Intrinsic chemiluminescence production from the degradation of haloaromatic pollutants during environmentally-friendly advanced oxidation processes: Mechanism, structure–activity relationship and potential applications

The ubiquitous distribution of halogenated aromatic compounds(XAr) coupled with their carcinogenicity has raised public concerns on their potential risks to both human health and the ecosystem. Recently, advanced oxidation processes(AOPs) have been considered as an"environmentally-friendly" technology for the remediation and destruction of such recalcitrant and highly toxic XAr. During our study on the mechanism of metal-independent production of hydroxyl radicals(UOH) by halogenated quinones and H_2O_2, we found, unexpectedly, that an unprecedented UOH-dependent two-step intrinsic chemiluminescene(CL) can be produced by H_2O_2 and tetrachloro-p-benzoquinone, the major carcinogenic metabolite of the widely used wood preservative pentachlorophenol. Further investigations showed that, in all UOH-generating systems, CL can also be produced not only by pentachlorophenol and all other halogenated phenols, but also by all XAr tested. A systematic structure–activity relationship study for all 19 chlorophenolic congeners showed that the CL increased with an increasing number of Cl-substitution in general. More importantly, a relatively good correlation was observed between the formation of quinoid/semiquinone radical intermediates and CL generation. Based on these results, we propose that UOH-dependent formation of quinoid intermediates and electronically excited carbonyl species is responsible for this unusual CL production; and a rapid, sensitive,simple, and effective CL method was developed not only to detect and quantify trace amount of XAr, but also to provide useful information for predicting the toxicity or monitoring real-time degradation kinetics of XAr. These findings may have broad chemical, environmental and biological implications for future studies on halogenated aromatic persistent organic pollutants.     

生物淋滤联合类Fenton反应去除污染土壤中重金属的效果

针对我国南方地区广泛存在的土壤重金属污染问题,以广东韶关铅锌矿周边污染农田土壤为研究对象,探讨利用生物淋滤方法与生物淋滤联合类Fenton反应对土壤Cu、Zn、Cd和Pb的去除效果,并采用序列化学提取(SEC)方法,分析不同处理对土壤中4种重金属形态分布的影响.结果表明,经12 d生物淋滤Cu、Zn、Cd和Pb的去除率分别达到66.5%、55.1%、72.8%和35.6%,其中无机结合态重金属去除效果最好,固相中剩余重金属主要以稳定的残渣态形式存在.2 d生物淋滤联合类Fenton反应在优化的H_2O_2浓度(5 g·L-1)下,对上述4种重金属的去除率分别为55.6%、50.6%、60.7%和30.5%,低于12 d生物淋滤处理,但显著高于H_2SO_4酸化、2 d生物淋滤、化学Fenton反应等对照处理.生物淋滤联合类Fenton反应可以实现原土壤中残渣态、有机结合态和无机结合态等较稳定态重金属的有效去除,使处理后土壤中4种重金属Cu、Zn、Cd和Pb的含量分别低于50、200、0.3和250 mg·kg~(-1)的标准限值.该方法兼具生物淋滤高去除效率和Fenton反应快速处理等优势,对于修复重金属Cu、Zn、Cd和Pb等复合污染的土壤具应用前景.     

Heterogeneous reaction of SO2 on CaCO3 particles: Different impacts of NO2 and acetic acid on the sulfite and sulfate formation

Despite the heterogeneous reaction of sulfur dioxide (SO₂) on mineral dust particles significantly affects the atmospheric environment, the effect of acidic gases on the formation of sulfite and sulfate from this reaction is not particularly clear. In this work, using the in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) technique, we employed a mineral dust particle model (CaCO₃) combined with NO₂ and acetic acid to investigate their effects on the heterogeneous reaction of SO₂ on CaCO₃ particles. It was found that water vapor can promote the formation of sulfite and simulated radiation can facilitate the oxidation of sulfite to sulfate. The addition of NO₂ or acetic acid to the reaction system altered the production of sulfate and sulfite accordingly. There was a synergistic effect between NO₂ and SO₂ that promoted the oxidation of sulfite to sulfate, and a competitive effect between acetic acid and SO₂ that inhibited the formation of sulfite. Moreover, light and water vapor can also affect the heterogeneous reaction of SO₂ with the coexistence of multiple gases. These findings improve our understanding of the effects of organic and inorganic gases and environmental factors on the formation of sulfite and sulfate in heterogeneous reactions.     

