomes was investigated. Methoxylamine, glutathione, and potassium cyanide were used as capturing agents for aldehyde, iminoquinones, and iminium intermediates, respectively. The stable complexes formed were identified using liquid chromatography–tandem mass spectrometry. The major phase I metabolic pathway observed in vitro was hydroxylation of the piperazine ring. Seven potential reactive intermediates were characterized, including three iminium ions, three iminoquinones, and one aldehyde. Based on the findings, various bioactivation pathways were postulated. Hence, identifying the reactive intermediates of olmutinib that may be the cause of severe side effects can provide new insights, leading to improved treatments for patients.     

Some new aspects of benzyne and radical mediated cyclisations

KNH₂/NH₃ cyclisations of some alkoxy substituted arylhalides proceed in poor yields. This shortcoming may be overcome by the use of LDA/THF to effect the ring closure which may occur through benzyne or radical intermediates. Besides ortho halogenated dihydroanils and amides, the cyclisation of the benzylamine Schiff bases also provides a convenient route to isoquinoline alkaloids.     

Novel synthetic approach to alfaprostol key intermediates via Stille coupling with an alkyne

Novel intermediates based on the Corey skeleton for preparation of the ω-chain of non-halogenated unnatural prostaglandin analogues containing a triple bond at position 13–14 (PG numbering) were synthesized. The utilization of a novel synthetic approach towards a new tin intermediate, and subsequent Stille coupling opens up new possibilities for preparing these important pharmaceutical intermediates.     

Characterization of a Thiolato Iron(III) Peroxy Dianion Complex

Nucleophilic oxidant: The reaction between a thiolato iron(II) complex 1 and superoxide in aprotic solvent at -90?°C yields a novel thiolato iron(III) peroxide intermediate 2, which exhibits unusually high nucleophilic reactivity. Compound 2 is an isomer of the thiolato iron(II) superoxide intermediate that is invoked in the reaction between superoxide reductase and superoxide.     

Harnessing [1,4], [1,5], and [1,6] Anionic Fries-type Rearrangements by Reaction-Time Control in Flow

A series of anionic Fries-type rearrangements of carbamoyl-substituted aryllithium intermediates were controlled by using flow microreactor systems. For the [1,4] and [1,5] rearrangements, the aryllithium intermediate formed before carbamoyl migration and the lithium alkoxide formed after carbamoyl migration can be selectively subjected to subsequent reactions with electrophiles by precisely controlling the residence time and temperature (−25 to −50 °C). In contrast, the [1,6] rearrangement is rather slow even at −25 °C. The absence of crossover products indicates the intramolecular nature of the carbamoyl group migration.     

Deactivation of Cationic CuI and AuI Catalysts for A3 Coupling by CH2Cl2: Mechanistic Implications of the Formation of Neutral CuI and AuI Chlorides

Care should be exercised when using CH₂Cl₂ as a solvent for reactions in which amines are a reagent, since undesirable deactivation of cationic copper(I) and gold(I) catalysts to form the corresponding inactive neutral chloride complexes [LMCl] (M=Cu or Au) can occur as a result of the generation of hydrogen chloride in the medium. Cu^I and Au^I deactivation has been proved for the Mannich three‐component coupling reaction. A series of Cu^I and Au^I complexes with potential mechanistic implications were isolated and characterized by X‐ray crystallography.     

The role of 2,3-dimethylene-1, 4-cyclohexadiyl diradical as a reactive intermediate in some rearrangement reactions

Quantum chemical CI calculations with the semiempirical MO method SINDO1 are performed to study the rearrangement reactions of 1,2,6,7-octatetraen, 2,3-dimethylenebicyclo(2.2.0)hexane, 3,4-dimethylene-1,5-hexadiene and bicyclo(4.2.0)octa-1,5-diene. It is shown that the most favorable pathway of each of these six rearrangements involves the 2,3-dimethylene-1,4-cyclohexadiyl diradical as an interceptable intermediate. Two further intermediates, 1,2-divinyl-1-cyclobutene and 1,2-divinylylcyclobutane appear, but the latter with little importance. Energies and geometries of the four reactants resp. products, the three intermediates and twelve transitions states are presented. The mechanism of the rearrangements is discussed.     

