Quantitative determination of 16 polycyclic aromatic hydrocarbons in soil samples using solid‐phase microextraction

A method for the determination of polycyclic aromatic hydrocarbons (PAHs) in soil samples using ultrasonic‐assisted extraction with internal surrogates combined with solid‐phase microextraction and GC‐MS has been developed. Five kinds of commercial solid‐phase microextraction fibers, 100 μm PDMS, 30 μm PDMS, 65 μm PDMS/DVB, 50 μm DVB/CAR/PDMS and 85 μm PA, were compared to choose the optimal SPME fiber for extraction of PAHs. One hundred micrometers of PDMS fiber was found to be more suitable for the determination of PAHs due to its wider linear range, better repeatability, lower detection and more satisfactory efficacy than the other fibers. Under the recommended conditions, 100 μm PDMS fiber could provide low nanogram level detection limits with correlation coefficient greater than 0.98. The method was also applied to determine PAHs in a spiked soil sample, obtaining recoveries higher than 79.3%. A field study with naturally contaminated samples from local contaminated sites was carried out. The proposed method was found to be a reliable, inexpensive and simple preparation method for quantitative determination of 16 PAHs in soil samples.     

污泥和沉积物中微量大环内酯类、磺胺类抗生素、甲氧苄胺嘧啶和氯霉素的测定

利用超声波辅助萃取(USE)技术,联合固相萃取(SPE)净化浓缩以及液相色谱-电喷雾串联质谱(LC-ESI-MS/MS)技术,建立了城市污泥和河流底泥中微量-痕量大环内酯类、磺胺类抗生素、甲氧苄胺嘧啶和氯霉素的多目标定量分析方法.样品经USE提取,SPE净化后,用LC-ESI-MS/MS检测.选择C18为分析柱,甲醇、5 mmol/L醋酸铵和0.1%甲酸混合溶液为流动相,选择在ESI正电离源下多反应监测(MRM)模式检测.对比了USE和加速溶剂萃取(ASE)对抗生素的萃取效率,优化了萃取条件.结果表明: USE和ASE对所选抗生素的萃取效率相当; 而50%甲醇溶液在酸性条件下(pH 2)萃取效率最好.抗生素的方法检出限为2.2～66.9 ng/g(干重,下同); 回收率介于74.7%～111.8%之间; 相对标准偏差小于10.6%.应用此方法在广州某污水处理厂脱水污泥及某河涌底泥中检测到磺胺二甲基嘧啶、克拉霉素、脱水红霉素及罗红霉素等多种抗生素,含量为6.8～125.6 ng/g.     

Non-invasive monitoring of fouling in hollow fiber membrane via UTDR

Fouling is the most critical problem associated with membrane separations in liquid media. But it is difficult to control the inevitable membrane fouling because of its invisibility, especially on the inside surface of hollow fiber membranes. This study describes the extension of ultrasonic time-domain reflectometry (UTDR) for the real-time measurement of particle deposition in a single hollow fiber membrane. A transducer with a frequency of 10 MHz and polyethersulfone hollow fiber membranes with 0.8 mm inside diameter (ID) and 1.2 mm outside diameter (OD) were used in this study. The fouling experiments were carried out with 1.8 g/L kaolin suspension at flow rates 16.7 and 10.0 cm/s. The results show that UTDR technique is able to distinguish and recognize the acoustic response signals generated from the interfaces water/upper outside surface of the hollow fiber, lumen upside surface/water, water/lumen underside surface and lower outside surface/water in the single hollow fiber membrane module in pure water phase. The systemic changes of acoustic responses from the inside surfaces of the hollow fiber in the time- and amplitude-domain with operation time during the fouling experiments were detected by UTDR. It is associated with the deposition and formation of the kaolin layer on the inside surfaces. Further, the acoustic measurement indicates that the deposited fouling layer is denser on the lumen underside surface of the hollow fiber than that on the lumen upside surface as a result of weight. Moreover, it is found that the fouling layer grows faster on the inside surface of the hollow fiber at a flow rate of 10.0 cm/s than that at 16.7 cm/s due to the lower shear stress. The fouling layer formed is thicker at a flow rate of 10.0 cm/s than that at 16.7 cm/s. The flux decline data and SEM analysis corroborate the ultrasonic measurement. Overall, this study confirms that UTDR measurement will provide not only a new protocol for the observation of hollow fiber membrane fouling and cleaning, but also a quantitative approach to the optimization of the membrane bioreactor system.     

超声波对制备Co-Fe/硅藻土选择加氢催化剂的影响

分别在有无超声条件下,采用分步浸渍法制备了负载型Co-Fe/硅藻土催化剂,以肉桂醛选择加氢为肉桂醇为探针反应,在固定床微分反应器上考察了催化剂的活性.采用热分析、红外、XRD及正电子寿命谱等技术分析了催化剂的催化性能及超声波对活性的影响.结果表明,经超声处理的催化剂对肉桂醛加氧为肉桂醇转化率、选择性和收率明显提高.超声处理没有改变催化剂载体的结构,但使主、助催化剂更好地分散在载体上,使催化剂表面的两类缺陷尺寸变小,同时增加第二类缺陷数量,有更好的催化活性.     

