钴催化过一硫酸氢盐降解水中有机污染物:机理及应用研究

钴/过一硫酸氢盐(Co/PMS)是为了克服Fenton技术的诸多缺陷而基于类Fenton思路(过氧化物+过渡金属)建立起来的一种高级氧化技术。该体系具有Co用量少(μg/L数量级),产生的SO 4-.氧化还原电位高,能够在广泛的pH范围(2—9)降解有机污染物,反应后不产生污泥等优点,在环境污染治理领域具有广阔的应用前景。本文从自由基链式反应、溶液pH、阴离子效应、光照条件、反应气氛及固液两相交换六个方面分析了Co/PMS体系降解水中有机污染物的机理,并在此基础上综述了Co/PMS(黑暗条件)、UV/Co/PMS、Vis/Co/PMS三类均相Co/PMS体系以及Co氧化物催化、Co负载催化两类非均相Co/PMS体系降解水中有机污染物的国内外研究进展,并就存在的问题提出了展望。     

碳酸氢盐活化的过氧化氢:一种有机废水处理的新技术（英文）

水污染问题已成为影响我国可持续发展的关键问题之一,为有效提高现有污水处理的效率及其回收利用,各种催化氧化技术受到了广泛的关注.目前发展的各类高级氧化技术在实际的应用过程中明显受到了氧化剂的利用率、催化剂的浸出、寿命及成本等问题的严重限制.因此基于新的理念、发展新的催化氧化技术仍然受到广泛的关注.最近几年,利用碳酸氢盐活化过氧化氢,应用于有机废水的降解逐渐受到环境催化领域的关注.碳酸氢盐本身是一种低毒性、广泛存在于环境及生物体系的化学物质,通过它活化过氧化氢产生过碳酸氢盐氧化剂,该氧化剂能够直接氧化有机物.同时,在各种过渡金属催化剂的存在下,通过该过碳酸氢盐可以形成氧化能力更强的各种自由基(如羟基自由基等)及高价态的过渡金属离子参与有机废水的降解.虽然传统认为碳酸盐及碳酸氢盐对高级氧化法降解有机废水不利,原因是认为它们能捕捉羟基自由基,形成氧化能力更低的碳酸根自由基.现有的研究已充分表明,较低浓度的碳酸氢盐能够加快有机废水的氧化降解,而且通常比单独使用过氧化氢效率更高,这些新的发现已明显突破了传统意义上对碳酸氢盐作用的理解.更为重要的是,在微量碳酸氢盐的存在下,其产生的微碱性环境极大地消除了负载型氧化物催化剂在废水降解过程中的金属离子流失、从而极大地延长了催化剂的寿命.该缺点是各种基于过渡金属氧化物催化剂的高级氧化技术难以广泛推广的关键性挑战,原因是随着氧化降解的进行,废水体系由于有机酸的生成而逐渐酸化,进而引发氧化物催化剂的酸溶而流失.在这点上,碳酸氢盐活化过氧化氢系统由于其天然的微碱性环境体现出了其明显的优势.本文即是在本课题组工作基础上,对该领域内国内外研究进展加以总结,以期获得国内外同行的进一步关注.综述的主要内容包括:(1)碳酸氢氧活化过氧化氢的相关知识介绍,(2)均相碳酸氢氧活化过氧化氢降解有机废水的研究进展,(3)基于金属氧化物催化剂的碳酸氢氧活化过氧化氢降解有机废水的研究进展,和(4)碳酸氢盐在其他高级氧化技术中的应用.虽然基于碳酸氢氧活化过氧化氢降解有机废水的研究还处于早期探索阶段,还有很多基础科学问题如降解机理等值得进一步探索,期望通过该综述的介绍能够让同行对碳酸氢氧活化过氧化氢降解有机废水有一个比较全面的了解,进而推动该研究方向的发展,为有机废水的催化处理提供新的机会.     

