晶面协同TiO2的制备及其可见光催化特性

以不同氟化物为晶面控制剂,采用超声辅助-溶胶凝胶法制备｛001｝和｛101｝晶面协同的F-TiO₂,借助XRD、TEM和EDS表征其物相结构、微观形貌和元素组成,通过改变氟化物种类和添加量确定F-TiO₂的最佳制备条件,并探讨其可见光催化过程中的主要活性物种及作用机理,研究关键反应参数对F-TiO₂光催化活性的影响.结果表明,引入NH₄F、NaF和HF可调控TiO₂沿｛001｝、｛101｝晶面生长,同时F^-掺杂能够增大材料的比表面积,制备所得材料的光催化性能均高于纯TiO₂.但在NaBF₄调控下合成的TiO₂为锐钛矿/金红石/Na₃TiF₆三相共存的半导体耦合结构,可见光催化活性显著下降.当NH₄F添加量为0.1 g时,材料显示出最强的光催化性能,可见光照射60 min后RhB的降解率为97.24%,矿化率达78.39%.降解反应符合一级反应动力学规律,速率常数为0.1321 min^-1.通过自由基捕获实验和ESR测试发现,h⁺、·OH均以关键活性因子参与F-TiO₂的可见光催化过程.F-TiO₂光催化活性增强主要归因于｛001｝和｛101｝晶面的协同作用和表面异质结的形成,其能有效提高光催化反应过程中光生电子空穴对的分离和迁移效率.在可见光照射下,适当增加催化剂投加量,降低RhB初始浓度,控制溶液为中性环境,可显著提高材料的降解速率.     

·OH自由基介导2,4-二氯酚光降解机理及产物毒性变化特征的理论研究

由于2,4-二氯酚(2,4-dichlorophenol,简称2,4-DCP)具有"三致"作用及潜在的生态风险,其光化学降解机理及产物的生态毒理效应目前成为人们关注的焦点。本研究采用理论化学计算手段,系统阐明了2,4-DCP在水环境中·OH介导的间接光化学转化机理、动力学和转化产物的生态毒性变化特征。结果表明2,4-DCP很容易被·OH氧化降解,其降解主要通过·OH-加成和H-迁移路径进行。在低温条件下·OH-加成路径将占主导,主要形成4,6-二氯苯-1,3-二酚;而当温度超过313 K时,·OH提取酚羟基上的氢原子为主要降解途径,主要形成2-氯苯-对苯醌。尤其在活性物种浓度较低的高温环境中,H-迁移路径有可能生成二噁英。计算毒理学结果表明:H-迁移产物的水生毒性超过·OH-加成产物,甚至超出母体2,4-DCP一个毒性等级。因此,我们建议在以后的环境监测以及风险评估过程中,关注2,4-DCP及其转化产物特别是H-迁移路径的转化产物的生态毒理学问题。     

Nitro polycyclic aromatic hydrocarbons in atmospheric particulate matter of Athens,Greece

Polycyclic aromatic hydrocarbons (PAHs) and nitro polycyclic aromatic hydrocarbons (N-PAHs) are chemical species of proven mutant and carcinogenic activity. In this study, the concentrations of seven different N-PAHs [2-nitronaphthalene (2N-NAP), 2-nitroflourene (2N-FLU), 2-nitroflouranthene (2N-FLA), 3-nitroflouranthene (3N-FLA), 1-nitropyrene (1N-PYR) and 2-nitropyrene (2N-PYR)] were determined in two fractions of atmospheric particulate matter from the atmosphere of Athens: coarse (2.4 μm?10 μm ) and fine (<2.4 μm ). 3N-FLA was not detected, whereas 1N-PYR, mostly originating from emissions from burning fuel, showed the maximum observed concentrations for both fractions and for the whole experimental period (especially during winter). In addition, 2N-FLA, a secondary nitro-PAH produced by photochemical reactions, showed relatively high values. Analysis of statistical data for N-PAH concentrations, using clustering technique, showed that: (1) 1N-NAP, 2N-FLU and 1N-PYR are mainly produced by direct burning; and (2) photochemical reactions are the dominant sources of 2N-NAP, 2N-PYR and 2N-FLA.     

Photo- and electro-catalysis for solar disinfection of Escherichia coli-contaminated water using Ag–TiO2/graphite

A titanium dioxide film on a graphite substrate was synthesized by chemical bath deposition from TiCl₄ as precursor and with the surfactant cetyl trimethyl ammonium bromide as a linking and assembling agent. Silver was loaded on the TiO₂ film by electrodeposition at 0.025?A. Water contaminated with Escherichia coli was disinfected under sunlight irradiation by photolysis (Lys), photocatalysis (PC), photoelectrocatalysis (PEC), and electrocatalysis (EC). The highest rate constant, k, was achieved with EC; k was 5.1?×?10^?2 colony forming units (CFU) mL^?1?min^?1. However, auto-oxidation of Ag occurred during EC and PEC. Meanwhile, the rate constant of disinfection by means of PC was lower than EC and PEC, and k was 3.82?×?10^?2 CFU?mL^?1?min^?1. Nevertheless, the auto-oxidation of Ag in the Ag–TiO₂/graphite tablet did not occur during the disinfection process.     

