Microwave-assisted continuous flow phytosynthesis of silver nanoparticle/reduced graphene oxide composites and related visible light catalytic performance

The creation of an environmentally friendly synthesis method for silver nanomaterials (AgNPs) is an urgent concern for sustainable nanotechnology development. In the present study, a novel straightforward and green method for the preparation of silver nanoparticle/reduced graphene oxide (AgNP/rGO) composites was successfully developed through the combination of phytosynthesis, continuous flow synthesis and microwave-assistance. Oriental persimmon (Diospyros kaki Thunb.) extracts were used as both plant reducing and capping agents for fast online synthesis of AgNP/rGO composites. The experimental parameters were optimized and the morphologies of the prepared materials were investigated. The characterization results reveal that spherical AgNPs were quickly synthesized and uniformly dispersed on rGO sheets using the proposed online system. Fourier transform infrared spectroscopy analysis confirmed that phenols, flavonoids, and other substances in the plant extracts played a decisive role in the synthesis of AgNP/rGO composites. Using sodium borohydride (NaBH₄) degradation of p-nitrophenol (4-NP) as a model, the catalytic activity of the prepared AgNP/rGO materials was evaluated. The complete degradation of 4-NP was achieved within 12 min through the use of AgNP/rGO materials, and the composite had a much better catalytic activity than the bare AgNPs and rGO had. Compared with the conventional chemical method, our online method is facile, fast, cost-efficient, and environmentally friendly.     

Diel Cycling of Zinc in a Stream Impacted by Acid Rock Drainage: Initial Results from a New in situ Zn Analyzer

Recent work has demonstrated that many trace metals undergo dramatic diel (24-h) cycles in near neutral pH streams with metal concentrations reproducibly changing up to 500% during the diel period (Nimick et al., 2003). To examine diel zinc cycles in streams affected by acid rock drainage, we have developed a novel instrument, the Zn-DigiScan, to continuously monitor in situ zinc concentrations in near real-time. Initial results from a 3-day deployment at Fisher Creek, Montana have demonstrated the ability of the Zn-DigiScan to record diel Zn cycling at levels below 100 μg/l. Longer deployments of this instrument could be used to examine the effects of episodic events such as rainstorms and snowmelt pulses on zinc loading in streams affected by acid rock drainage.     

连续流动-固相微萃取方法富集水中多环芳烃的探讨

建立了连续流动-固相微萃取富集、气相色谱测定水中多环芳烃的方法,探讨了流量和溶液体积对萃取效果的影响。方法在0μg／L-40μg／L范围内线性良好,8种多环芳烃的检出限为0．05μg／L-0．5μg／L,样品测定的相对标准偏差〈7％,加标回收率为87．0％～112％。     

小风和静风状态下连续体源大气扩散模式的理论推导

以小风和静风状态下连续点源的大气扩散模式为基础,采用与体源烟团的初始分布尺度相当的初始时间修正其扩散参数公式中的运行时间,从理论上导出了小风和静风状态下连续体源的大气扩散模式。该模式与现有的大气扩散模式体系完全相容,可以方便地应用于小风和静风状态下连续体源引起的地面浓度的预测计算。     

Continuous nitrifying granular sludge bioreactor: Influence of aeration and ammonium loading rate

Granulation of nitrifying bacteria was investigated in a continuous bubble column bioreactor. Then, the combined effect of aeration and ammonium loading rates on dissolved oxygen (DO) concentration as well as nitrification process was evaluated in the system using an experimental design technique. After 120 days, stable nitrifying granules with average diameter of 1.4 mm and settling velocities of 55 m/h were obtained. The influence of increasing ammonium loading rate (ALR) was found to be more significant than decreasing aeration rate on the reduction of DO concentration inside the nitrifying bioreactor. The system could handle the ALR values of 0.48–1.92 gNH₄⁺-N/L d with the ammonium removal efficiency from 65% to nearly 100% at the tested airflow rates of 2.5 and 4.5 L/min. At the low aeration, the complete ammonium conversion to nitrate was replaced with nitrite when the ALR increased to 1.44 gNH₄⁺-N/L d. At the high aeration, however, almost complete nitrification was achieved except the high ALR in which the nitrite accumulation was observed up to 38%. The study demonstrated that the continuous bioreactor had a considerable performance for obtaining stable nitrifying granules to have nitrite accumulation under control with changing the ratio of aeration rate and ALR.     