碳酸氢盐活化的过氧化氢：一种有机废水处理的新技术

水污染问题已成为影响我国可持续发展的关键问题之一,为有效提高现有污水处理的效率及其回收利用,各种催化氧化技术受到了广泛的关注。目前发展的各类高级氧化技术在实际的应用过程中明显受到了氧化剂的利用率、催化剂的浸出、寿命及成本等问题的严重限制。因此基于新的理念、发展新的催化氧化技术仍然受到广泛的关注。
　　最近几年,利用碳酸氢盐活化过氧化氢,应用于有机废水的降解逐渐受到环境催化领域的关注。碳酸氢盐本身是一种低毒性、广泛存在于环境及生物体系的化学物质,通过它活化过氧化氢产生过碳酸氢盐氧化剂,该氧化剂能够直接氧化有机物。同时,在各种过渡金属催化剂的存在下,通过该过碳酸氢盐可以形成氧化能力更强的各种自由基(如羟基自由基等) 及高价态的过渡金属离子参与有机废水的降解。虽然传统认为碳酸盐及碳酸氢盐对高级氧化法降解有机废水不利,原因是认为它们能捕捉羟基自由基,形成氧化能力更低的碳酸根自由基。现有的研究已充分表明,较低浓度的碳酸氢盐能够加快有机废水的氧化降解,而且通常比单独使用过氧化氢效率更高,这些新的发现已明显突破了传统意义上对碳酸氢盐作用的理解。更为重要的是,在微量碳酸氢盐的存在下,其产生的微碱性环境极大地消除了负载型氧化物催化剂在废水降解过程中的金属离子流失、从而极大地延长了催化剂的寿命。该缺点是各种基于过渡金属氧化物催化剂的高级氧化技术难以广泛推广的关键性挑战,原因是随着氧化降解的进行,废水体系由于有机酸的生成而逐渐酸化,进而引发氧化物催化剂的酸溶而流失。在这点上,碳酸氢盐活化过氧化氢系统由于其天然的微碱性环境体现出了其明显的优势。
　　本文即是在本课题组工作基础上,对该领域内国内外研究进展加以总结,以期获得国内外同行的进一步关注。综述的主要内容包括：(1)碳酸氢氧活化过氧化氢的相关知识介绍,(2)均相碳酸氢氧活化过氧化氢降解有机废水的研究进展,(3)基于金属氧化物催化剂的碳酸氢氧活化过氧化氢降解有机废水的研究进展,和(4)碳酸氢盐在其他高级氧化技术中的应用。虽然基于碳酸氢氧活化过氧化氢降解有机废水的研究还处于早期探索阶段,还有很多基础科学问题如降解机理等值得进一步探索,期望通过该综述的介绍能够让同行对碳酸氢氧活化过氧化氢降解有机废水有一个比较全面的了解,进而推动该研究方向的发展,为有机废水的催化处理提供新的机会。     

基于生物炭的高级氧化技术降解水中有机污染物

碳基材料催化剂因具有良好的催化性能,同时可避免金属催化剂的重金属沥出造成的二次污染问题,常被应用于高级氧化领域。其中,以废弃生物质为原材料热解产生的生物炭,不仅具有催化潜力,还具有低成本和绿色环保等优势,被广泛用于活化过氧化氢、过一硫酸氢盐和过二硫酸盐等过氧化物降解水中有机污染物。本文介绍了生物炭的前体种类和制备方法、阐述了二者对生物炭活化能力的影响,总结了生物炭活化过氧化物的机理,分析了水质对降解污染物的影响,综述了生物炭的改性、循环使用及再生,指出了这一技术存在的问题并对后续研究进行了展望。     

