UV/NO3-光化学降解水中的磺胺甲恶唑

本文研究了UV/NO₃^-体系对水中磺胺甲恶唑（SMX）的降解;考察了NO₃^-用量、pH值、SMX初始浓度、水体成分中常见的无机阴离子（Cl^-、SO₄^2-和HCO₃^-）和天然有机物（NOM）对SMX去除的影响;最后探讨了SMX在该体系中的降解产物和转化机理.结果表明：相比于单独UV,UV/NO₃^-对SMX的去除效果更优,这可能归因于UV激发NO₃^-产生的羟基自由基（HO^·）,通过加入HO^·淬灭剂甲醇,有力地证明了体系中HO^·的存在及其对SMX的降解作用.SMX在UV/NO₃^-体系中的降解符合准一级反应动力学.SMX的去除效率随着NO₃^-浓度的增加而逐渐提高,随着其初始浓度的增大而减小.溶液pH值对UV/NO₃^-降解SMX的影响显著,SMX去除效率表现为酸性>中性>碱性.向UV/NO₃^-体系中加入不同浓度的Cl^-和SO₄^2-对SMX的降解基本没有影响;HCO₃^-对SMX的去除有显著的促进作用,这可能归因于HO^·同HCO₃^-反应产生的碳酸根自由基（CO₃^·-）;NOM的存在会抑制SMX的降解,且NOM浓度越高,抑制越明显.在UV/NO₃^-降解SMX的反应中,根据检出的5种产物,提出SMX可能的转化机理包括4种不同的反应路径,分别为断键反应、脱氨羟基化、羟基化和亚硝化.     

零价铁活化过硫酸钠降解2-萘磺酸

近几年来,基于SO-4·的新型高级氧化技术逐渐成为水处理领域的研究热点。利用零价铁活化过硫酸钠产生SO-4·对水溶液中2-萘磺酸开展了降解研究。考察了零价铁投加量、过硫酸钠浓度、温度、p H值、腐殖酸、富里酸、硫酸盐及2-萘磺酸初始浓度对2-萘磺酸降解效果的影响。结果表明:温度升高,酸性或中性环境下有利于2-萘磺酸的降解;零价铁投加量为0.1 g/L、过硫酸钠浓度为3.0 mmol/L时,2-萘磺酸的降解率高达96.8%;腐殖酸和富里酸的存在有利于2-萘磺酸降解,硫酸钠的存在会抑制2-萘磺酸降解。研究表明:采用零价铁活化过硫酸盐降解技术去除水溶液中2-萘磺酸具有广阔的应用前景。     

雌二醇在铁(Ⅲ)-草酸盐配合物体系中的光降解

以125W高压汞灯为光源,研究了水中雌二醇(E2)在铁(Ⅲ)-草酸盐体系中的光降解;考查了初始pH值、铁(Ⅲ)/草酸盐配比、E2初始浓度对E2光降解的影响.结果表明,铁(Ⅲ)/草酸盐体系能引发E2光降解.在pH=3·50,Fe(Ⅲ)/草酸盐配比为10·0/120·0μmol·l-1时,2mg·l-1E2光照160min可降解48·0%.在pH3·0—6·0范围内,pH值为3·0—4·0时E2降解率较高;在2·0—10·0mg·l-1范围内,光降解效率随水溶液中E2初始浓度的增加而降低.     

水体中苯与亚硝酸的紫外光解交叉反应机理研究

利用激光闪光光解技术对不同条件下苯与亚硝酸水溶液的交叉反应机理进行研究,考察了瞬态物种的生长与衰减等行为;得到了C6H6-OH加合物,C6H6-NO^ π络合物等中间产物,并结合其光解产物的GC／MS分析,对其可能的反应机理进行了探讨,得出了一些微观反应速率常数．     

水相中CCl4和CHCl3的紫外光解机理

利用瞬态吸收光谱技术研究水体污染物CCl₄和CHCl₃在紫外光照条件下的转化和归宿,表明在248nm激光作用下,CCl₄解离为CCl₃和Cl自由基;CHCl₃在此条件下不解离,但加入少量的苯后即发生明显解离,产生CHCl₂和Cl自由基.在有氧条件下,光解产生的CCl₃和CHCl₂自由基均与O₂反应分别生成CCl₃O₂和CHCl₂O₂;在无氧条件下,CCl₃和CHCl₂则发生偶合反应分别生成C₂Cl₆和C₂H₂Cl₄.本研究还得出了一些微观速率常数.     

