天水大气降尘矿物与水作用产生羟基自由基研究

利用高效液相色谱法测定了甘肃天水市麦积镇降尘与水作用产生羟基自由基(·OH)的能力,并根据降尘中主要矿物的百分含量对降尘与水作用产生·OH进行理论和混合模拟.结果表明,天水降尘中的主要矿物组成为石英,方解石,钠长石,白云母.降尘及组成矿物成分与模拟降尘与水作用产生·OH能力大小顺序为:方解石(1.30×10^-10 mol)>理论模拟降尘(5.47×10^-11 mol)>降尘(5.34×10^-11 mol)>石英(2.90×10^-11 mol)>白云母(1.90×10^-11 mol)>钠长石(1.09×10^-11 mol)>混合模拟降尘(7.16×10^-12 mol).降尘中的矿物成分是降尘与水作用产生·OH的主要贡献者.降尘中矿物的组成和在水溶液中金属离子与有机物的溶出,降尘与水作用时的接触表面积,矿物组分之间水溶液中的相互作用,可能是导致降尘,混合模拟降尘,理论模拟降尘三者与水作用产生·OH量有所差异的原因.     

Mechanism and rate constants for complete series reactions of 19 fluorophenols with atomic H

Fluorine-containing halogenated fluorophenol may have efect as intermediate species involved in the formation of polyfluorinated dibenzo-p-dioxin/dibenzofurans(PFDDs/Fs). The mechanism for the atomic H initiated reactions with complete series of nineteen fluorophenol congeners was studies using the density functional theory. At the MPWB1K/6-31+G(d,p) level, the geometries and frequencies of reactants, transition states, and products were obtained, and the accurate energetic values were acquired at the MPWB1K/6-311+G(3df,2p) level. The rate constants were evaluated by the canonical variational transition-state theory with the small curvature tunneling contribution over a wide temperature range of 600–1000 K. The study shows that the intramolecular hydrogen-bond in the ortho-substituted FPs as well as the inductive efect of the electron-withdrawing fluorine and steric repulsion of multiple substitutions may ultimately be responsible for the relative strength of the O–H bonds in FPs. The results can be used for further studies on PFDD/Fs formation mechanism.     

Fe_3O_4/石墨烯活化过硫酸盐降解罗丹明B废水的研究

利用水热法合成石墨烯负载Fe3O4催化剂,利用X-射线衍射、红外光谱、比表面积等对其进行表征。以Fe3O4/石墨烯为催化剂,活化过硫酸钾降解罗丹明B,考察了石墨烯与Fe3O4配比、催化剂用量、氧化剂浓度、pH值和温度等因素对其降解性能的影响。石墨烯的加入可以显著提高罗丹明B的降解率,氧化剂用量的增加有利于降解反应,弱酸性条件有利于降解;温度升高对罗丹明B降解有利。在该反应体系中存在的自由基以SO-4为主,·OH和O-2为辅。     

超声、紫外增强H2O2/KI降解磺胺甲基嘧啶

实验以H_2O_2和KI作为分子碘(I2)的来源,研究比较了超声、紫外分别增强H_2O_2/KI降解磺胺甲基嘧啶(sulfamerazine,SMR)的效果、主要影响因素、分子碘的生成、主要活性物种和产物.结果表明,超声、紫外均能有效增强H_2O_2/KI对磺胺甲基嘧啶的降解,超声的增强效果明显;pH值对磺胺甲基嘧啶的去除率影响较大,pH为2.6~5.6,去除率随pH升高而降低;自由基抑制结果表明,碘自由基(I·和I-2·)是超声、紫外增强H_2O_2/KI降解磺胺甲基嘧啶的主要活性物质.HPLC/MS/MS分析检测到一碘代苯.     

三维有序介孔Co3O4非均相活化单过硫酸氢钾降解罗丹明B

以多孔硅KIT-6为模板,采用纳米浇筑法制备三维有序介孔Co_3O_4,利用比表面积测试仪(BET)、高倍投射电子显微镜(H-TEM)、X射线衍射光谱(XRD)、X射线光电子能谱(XPS)、傅里叶变换红外光谱(FT-IR)等方法进行表征,并首次将其应用于催化单过硫酸盐降解罗丹明B.结果表明,三维有序介孔Co_3O_4具有丰富的空间介孔结构和巨大的比表面积,对单过硫酸盐的催化活性远强于传统纳米级Co_3O_4.较高的催化剂投加量和较高的单过硫酸盐浓度有利于罗丹明B的脱色.在反应体系中出现Cl-和H2PO-4能够加速罗丹明B的脱色,而出现NO_3~-、SO_4~(2-)和HCO_3~-则会抑制罗丹明B的去除.通过自由基鉴定实验发现,硫酸自由基是导致罗丹明B脱色的主导活性自由基.三维有序介孔Co_3O_4经过多次重复使用后仍表现出良好的催化活性.     