负载型铜钴氧化物协同催化 H2O2/HCO3-降解苯酚

近年来,环境污染特别是水的严重污染使其治理成为一个极具挑战性的课题.各种污染物复杂的化学成分和催化剂在处理过程中的浸出、寿命及成本等问题是导致众多氧化催化剂难以实际应用的主要原因.相对而言, H2O2是一种活性氧含量高、清洁并可在温和条件下使用的氧化剂,在各种高级氧化技术中受到广泛关注.而碳酸氢盐是一种弱碱性物质,在自然界及水体系中广泛存在,且无明显毒害.它可活化 H2O2,加快其氧化各种有机物,并在废水处理领域开始受到关注.该体系的明显优势在于处理体系始终处于微碱性环境,可以有效避免金属氧化物催化剂在处理过程中由于体系酸化而带来的催化剂流失,从而延长催化剂寿命,降低催化剂成本.
　　本文采用浸渍法制备了一种双金属铜、钴氧化物催化剂及相关的对照催化剂体系,利用碳酸氢盐活化 H2O2用于降解苯酚模拟废水.通过各种空白实验发现,负载于γ-Al2O3表面的钴、铜氧化物催化剂 CuO?Co3O4@γ-Al2O3具有最好的催化降解活性,而 CuO@γ-Al2O3, Co3O4@γ-Al2O3, CuO?Co3O4及 CuO和 Co3O4的物理混合物均表现出较差的催化性能.由此可见,在 CuO?Co3O4@γ-Al2O3催化剂中,铜、钴离子在苯酚降解过程中存在协同效应,这可能与催化剂中钴、铜金属离子的相互作用相关. X射线衍射和 X射线光电子能谱结果表明,反应前后 CuO?Co3O4@γ-Al2O3催化剂中金属的氧化状态并未发生改变,在使用过程中钴离子的浸出率可以忽略,铜离子的浸岀率也仅有0.6 ppm.荧光分析实验和自由基捕获实验表明,只有添加?O2-和?OH的捕获剂能明显抑制降解反应,因而推测该反应体系对有机物的降解是一个自由基氧化过程,起关键作用的可能是?O2-和?OH.     

负载型铜钴氧化物协同催化H_2O_2/HCO_3~–降解苯酚（英文）

近年来,环境污染特别是水的严重污染使其治理成为一个极具挑战性的课题.各种污染物复杂的化学成分和催化剂在处理过程中的浸出、寿命及成本等问题是导致众多氧化催化剂难以实际应用的主要原因.相对而言,H_2O_2是一种活性氧含量高、清洁并可在温和条件下使用的氧化剂,在各种高级氧化技术中受到广泛关注.而碳酸氢盐是一种弱碱性物质,在自然界及水体系中广泛存在,且无明显毒害.它可活化H_2O_2,加快其氧化各种有机物,并在废水处理领域开始受到关注.该体系的明显优势在于处理体系始终处于微碱性环境,可以有效避免金属氧化物催化剂在处理过程中由于体系酸化而带来的催化剂流失,从而延长催化剂寿命,降低催化剂成本.本文采用浸渍法制备了一种双金属铜、钴氧化物催化剂及相关的对照催化剂体系,利用碳酸氢盐活化H2O2用于降解苯酚模拟废水.通过各种空白实验发现,负载于γ-Al_2O_3表面的钴、铜氧化物催化剂CuO-Co_3O_4@γ-Al_2O_3具有最好的催化降解活性,而CuO@γ-Al_2O_3,Co_3O_4@γ-Al_2O_3,Cu O-Co_3O_4及CuO和Co_3O_4的物理混合物均表现出较差的催化性能.由此可见,在CuO-Co_3O_4@γ-Al_2O_3催化剂中,铜、钴离子在苯酚降解过程中存在协同效应,这可能与催化剂中钴、铜金属离子的相互作用相关.X射线衍射和X射线光电子能谱结果表明,反应前后CuO-Co_3O_4@γ-Al_2O_3催化剂中金属的氧化状态并未发生改变,在使用过程中钴离子的浸出率可以忽略,铜离子的浸岀率也仅有0.6 ppm.荧光分析实验和自由基捕获实验表明,只有添加·O_2~-和·OH的捕获剂能明显抑制降解反应,因而推测该反应体系对有机物的降解是一个自由基氧化过程,起关键作用的可能是·O_2~-和·OH.     

