Enhanced photodegradation of phenolic compounds by adding TiO2 to soil in a rotary reactor

Photodegradation ofpentachlorophenol （PCP） and p-nitrophenol （PNP） in soil was carried out in a designed rotary reactor, which can provide the soil particles with continually uniform irradiation, and on a series of thin soil layers. TiO2, as a kind of environmental friendly photocatalyst, was introduced to the soil to enhance the processes. Compared with that on the soil layers, photodegradation of PCP at initial concentration of 60 mg/kg was improved dramatically in the rotary reactor no matter whether TiO2 was added, with an increase of 3.0 times in the apparent first-order rate constants. The addition of 1 wt% TiO2 furthered the improvement by 1.4 times. Without addition of TiO2, PNP （initial concentration of 60 mg/kg） photodegradation rate in the rotary reactor was similar to that on the soil layers. When 1 wt% additional TiO2 was added, PNP photodegradation was enhanced obviously, and the enhancement in the rotary reactor was 2 times of that on the soil layers, which may be attributed to the higher frequency of the contact between PNP on soil particles and the photocatalyst. The effect of soil pH and initial concentrations of the target compounds on the photodegradation in the rotary reactor was investigated. The order of the degradation rate at different soil pH was relative to the aggregation of soil particles during mixing in the rotary reactor. Photodegradation of PCP and PNP at different initial concentrations showed that addition of TiO2 to enhance the photodegradation was more suitable for contaminated soil with higher concentration of PCP, while was effective for contaminated soil at each PNP concentration tested in our study.     

化工生产过程中活性危害识别

讨论了化工生产过程中活性危害的基本概念、识别方法和步骤,并以苯胺生产装置为例,利用文中提出的方法和程序进行活性危害识别.     

Nocturnal atmospheric chemistry of NO3 and N2O5 over Changzhou in the Yangtze River Delta in China

Comprehensive observations of the nocturnal atmospheric oxidation of NO₃ and N₂O₅ were conducted at a suburban site in Changzhou in the YRD using cavity ring-down spectroscopy (CRDS) from 27 May to 24 June, 2019. High concentrations of NO₃ precursors were observed, and the nocturnal production rate of NO₃ was determined to be 1.7 ± 1.2 ppbv/hr. However, the nighttime NO₃ and N₂O₅ concentrations were relatively low, with maximum values of 17.7 and 304.7 pptv, respectively, illustrating the rapid loss of NO₃ and N₂O₅. It was found that NO₃ dominated the nighttime atmospheric oxidation, accounting for 50.7%, while O₃ and OH only contributed 34.1% and 15.2%, respectively. For the reactions of NO₃ with volatile organic compounds (VOCs), styrene was found to account for 60.3%, highlighting its dominant role in the NO₃ reactivity. In general, the contributions of the reactions between NO₃ and VOCs and the N₂O₅ uptake to NO₃ loss were found to be about 39.5% and 60.5%, respectively, indicating that N₂O₅ uptake also played an important role in the loss of NO₃ and N₂O₅, especially under the high humidity conditions in China. The formation of nitrate at night mainly originated from N₂O₅ uptake, and the maximum production rate of NO₃⁻ reached 6.5 ppbv/hr. The average NO_x consumption rate via NO₃ and N₂O₅ chemistry was found to be 0.4 ppbv/h, accounting for 47.9% of the total NO_x removal. The predominant roles of NO₃ and N₂O₅ in nitrate formation and NOx removal in the YRD region was highlighted in this study.     