Treatment of two insecticides in an electrochemical Fenton system

Abstract

The ability of an electrochemical Fenton system to degrade the organophosphorous insecticides malathion and methyl parathion was studied. A combination of hydrogen peroxide and electrochemically‐generated iron was found to be successful in degrading the two insecticides, and optimization of the system was pursued. Augmentation with near UV light at an intensity of 1.67xl0¹⁷ quanta/sec and centered at a wavelength of 370 nm improved the degradation of malathion at low iron concentrations but did not affect other treatments. Adding the hydrogen peroxide slowly over the course of treatment rather than all at once at the beginning of each treatment did, however, greatly improve the system. Removal efficiencies of 98.0% or greater were achieved for both pesticides.     

Toward better understanding vacuum ultraviolet–iodide induced photolysis via hydrogen peroxide formation,iodine species change,and difluoroacetic acid degradation

• UV/VUV/I^– induces substantial H₂O₂ and IO₃^– formation, but UV/I^– does not. • Increasing DO level in water enhances H₂O₂ and iodate productions. • Increasing pH decreases H₂O₂ and iodate formation and also photo-oxidation. • The redox potentials of UV/VUV/I^– and UV/VUV changes with pH changes. • The treatability of the UV/VUV/I^– process was stronger than UV/VUV at pH 11.0. Recently, a photochemical process induced by ultraviolet (UV), vacuum UV (VUV), and iodide (I^–) has gained attention for its robust potential for contaminant degradation. However, the mechanisms behind this process remain unclear because both oxidizing and reducing reactants are likely generated. To better understand this process, this study examined the evolutions of hydrogen peroxide (H₂O₂) and iodine species (i.e., iodide, iodate, and triiodide) during the UV/VUV/I^– process under varying pH and dissolved oxygen (DO) conditions. Results show that increasing DO in water enhanced H₂O₂ and iodate production, suggesting that high DO favors the formation of oxidizing species. In contrast, increasing pH (from 6.0 to 11.0) resulted in lower H₂O₂ and iodate formation, indicating that there was a decrease of oxidative capacity for the UV/VUV/I^– process. In addition, difluoroacetic acid (DFAA) was used as an exemplar contaminant to verify above observations. Although its degradation kinetics did not follow a constant trend as pH increases, the relative importance of mineralization appeared declining, suggesting that there was a redox transition from an oxidizing environment to a reducing environment as pH rises. The treatability of the UV/VUV/I^– process was stronger than UV/VUV under pH of 11.0, while UV/VUV process presented a better performance at pH lower than 11.0.     

Nafion膜中嵌入Fe~(2+)光催化降解亚甲基蓝的研究

将亚铁离子嵌入Nafion膜中利用Fe3+/Fe2+光催化降解亚甲基蓝,脱色率达90%。研究探讨了降解亚甲基蓝时H 2O2以及pH值的影响。亚甲基蓝光催化降解氧化反应符合一级动力学规律,表观速率常数为0.5689min-1。     

三维固定床电极法降解焦化废水

采用三维电极固定床技术对焦化废水进行了深度处理的实验研究,并取得了相应的工艺参数。实验研究结果表明,三维电极技术能有效的处理焦化废水,在槽电压为12V,液体催化剂量为1500mg/L,反应时间为60min,pH为3,COD去除率可达62%。     

Activation of sulfite by metal-organic framework-derived cobalt nanoparticles for organic pollutants removal

Sulfite (SO₃²⁻) activation is one of the most potential sulfate-radical-based advanced oxidation processes, and the catalysts with high efficiency and low-cost are greatly desired. In this study, the cobalt nanoparticles embedded in nitrogen-doped graphite layers (Co@NC), were used to activate SO₃²⁻ for removal of Methyl Orange in aqueous solution. The Co@NC catalysts were synthesized via pyrolysis of Co²⁺-based metal-organic framework (Co-MOF), where CoO was firstly formed at 400℃ and then partially reduced to Co nanoparticles embedded in carbon layers at 800℃. The Co@NC catalysts were more active than other cobalt-based catalysts such as Co²⁺, Co₃O₄ and CoFe₂O₄, due to the synergistic effect of metallic Co and Co_xO_y. A series of chain reaction between Co species and dissolved oxygen was established, with the production and transformation of SO₃^•−, SO₅²⁻, and subsequent active radicals SO₄^•− and HO•. In addition, HCO₃⁻ was found to play a key role in the reaction by complexing with Co species on the surface of the catalysts. The results provide a new promising strategy by using the Co@NC catalyst for SO₃²⁻ oxidation to promote organic pollutants degradation.