Co-Fe/SBA-15与过一硫酸盐联用非均相催化降解水中染料罗丹明B

由于硫酸根自由基(SO4?-)的强氧化性,基于SO4?-的高级氧化技术受到人们的高度关注.采用过渡金属活化过一硫酸盐(PMS)产生SO4?-用以分解有机物,反应体系简单,反应条件温和,且不需要额外的能量供给,因此,成为人们优先选用的方法,其中,采用高效、环境友好的非均相过渡金属催化剂活化PMS处理难降解有机物成为研究热点.本文研究了非均相CoFe/SBA-15-PMS体系对水中难降解染料罗丹明B(RhB)的降解.以SBA-15为载体, Co(NO3)2·6H2O和Fe(NO3)3·9H2O为前驱物,采用一步等体积浸渍法制备了CoFe/SBA-15,通过X射线衍射(XRD)、N2吸附-脱附、扫描电镜(SEM)、能谱(EDS)、透射电镜(TEM)和振动样品磁强计(VSM)等对其进行了表征.考察了焙烧温度、Co与Fe的负载量对CoFe/SBA-15催化性能的影响和该催化剂的重复使用性能,还考察了RhB降解动力学及催化剂CoFe/SBA-15投加量、氧化剂PMS投加量和反应物(RhB和PMS)初始浓度对其性能的影响,探讨了RhB的降解机理.结果表明：对于催化剂CoFe/SBA-15,合成焙烧后在SBA-15上负载的Fe、Co化合物主要是CoFe2O4复合物,它作为催化剂的活性中心负载在SBA-15的孔道内外.制备的焙烧温度对CoFe/SBA-15催化性能几乎无影响,但对Co浸出影响显著.与SBA-15相比,催化剂10Co9.5Fe/SBA-15-700(Co和Fe负载量分别为10 wt%和9.5 wt%,焙烧温度700 oC)的比表面积、孔体积和孔径均减小,分别为506.1 m2/g,0.669 cm3/g和7.4 nm,但仍然保持SBA-15的有序六方介孔结构.该催化剂以棒状体的聚集态存在,聚集体直径大于0.25μm,其磁化强度为8.3 emu/g,因此,可通过外磁铁容易地从水中分离.相比之下,10Co9.5Fe/SBA-15-700具有最佳的催化性能和稳定性,可使RhB的降解率达到96%以上, Co的浸出量小于32.4μg/L.在CoFe/SBA-15和PMS共存下, RhB的降解符合一级动力学方程, RhB降解速率随CoFe/SBA-15和PMS投加量的增加和初始反应物浓度的减小而提高.淬灭实验结果表明,在CoFe/SBA-15, PMS和RhB水溶液体系中,存在的主要活性自由基为SO4?-,它是由CoFe/SBA-15活化PMS产生的,对RhB的降解起决定性的作用. RhB降解过程的UV-vis结果表明, RhB的降解途径主要是蒽环打开, SO4?-优先攻击RhB的有色芳香烃环,然后RhB进一步分解为小分子有机物. CoFe/SBA-15循环使用10次仍能保持高催化活性和稳定性,在每次反应中RhB的降解率均大于84%, Co和Fe的浸出量均分别小于72.1和35μg/L. CoFe/SBA-15作为高效、环境友好的非均相催化剂可有效地活化PMS产生SO4?-降解水中RhB,具有实际应用的潜力.     