CL-20/HTPB热分解机理的ReaxFF/lg反应分子动力学模拟

目的 揭示CL-20和HTPB复合体系的热分解机理,同时为CL-20/HTPB复合推进剂配方设计与应用提供理论依据。方法 采用反应分子动力学方法(ReaxFF/lg),研究CL-20/HTPB混合体系在2 500~3 500 K中5个温度下的热分解机理。结果 混合体系中的CL-20分子间反应路径仍为脱硝基和开环等反应。HTPB为混合体系引入大量的H原子与OH基团,这些自由基会与CL-20及CL-20的分解产物发生反应,例如与HNO2的大量化学反应促进了CL-20的热分解。相比CL-20单质体系,混合体系下,HNO2生成反应数量均有不同程度的增加。通过与单组分产物数量的比较可以发现,H2O的含量大大增加,且曲线到达峰值的时间更短,体系分解反应速率更快,同时CO2的含量也大幅度地减少。除此之外,所计算的混合体系的活化能(Ea)与指前因子的自然对数lnA分别为114.684 kJ/mol与25.896。对比CL-20单质体系,混合体系的活化能较小。结论 HTPB会对CL-20的热分解起到促进的作用,降低了系统对热刺激的不敏感程度。     

气相色谱酯化反应的最佳条件

衍生化处理，对于气相色谱检验环境中的微量有机物有着重要的作用，酯化反应是最常用的方法，正越来越广泛地运用到多种酸性物质的衍生化处理中。根据酯化反应催化的原理，在实验中发现反应的最佳条件是：温度为80℃，选用硫酸氢钠或三氯化铁催化剂，催化剂用量为2g。     

NOx和VOC自然源排放及其对中国地区对流层光化学特性影响的数值模拟研究

利用Williams等和Guenther等的模型估计中国地区NO_x和VOC的自然源排放.所得清单显示土壤NO_x排放总量（以N计）为225.75 Gg;植被VOC年排放总量（以C计）为13.23 Tg,其中异戊二烯、单萜烯、其它VOC分别为7.77、1.86、3.60 Tg;排放有明显季节变化和空间变化.运用中尺度气象模式MM5以及光化学模式Calgrid研究这些排放在不同季节对对流层化学的影响.结果表明,O₃、NO_x、HNO₃和PAN的全国平均浓度在土壤NO_x排放影响下分别增加15.3%、15.7%、25.5%和6.5%;在植被VOC排放影响下改变5.6%、-4.9%、-19.3％和142.3％;在两者综合影响下增加26.1%、8.8%、4.3%和177.9%;浓度变化在夏季明显强于其它季节.自然源对中国地区光化学污染物空间分布有不同程度的影响,这种影响同区域气象条件、源排放和NMHC/NO_x比值等因素有关.NO_x和VOC的自然源排放对光化学特性影响显著,在光化学模拟过程中不容忽视.     

操作条件对污水再生处理絮凝工艺中病原性原虫去除特性的影响

再生水中的隐孢子虫和贾第鞭毛虫会通过直接或间接的方式影响人体健康.与传统的消毒手段相比,絮凝、澄清、过滤等污水深度处理工艺能有效地控制两虫污染.本研究主要考察了絮凝剂种类、投加量、pH和温度等操作条件对污水再生处理絮凝过程中病原性原虫去除特性的影响.结果发现,污水絮凝过程中,pH为6～8时两虫的去除率较高,低温条件不利于两虫的去除.氯化铁对两虫的去除率随投加量的增加而增加;硫酸铝絮凝和聚合氯化铝的最佳投加量分别为70 mg/L和20　mg/L左右.     

Heterogeneous reaction of NO2 on the surface of montmorillonite particles

The studies on heterogeneous reactions over montmorillonite, which is a typical 2:1 layered aluminosilicate, will benefit to the understanding of heterogeneous reactions on clay minerals. Montmorillonite can be classified as sodium montmorillonite or calcium montmorillonite depending on the cation presented between the different layers. Using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), the heterogeneous reaction mechanism of NO₂ on the surface of montmorillonite was firstly investigated. Results showed that the reaction of NO₂ on the surface of sodium and calcium montmorillonite fit a first-order kinetics, and the reaction duration of calcium montmorillonite was longer than that of sodium montmorillonite under the dry condition. For either sodium or calcium montmorillonite, the uptake coefficient decreased as humidity increased.     

零价铁降解4-氯硝基苯动力学研究

实验采用无氧条件下不同浓度零价铁降解硝基芳香烃代表物4-氯硝基苯,研究4-氯硝基苯的降解速率及各产物的反应速率.根据化学反应计量学,通过准一级动力学方程对实验结果进行拟合,得到生成各产物反应速率,并利用穆斯堡尔技术检测零价铁的产物.结果表明,4-氯硝基苯的还原转化速率与零价铁浓度有关,中间产物4-氯亚硝基苯和4-氯苯基羟胺的生成和转化速率可通过拟合各反应速率得到.当零价铁浓度为1.04 g.L-1时4-氯硝基苯反应速率最快,反应速率常数为0.189min-1.反应过程中生成的亚铁离子在反应初期吸附在零价铁表面,各物质的生成和还原速率取决于零价铁表面的活性位点和各物质与零价铁之间的质量传递.