Enhanced debromination of 4-bromophenol by the UV/sulfite process: Efficiency and mechanism

Halogenated aromatic compounds have attracted increasing concerns due to their toxicity and persistency in the environment, and dehalogenation is one of the promising treatment and detoxification methods. Herein, we systematically studied the debromination efficiency and mechanism of para-bromophenol(4-BP) by a recently developed UV/sulfite process. 4-BP underwent rapid degradation with the kinetics accelerated with the increasing sulfite concentration, pH(6.1–10) and temperature, whereas inhibited by dissolved oxygen and organic solvents. The apparent activation energy was estimated to be 27.8 kJ/mol. The degradation mechanism and pathways of 4-BP were explored by employing N_2O and nitrate as the electron scavengers and liquid chromatography/mass spectrometry to identify the intermediates. 4-BP degradation proceeded via at least two pathways including direct photolysis and hydrated electron-induced debromination. The contributions of both pathways were distinguished by quantifying the quantum yields of 4-BP via direct photolysis and hydrated electron production in the system. 4-BP could be readily completely debrominated with all the substituted Br released as Br-, and the degradation pathways were also proposed. This study would shed new light on the efficient dehalogenation of brominated aromatics by using the UV/sulfite process.     

改性凹凸棒石处理痕量硝基苯废水

研究了用聚二甲基二烯丙基氯化铵（PDMDAAC）改性凹凸棒石对微污染水中痕量硝基苯的吸附性能、影响因素及其再生后吸附效果。结果表明：PDMDAAC改性凹凸棒石对微污染水中痕量苯酚具有较强的吸附能力,在pH＝8、硝基苯浓度为50μg／L、投加量为5g／L、吸附时间30min的条件下,吸附去除率达73％;改性后的凹凸棒石可用碱进行再生,再生后对硝基苯的吸附能力没有明显下降;改性凹凸棒石的等温静态吸附曲线呈线性关系。     

工业废水综合回用的实验研究

以保定市某渠工业废水为研究对象,调查了污水的主要来源和主要污染物,提出了处理方案:首先采用酸改性粉煤灰进行混凝,活性炭吸附,最后用臭氧进行氧化。同时探讨了酸改性粉煤灰的制备和最佳运行条件,活性炭的最佳运行条件和臭氧的最佳氧化时间,从而探索出一条适合于该渠工业废水的综合回用方法。     

中国地表水重金属污染的进展研究

为了解中国地表水重金属污染现状,并为水体重金属的治理提供一定依据,通过对地表水体重金属来源、中国各地区地表水重金属污染状况、水体重金属污染防治现状、风险及趋势分析和防治对策这五个方面进行综述.道路雨水径流的无处理排放易造成地表水体重金属的污染;中国许多地区的河流、湖泊等水体都存在重金属污染现象,不同地区污染来源不同,外源污染物输入是重要因素;致癌物镉、铬和砷对人体的健康风险要远远大于非致癌物.     

矩形空心钢筋混凝土桥墩抗震性能试验研究综述

桥墩的抗震性能试验是桥梁抗震分析的基础性研究工作。考虑到空心截面的优越性和地震时地面运动的多维性,通过拟静力试验研究双向水平地震作用下矩形空心钢筋混凝土桥墩的抗震性能具有十分重要的意义。文章从单向水平地震作用下桥墩的抗震性能、双向水平地震作用下桥墩的抗震性能、单双向水平地震作用下桥墩抗震性能的比较这三个方面进行了综述。     

Exploring the impact of new particle formation events on PM2.5 pollution during winter in the Yangtze River Delta, China

New particle formation（NPF） events are an increasingly interesting topic in air quality and climate science. In this study, the particle number size distributions, and the frequency of NPF events over Hefei were investigated from November 2018 to February 2019. The proportions of the nucleation mode, Aitken mode, and accumulation mode were 24.59%,53.10%, and 22.30%, respectively, which indicates the presence of abundant ultrafine particles in Hefei. Forty-six NPF events occurred during the obser...     

新疆生产建设兵团土壤环境质量状况研究

通过测定新疆生产建设兵团土壤中13种重金属元素以及3种有机物含量,计算单项污染指数并对各采样点土壤污染程度进行分级。结果表明,新疆生产建设兵团土壤总体上末受明显污染。