一步法制备铁氧化物/氮改性氧化石墨/碳纳米管异质结及其用于催化活化过一硫酸氢钾降解亚甲基蓝模型染料（英文）

随着较差的生物相容性和更高毒性有机染料的应用,如酚类化合物和抗生素,水污染和食品污染变得极其严重.这不仅危害人类健康,而且严重污染自然环境.过硫酸盐去污技术利用自由基活化降解过程,成为处理一系列污染物非常有效的方法;然而设计具有多功能性的高性能催化剂仍然面临着巨大的挑战.因此,本文借鉴铁基材料、氮改性石墨和碳纳米管独特的物化性质,以尿素、铁盐、氧化石墨、碳纳米管为原材料,通过一步水热法成功制备了三维多功能铁氧化物/氮改性氧化石墨/碳纳米管异质结,用作活化过一硫酸氢钾复合盐以降解有机模型污染物亚甲基甲蓝(MB),研究了高级氧化法(AOPs)作用机理和优化反应条件.XRD、红外光谱、SEM和XPS结果表明,铁氧化物通过物理静电作用力和化学键结合力已经被牢牢固定在了氮修饰的氧化石墨结构框架内.当加入了碳纳米管之后,它会与石墨形成类似于互穿聚合物网络的结构,从而具有三维材料的优点,且提升电子转移电导率,使得催化剂的结构和性能有了很大的改善.此外,优化了降解系统、PMS负载量、初始有机污染物浓度和催化剂用量等因素.结果表明,处于催化剂/PMS系统时,亚甲基蓝可以在12min之内有效地完全降解,可归结于碳、氮以及主要活性物质铁氧化物之间的协同作用.基于数据拟合分析,污染物氧化降解系统与拟一阶动力学相符合,其速率常数约为0.33 min~(-1).淬灭实验证明,硫酸根自由基和羟基自由基是主要的反应活性物种.这种同时富含铁/氮分级的多孔碳骨架异质结物质不仅可用作过渡金属催化剂,而且为制备其他异质结提供参考,以用于超级电容器、储能材料、电催化剂等领域     

典型无机含氧酸自由基的特性

碳酸自由基、硝酸自由基、磷酸自由基和硫酸自由基是化学反应的重要中间体，都具有氧化性，对污染物在自然和人为环境中的迁移转化会产生重要的影响.文中较为详细地介绍这几种自由基的电极电位、产生方式、检测方法及与有机物的反应方式.总结四种自由基的特性及与有机物的反应方式可发现，四种自由基和羟自由基电极电位不同，导致它们和有机物反应速率的不同；碳酸自由基并不是羟自由基去除剂，对于一些容易被氧化的化合物，碳酸自由基氧化效果比羟自由基好；四种自由基均可由羟自由基转化而来，并且这四种自由基和羟自由基与有机物反应方式基本一致，都通过电子转移、夺氢和加成的方式进行.可以预测四种自由基和羟自由基降解有机物的机理将非常相似，今后应研究四种自由基与羟自由基相互转化的规律，以及与代表性有机物的反应机理.     

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。     

CuFe2O4@GO nanocomposite as an effective and recoverable catalyst of peroxymonosulfate activation for degradation of aqueous dye pollutants

An effective and recoverable CuFe₂O₄@GO catalyst for PMS activation was synthesized and the underlying catalytic mechanism was revealed in this study.     

CuFe2O4@GO nanocomposite as an effective and recoverable catalyst of peroxymonosulfate activation for degradation of aqueous dye pollutants

Recently, heterogeneous activation of peroxymonosulfate (PMS) to oxidatively degrade organic pollutants has been a hotspot. In the present work, copper ferrite-graphite oxide hybrid (CuFe₂O₄@GO) was prepared and used as catalyst to activate PMS for degradation of methylene blue (MB) in aqueous solution. A high degradation efficiency (93.3%) was achieved at the experimental conditions of 20 mg/L MB, 200 mg/L CuFe₂O₄@GO, 0.8 mmol/L PMS, and 25 °C temperature. Moreover, CuFe₂O₄@GO showed an excellent reusability and stability. The effects of various operational parameters including pollutant type, solution pH, catalyst dosage, PMS dosage, pollutant concentration, temperature, natural organic matter (NOM), and inorganic anions on the catalytic degradation process were comprehensively investigated and elucidated. The further mechanistic study revealed the Cu(II)/Cu(I) redox couple on CuFe₂O₄@GO played the dominant role in PMS activation, where both hydroxyl and sulfate radicals were generated and proceeded the degradation of pollutants. In general, CuFe₂O₄@GO is a promising heterocatalyst for PMS-based advanced oxidation processes (AOPs) in wastewater treatment.     