UV-vis光照下唑类抗菌药氟康唑的光化学反应类型

以唑类抗菌药氟康唑为模型化合物,考察了其在纯水中的光降解动力学和光化学反应类型,发现模拟日光(λ>290nm)照射下氟康唑未发生光解,在UV-vis(λ>200 nm)光照下,氟康唑发生了光降解并服从准一级反应动力学.采用活性氧物种猝灭实验和竞争动力学方法,研究发现氟康唑发生了直接光解和·OH参与的自敏化光解,氟康唑与.OH的反应速率常数为(5.95±0.58)×109L·(mol·s)-1,表层水体中相应的半减期为(32.41±3.16)h·通过鉴定光解产物,得知氟康唑发生了脱氟、光致水解、光氧化等光化学反应.     

Determination of photochemically-generated reactive oxygen species (ROS) in natural water

Reactive oxygen species (ROS) can be produced by interactions between sunlight and light-absorbing substances in natural water environment. ROS may participate in the indirect photolysis of trace organic pollutants, therefore resulting in the changing of their environmental fates and ecological risks in natural water system. Bisphenol A (BPA), an endocrine-disrupting chemical, exits widely in natural water. The photodegradation of BPA promoted by ROS (·OH, 1O2, HO2·/O2·-) which were produced on the excitation of ubiquitous constituents (such as nitrate ion, humic substances and Fe(III)-oxalate complexes) in natural water under simulated solar radiation was investigated. Both molecular probe method and electron spin resonance (ESR) test were used for the determine the characterization of generated ROS. It was found that ·OH was photochemically produced with the presence of nitrate ion, humic substances and Fe(III)-oxalate complexes and 1O2 was produced with the presence of humic substances. The steady-state concentrations of ·OH was 1.27×10-14 mol/L in nitrate ion, and the second-order rate constant of BPA with ·OH was 1.01×1010L/( mol·s).     

Determination of photochemically-generated reactive oxygen species in natural water

Reactive oxygen species(ROS) can be produced by interactions between sunlight and light-absorbing substances in natural water environment.ROS may participate in the indirect photolysis of trace organic pollutants,therefore resulting in changes in their environmental fates and ecological risks in natural water systems.Bisphenol A(BPA),an endocrine-disrupting chemical,exits widely in natural waters.The photodegradation of BPA promoted by ROS(.OH,1O2,HO2./O2·-),which were produced on the excitation of ubiquito...     

无机阴离子对CuO-H2O2氧化苯酚废水的影响

以苯酚为模型底物,研究了中性低温常压条件下无机阴离子对CuO-H₂O₂氧化苯酚废水的影响及机制.结果表明,CuO-H₂O₂能高效彻底氧化苯酚,10 min氧化率达94.7%,氧化遵循羟基自由基机制.无机阴离子对氧化效果有不同影响,浓度越高影响越显著.HCO^-₃加速H₂O₂的无效分解,当浓度从0增加到20 mmol·L^-1 时,H₂O₂分解速率常数由0.373 8 min^-1提高到0.534 7 min^-1,TOC去除速率常数由0.267 min^-1下降到0.019 4 min^-1.HPO^2-₄通过抑制H₂O₂分解实现对苯酚的氧化抑制,H₂O₂分解速率常数及TOC去除速率常数分别由0.373 8 min^-1、0.267 min^-1降低到0.033 8 min^-1、 0.033 8 min^-1.Cl^-能够促进H₂O₂有效分解,对苯酚氧化有利,H₂O₂分解速率常数及TOC去除速率常数分别由0.373 8 min^-1、0.267 min^-1提高到0.604 0 min^-1、0.387 9 min^-1.NO^-₃、SO^2-₄对H₂O₂的分解及苯酚的氧化影响不大.     

水体系中EDTA-Fe(Ⅱ)/Ｋ２Ｓ２Ｏ８降解敌草隆的研究

对水体系中EDTA-Fe(Ⅱ)/K2S2O8降解敌草隆的方法进行了研究.在综合考虑经济性和降解率的前提下,提出了反应的最佳条件:K2S2O8初始浓度为2.0 mmol·L-1, Fe(Ⅱ)初始浓度为1.0 mmol·L-1, EDTA初始浓度为0.5 mmol·L-1,反应时间为300 min, pH=7.0,最终0.1 mmol·L-1,敌草隆降解率可达67.6%.同时,采用分子探针竞争实验鉴定了体系中产生的硫酸根自由基和羟基自由基,并采用LC/MS法鉴定了敌草隆的主要降解产物,从而探讨了敌草隆在EDTA-Fe(Ⅱ)/K2S2O8体系中可能的降解途径.