事故过程的确定性混沌分析方法

综述了对事故致因理论的研究现状 ;提出了系统事故过程的确定性混沌分析方法 ;介绍了混沌分析方法的计算步骤 ;并以矿井火灾过程进行了实例分析。结果表明 :这种方法可对事故过程的系统状态进行连续分析。     

An experimental and modeling study of continuous liquid fuel spill fires on water

The spread of burning fuel spilled from oil product containers during offshore storage and transportation may cause large damage and trigger further accidents. Some analytical models already exist to predict the spread and burning behavior of liquid fuel spill fires, however, few experimental studies have been conducted to verify the model results. In this paper, continuous n-heptane spill fire experiments were conducted in a rectangular trench covered with water. The burning area, fuel spread rate, and thermal flux with different discharge flow rates and ignition delay times were investigated by both experimental and modeling means. The spill fire burning area, with 5 typical phases during burning, has a quasi-steady value which is directly proportional to the discharge rate but irrelevant to the ignition delay times. The steady burning rate, as the ratio of discharge rate over burning area, was estimated. A spread model was modified to simulate the spread of continuous liquid fuel spill fires in a one-dimensional channel, based on the balance between gravity and viscous forces. A cuboid solid flame model was used to compute the thermal flux from spill fires. The burning fuel spread and the heat flux calculated by the models agree with the experimental results.     

呼和浩特市环境空气24小时连续监测(湿法)与自动监测(干法)的对比分析

武汉虹TH-3000微电脑大气污染日平均浓度采样器与美国Dasibi公司生产的Dasibi1000型大气自动监测系统，监测方法不同。本文对两系统监测SO2、NO2、结果进行对比分析，表明：①两种监测系统测定SO2和NO2都具有很好的线性关系；②测定结果之间存在着显著性差异；③两种监测系统间存在着系统误差；④SO2测定结果不具有相同的精密度，而NO2却具有很好的精密度；⑤两种监测系统监测SO2和NO2的平均偏差较大。     

Effects of dissolved inorganic carbon and nutrient levels on carbon fixation and properties of Thermosynechococcus sp. in a continuous system

The concept of CO₂ chemo-absorption by sodium hydroxide in a wet scrubber followed by microalgae cultivation was used as a means to reduce the major greenhouse gas. A thermophilic and alkaline tolerable cyanobacterium named Thermosynechococcus CL-1 (TCL-1) was cultivated in continuous system, with a carbonate-bicarbonate buffer as carbon source. The effects of dissolved inorganic carbon (DIC_in) and nutrient levels in influent on cell mass productivity, DIC removal efficiency, and alkaline solution regeneration by TCL-1 were investigated. The results show the highest cell mass productivity reaches 1.7 g L⁻¹ d⁻¹ under the highest DIC and nutrients level. Conversely, the best regeneration of alkaline solution proceeds from pH 9.5 to 11.3 under the lowest level. In addition, the highest ΔDIC (DIC consumption) and DIC removal efficiency are 42 mM and 43% at 113.2 and 57 mM DIC_in, respectively.     

基于升流式厌氧污泥床反应器的微生物燃料电池的研究

构建了一种基于升流式厌氧污泥床反应器（UASB）的微生物燃料电池（MFCs）,利用UASB高效去除COD能力及连续进样方式,获得稳定电能输出。考察了水力停留时间、进液方式、电极材料、离子交换膜种类、溶液离子强度等因素对于MFCs性能的影响。实验结果表明：在水力停留时间6h、连续进液、高纯石墨板电极以及均相阳离子交换膜条件下,连续运行3个月,放电功率稳定在145mW／m^2,开路电压0．78V,放电电流最高可达321mA／m^2。