Theoretical investigations on the conversions of cyclic polysulfides to acyclic polysulfide diradicals and subsequent reactions of biological interest

Sulfur is one of the most necessary biogenic elements in nature that must be assimilated by all organisms; it is an essential macronutrient for living organisms and has multiple roles in plant development. The oxidation of elemental sulfur is a complex process involving the contact of cells with sulfur particles, the oxidation of sulfur to sulfite, and the oxidation of sulfite to sulfate. To provide hypothesis concerning the most probable processes in the early states, we determined, by quantum-chemical calculations, the energies of some allotropic forms containing up to 32–40 sulfur atoms and energetics of their reactions with triplet dioxygen. The most probable reactions occurred with methylpolysulfane anions with an electron transfer to give the superoxide anion radical (and thiyls radicals) and especially the formation of peroxydic polysulfane anions. Calculations confirmed that the triplet diradical is more stable than the singlet one for acyclic polysulfide chains.     

Effects of exogenic chloride on oxidative degradation of chlorinated azo dye by UV-activated peroxodisulfate

Recently, the degradation of organic compounds in saline dye wastewater by sulfate radicals (SO₄⁻)-based advanced oxidation processes (AOPs) have attracted much attention. However, previous studies on these systems have selected non-chlorinated dyes as model compounds, and little is known about the transformation of chlorinated dyes in such systems. In this study, acid yellow 17 (AY-17) was selected as a model of chlorinated contaminants, and the degradation kinetics and evolution of oxidation byproducts were investigated in the UV/PDS system. AY-17 can be efficiently degraded (over 98% decolorization) under 90 min irradiation at pH 2.0–3.0, and the reaction follows pseudo-first order kinetics. Cl^‒ accelerated the degradation of AY-17, but simultaneously led to an undesirable increase of absorbable organic halogen (AOX). Several chlorinated byproducts were identified by liquid chromatography-mass spectrometry (LC–MS/MS) in the UV/PDS system. It indicates that endogenic chlorine and exogenic Cl^– reacted with SO₄⁻ to form chloride radicals, which are involved in the dechlorination and rechlorination of AY-17 and intermediates. The possible degradation mechanisms of AY-17 photooxidative degradation are proposed. This work provides valuable information for further studies on the role of exogenic chloride in the degradation of chlorinated azo dyes and the kinetic parameters in the PDS-based oxidation process.     

Cross-talk Between (Hydrogen)Sulfite and Metalloproteins: Impact on Human Health

Sulfite is a potent toxic substance causing harm to multi-organ in human. Despite toxicity, it is widely used as preservative, anti-browning and anti-oxidant in foods, beverages, and pharmaceuticals, which cause easy admission of sulfite in human. Sulfite is also produced endogenously during the catabolism of cysteine and methionine. In vivo, the serum sulfite level at physiological range is strictly maintained by a molybdenum dependent sulfite oxidase (SO), which catalyzes sulfite to sulfate oxidation via a two-electron oxidation pathway. The loss of SO activity causes high serum sulfite level that fosters several diseases, including asthma, neurological dysfunction, birth defects, and heart diseases. The cytotoxicity of (bi)sulfite is implicated as sulfite radicals, which are generated by mainly heme-peroxidases via a one-electron oxidation pathway. On the other hand, the toxic sulfite radicals are neutralized to sulfite by heme-globins. The enzymatic reduction of sulfite to sulfide is catalyzed by sulfite reductase, which contains an unusual metal cofactor, siroheme-[4Fe4S]-cluster. Overall, the interaction of sulfite with various metalloproteins in vivo is a close relation with human health. Therefore, this review describes the metabolic conversion of (bi)sulfite to sulfate, sulfite radical or sulfide via oxidation or reduction pathways by various metalloproteins (specially SOs, peroxidases, heme-globins, and sulfite reductases), and the potential applications of sulfite in biosensors/biofuel cells, anti-browning, and advance oxidation process.     