Electronic structure of unstable intermediates

The geometry of the species OCC has been investigated within the restricted Hartree-Fock LCAO-MO-SCF approximation. Several one electron properties have been calculated at the calculated minimum energy configuration of R(O-C)=2.121 bohr, R(C-C)=2.58 bohr.     

Are Oxazolidinones Really Unproductive,Parasitic Species in Proline Catalysis? – Thoughts and Experiments Pointing to an Alternative View

The N,O‐acetal and N,O‐ketal derivatives (oxazolidinones) formed from proline, and aldehydes or ketones are well‐known today, and they are detectable in reaction mixtures involving proline catalysis, where they have been considered ‘parasitic dead ends’. We disclose results of experiments performed in the early 1970's, and we describe more recent findings about the isolation, characterization, and reactions of the oxazolidinone derived from proline and cyclohexanone. This oxazolidinone reacts (THF, room temperature) with the electrophiles β‐nitrostyrene and chloral (=trichloroacetaldehyde), to give the Michael and aldol adduct, respectively, after aqueous workup (Scheme 5). The reactions occur even at ?75° when catalyzed with bases such as 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU) or EtN(i‐Pr)₂ (DIPEA) (10%; Table 1). It is shown by NMR (Figs. 1 and 3) and IR analysis (Figs. 2 and 4) that the primarily detectable product (before hydrolysis) of the reaction with the nitro‐olefin is again an oxazolidinone. When dissolved in hydroxylic solvents such as MeOH, ‘hexafluoroisopropanol’ ((CF₃)₂CHOH; HFIP), AcOH, CF₃COOH, or in LiBr‐saturated THF, the ring of the oxazolidinone from cyclohexanone and proline opens up to the corresponding iminium ion (Tables 2–4), and when treated with strong bases such as DBU (in (D₈)THF) the enamino‐carboxylate derived from proline and cyclohexanone is formed (Scheme 8). Thus, the two hitherto putative participants (iminium ion and enamine) of the catalytic cycle (Scheme 9) have been characterized for the first time. The commonly accepted mechanism of the stereoselective C,C‐ or C,X‐bond‐forming step (i.e., A – D ) of this cycle is discussed and challenged by thoughts about an alternative model with a pivotal role of oxazolidinones in the regio‐ and diastereoselective formation of the intermediate enamino acid (by elimination) and in the subsequent reaction with an electrophile (by trans‐addition with lactonization; Schemes 11–14). The stereochemical bias between endo‐ and exo‐space of the bicyclo[3.3.0]octane‐type oxazolidinone structure (Figs. 5 and 6) is considered to possibly be decisive for the stereochemical course of events. Finally, the remarkable consistency, with which the diastereotopic Re‐face of the double bond of pyrrolidino‐enamines (derived from proline) is attacked by electrophiles (Schemes 1 and 15), and the likewise consistent reversal to the Si‐face with bulky (Aryl)₂C‐substituents on the pyrrolidine ring (Scheme 16) are discussed by invoking stereoelectronic assistance from the lone pair of pyramidalized enamine N‐atoms.     

Photocatalytic water purification: Destruction of resorcinol by irradiated titania

Ethanedial, butanoic acid anhydride and trihydroxybenzenes have been determined as intermediates of resorcinol photocatalytic oxidation. The photoreaction rate shows a 1st order dependence on resorcinol concentration. The calculated reaction rate constant is 2.1×10⁻⁸ mol dm⁻³ s⁻¹, which is similar to the rate constant of phenol photocatalytic oxidation on TiO₂ reported beore.