Behavior of aqueous stable colloidal nano-C60 aggregates exposed to TX100 micelles under different environmental conditions

C₆₀, as one of carbon nanomaterials widely used in various fields, could be released into the water environment thus exerting some potential health risks to human beings. This work examined the behavior of aqueous stable colloidal nano-C₆₀ (nC₆₀) aggregates under different environmental conditions including Polyethylene glycol octylphenol ether (TX100) micelles concentration, pH, and reaction time when exposed to TX100 micelles. Results show that the nC₆₀ aggregates became more dispersive and restored the capability of generating the singlet oxygen when exposed to TX100 micelles. With the increase of TX100 concentration, smaller average size of nC₆₀ aggregates was observed in dynamic light scattering (DLS) analysis, the fluorescence intensity of TX100 was more quenched by nC₆₀ aggregates, and the kinetic rate constant of generating the singlet oxygen for nC₆₀ aggregates was improved. The mean size of nC₆₀ aggregates in the presence of TX100 had no obvious variations when the pH ranged from 4 to 8. The longer reaction time between nC₆₀ aggregates and TX100 led to a higher kinetic rate constant of generating the singlet oxygen. Collective data suggest that variations in physicochemical properties of nC₆₀ aggregates are strongly dependent on the surrounding media under different environmental conditions and directly govern nC₆₀’s transport behavior and potential toxicity.     

Al(III)对糖浆溶液中有机还原物质还原六价铬的影响

通过批实验研究了Al(III)对糖浆溶液化学还原六价铬反应的影响,揭示了不同条件下Al(III)对六价铬还原反应动力学的影响.结果表明:Al(III)能够促进糖浆溶液还原六价铬反应进行;其作用机制是Al(III)与糖浆溶液中有机还原物质及Cr(VI)反应形成三者的络合物,降低糖浆中多酚等有机还原物质还原Cr(VI)的反应活化能,提高六价铬还原反应速率.Al(III)存在时,该六价铬还原反应符合准一级动力学反应; pH 2.0,2.5,3.0,3.5时,添加Al(III)的实验组中六价铬反应速率常数比对应的空白对照组中反应速率常数分别增加了0.0251,0.0139,0.0058, 0.0048h-1.添加Al(III)前后反应体系中六价铬还原的反应活化能(Eа)分别为66.38,62.80kJ/mol.当糖浆浓度不足时,Al(III)能够提高糖浆溶液还原六价铬的反应去除率.     

Enzymatic nitrous oxide emissions from wastewater treatment

Nitrous oxide (N₂O), a potent greenhouse gas, is emitted during nitrogen removal in wastewater treatment, significantly contributing to greenhouse effect. Nitrogen removal generally involves nitrification and denitrification catalyzed by specific enzymes. N₂O production and consumption vary considerably in response to specific enzyme-catalyzed nitrogen imbalances, but the mechanisms are not yet completely understood. Studying the regulation of related enzymes’ activity is essential to minimize N₂O emissions during wastewater treatment. This paper aims to review the poorly understood related enzymes that most commonly involved in producing and consuming N₂O in terms of their nature, structure and catalytic mechanisms. The pathways of N₂O emission during wastewater treatment are briefly introduced. The key environmental factors influencing N₂O emission through regulatory enzymes are summarized and the enzyme-based mechanisms are revealed. Several enzymebased techniques for mitigating N₂O emissions directly or indirectly are proposed. Finally, areas for further research on N₂O release during wastewater treatment are discussed.

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成都郊区(新津)夏季甲醛污染特征分析

甲醛（HCHO）是大气光化学重要污染物之一,为研究西南地区郊区大气夏季甲醛污染特征选取了四川省成都市新津区进行大气甲醛观测,结合NO_x、O₃、PAN、J-value、温湿度、风速风向、天气数据进行分析.观测期间成都市新津区夏季甲醛浓度为0.76×10^-9~12.50×10^-9（V/V）,均值为3.47×10^-9±2.05×10^-9（V/V）,呈现明显的日变化规律.结合数据分析可知,一次人为排放源在成都郊区夏季日间甲醛贡献中占比较低.观测期间甲醛受光照的影响较大,与O₃、PAN、J-value普遍呈现一致的变化规律,因此成都市夏季日间甲醛主要来源为甲醛前体物的二次光化学反应.     

电解氢氧化钠水溶液处理十二碳硫醇恶臭污水

采用电解NaOH水溶液配合活性炭催化氧化法来处理十二碳硫醇恶臭污水,并进行了初步的实验研究,取得了良好的效果。实验用的直流电解槽以石墨作为阳极,有效面积为30cm^2;不锈钢作为阴极,有效面积为9cm^2,并保持两极极板距离20mm。实验结果表明,在电流3A条件下电解质量分数为1％的NaOH水溶液,以活性炭作催化剂,反应温度为20℃,反应时间10～30s可以去除十二碳硫醇恶臭物质。处理后的污水无色无臭,可以直接排放。     

基于碳同位素组成的大气NMHCs光化学寿命研究

利用热解析-气相色谱-同位素质谱联用仪测定了兰州市冬季和夏季昼夜大气非甲烷烃(NMHCs)的稳定碳同位素组成.结果表明,兰州市冬季大气NMHCs的δ13C值为-30.5‰～-24.3‰,夏季为-31.9‰～-24.2%,受燃煤烟气排放的影响,冬季大气NMHCs的δ13C值明显大于夏季;冬季大气NMHCs的δ13C值夜晚大于白天,夏季不同时间点C4、C5化合物的同位素值相差不大,正己烷和正庚烷的δ13C值白天比夜晚要高.利用"碳氢化合物同位素时钟"计算出正己烷和1-丁烯在兰州市夏季大气中的平均光化学寿命分别约为6d和25min.