A study on the free-radical evolution and its correlation with the optical degradation of 170 keV proton-irradiated polyimide

In this paper, the damage process was investigated on the 170 keV proton-irradiated polyimide, based on the evolution of free radical and its correlation with degradation of the optical transmittance using electron paramagnetic resonance (EPR) and optical-transmittance measurements. The results indicate that the g value of irradiated free radicals keeps at a constant of 2.0025 but the spectral intensity of the free radicals increased with the increasing proton fluence. It is found that during the post-storage after irradiation, the concentration of free radical decreased in an exponential rule with the post-storage time and the free-radical stability can be defined by the corresponding time constant at around 2.3 h. It is interested that the recovery of optical-transmittance follows the same mode as that of free radicals. The mechanisms on the free-radical evolution and the correlation between free radical and optical property are discussed in the paper.     

Application of Catalytic Wet Air Oxidation to Treatment of Landfill Leachate on Co／Bi Catalyst

Catalytic wet air oxidation(CWAO) was employed to reduce the organic compounds in landfill leachate and the effects of temperature, oxygen pressure, catalyst dosage, and concentration of the organic compounds on the TOC and CODcr removal rates were studied. The degradation kinetics of landfill leachate was also investigated and an exponential experiential model consisting of four influential factors was established to describe the reduction of the organic compounds in the landfill leachate. Meanwhile, the GC-MS technique was used to detect the components of the organic intermediates for the inference of the decomposition mechanisms of the organic compounds in landfill leachate. The results reveal that the reaction temperature and the catalyst dosage are the most important factors affecting the degradation reaction of the organic compounds and that the principal intermediates confirmed by GC-MS are organic acids at a percentage of more than 88% with no aldehydes or alcohols detected. The decomposition mechanisms of the organic compounds in landfill leachate were inferred based on the GC-MS information as follows;the activated gas phase O2 captured the hydrogen of the organic pollutants to produce free radicals, which then initiated the catalytic reaction. So most of the organic compounds were oxidized into CO2 and H2O ultimately. In general, catalytic wet air oxidation over catalyst Co3O4/Bi2O3 was a very promising technique for the treatment of landfill leachate.     

过硫酸盐活化高级氧化新技术

过硫酸盐在热、光、过渡金属催化等条件激活下产生强氧化性的硫酸根自由基·SO₄^-。基于·SO₄^-的过硫酸盐活化“高级氧化技术”在环境污染治理领域的应用,是刚刚发展起来的崭新的研究方向,具有广阔的应用前景。本文在分析其基本原理的基础上,综述了过硫酸盐活化技术在国内外土壤地下水有机污染原位修复、难降解有机废水处理等环境污染治理方面的研究进展,并就存在问题进行了研究展望。     

Radiation-induced oxidation of solid poly(ethylene oxide). II. Mechanism

The mechanism of γ-initiated oxidation of solid poly(ethylene oxide) (PEO) has been investigated, and an overall reaction scheme has been developed which accounts for most of the experimental observations. Data are correlated on the basis that the oxidation process is the sum of two reactions that are first-order and half-order in rate of initiation. They provide evidence that a significant fraction of the interactions of α-alkoxyalkylperoxy radicals is nonterminating at ambient temperature and yield free alkoxy radicals that are very subject to β scission. The unimolecular decomposition of secondary peroxy radicals, which has been invoked previously for the oxidation of PEO in solution, is not needed to explain the products of the oxidation of PEO in the solid phase. Approximately 90% of the total oxygen consumption has been accounted for by the observed products of oxidation. The radiochemical yield for backbone radical formation in irradiated PEO was estimated to be 6.5 ± 1.5.