微波辅助萃取与超声波萃取丹参中丹酚酸B的比较研究

本文对微波辅助萃取和超声波萃取丹参中丹酚酸B进行了比较研究,并用高效液相色谱法(HPLC)测定了丹参中丹酚酸B.考察了微波辅助萃取和超声波萃取参数的影响,在各自最佳萃取条件下进行了丹参中的丹酚酸B提取率的比对,结果表明:微波辅助萃取6 min的提取率高于超声波萃取30 min的提取率.微波辅助萃取法与超声波萃取法相比具有省时、高效和溶剂用量少的特点.利用指纹图谱比较了两种萃取方式提取的化学成分的差异,结果显示两种萃取方法提取的主要成分组成基本相同,其共有成分比例相近.     

Ultrasonic assisted polyol synthesis of highly dispersed Pt/MWCNT electrocatalyst for methanol oxidation

A novel chemical method based on ultrasonic assisted polyol synthesis for the fabrication of highly dispersed Pt nanoparticles on multi-walled carbon nanotubes (MWCNTs) was developed. The simple and green method took only about 10 min at ambient temperature. The structure and chemical nature of the resulting Pt/MWCNT composites were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and energy dispersive X-ray spectrometry (EDS). The results showed that the prepared Pt nanoparticles were uniformly dispersed on the MWCNT surface. The mean size of Pt nanoparticles was about 2.8 nm. Electrochemical properties of Pt/MWCNT electrode for methanol oxidation were examined by cyclic voltammetry (CV) and excellent electrocatalytic activities could be observed. The possible formation mechanism of Pt/MWCNTs was also discussed.     

Opportunities and Challenges in the Use of TiO2 Nanoparticles Modified with Citric Acid to Synthesize Advanced Nanocomposites Based on Poly(amide-imide) Containing N,N′-(Pyromellitoyl)-bis-L-leucine Segments

In this study, the goal was the preparation, characterization, and surface morphology of poly(amide-imide)/TiO₂-citric acid nanocomposites (PAI/TiO₂-CA NCs). Owing to the high surface energy and tendency for agglomeration, the surface of TiO₂ nanoparticles was modified with citric acid. Then poly(amide-imide) was synthesized by direct polycondensation reaction of N,N′-(pyromellitoyl)-bis-L-leucine diacid with 4,4′-diaminodiphenylmethane by triphenyl phosphite and tetra-n-butylammonium bromide as a green medium. The attained polymer and modified TiO₂ nanoparticles were used to prepare PAI/TiO₂-CA NCs through ultrasonic irradiation. The resulting PAI/TiO₂-CA NC was characterized with FT-IR spectroscopy, X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, and thermogravimetric analysis.     

基于感知的右视点质量可分级编码算法

为了减少立体视频传输如此庞大的数据量，根据人眼的立体掩蔽效应，提出了基于感知的右视点质量可分级编码算法．该算法将宏块分为3类：平坦块、纹理块和边缘块，通过不同的量化步长使得右视点图像块的质量可分级．实验证明根据左视点的图像质量，右视点在人眼感知范围内码率减少25％～37％．该算法能在人眼主观察觉范围内很好地提高码率，进一步消除人眼立体视觉冗余．     

Non-contact evaluation of the resonant frequency of a microstructure using ultrasonic wave

This paper presents a novel non-contact method for evaluating the resonant frequency of a microstructure, Firstly, the microstructure under test is excited by ultrasonic waves. This excitation method does not impose any undefined load on the specimen like the electrostatic excitation and also this is the first actual use of ultrasonic wave for exciting a microstructure in the literature. Secondly, the amplitudes of the microstructure are determined by image edge detection using a Mexican hat wavelet transform on the vibrating images of the microstructure. The vibrating images are captured by a CCD camera when the microstructure is vibrated by ultrasonic waves at a series of discrete high frequencies （〉30 kHz）. Upon processing the vibrating images, the amplitudes at various excitation frequencies are obtained and an amplitude-frequency spectrum is obtained from which the resonant frequency is subsequently evaluated. A micro silicon structure consisting of a perforated plate （192 × 192 μm） and two cantilever beams （76 × 43 μm） which is about 4 μm thickness is tested. Since laser interferometry is not required, thermal effects on a test object can be avoided. Hence, the setup is relatively simple. Results show that the proposed method is a simple and effective approach for evaluating the dynamic characteristics of microstructures.     

Ultrasonic‐Assistance and Aging Time Effects on the Zeolitation Process of BZSM‐5 Zeolite

The isomorphic substitution of boron into ZSM‐5 zeolite under static hydrothermal condition was investigated. Evaluation of hydrothermal synthesis of BZSM‐5 was performed by treating the synthesis mixture by different aging processes, namely, ultrasonic, static, stirring, and microwave‐assisted aging prior to the conventional hydrothermal treatment. The synthetic processes with different techniques of aging prior to the onset of conventional hydrothermal crystallization were compared with a process without any prior aging. The obtained results showed that the ultrasonic and microwave assisted aging shortened the crystallization time and altered the crystal size and the morphology of the obtained products. The characteristics of the synthesized products were obtained by FT‐IR spectroscopic, XRD and SEM techniques.