Toward efficient interactions of bubbles and coal particles induced by stable cavitation bubbles under 600 kHz ultrasonic standing waves

The interactions of bubbles and coal particles in 600 kHz ultrasonic standing waves (USW) field has been investigated. A high-speed camera was employed to record the phenomena occurred under the USW treatment. The formation and behaviors of cavitation bubbles were analyzed. Under the driving of these cavitation bubbles, whose size is from several microns to dozens of microns, coal particles were aggregated and then attracted by large bubbles due to the acoustic radiation forces. The results of USW-assisted flotation show a significant improvement in recoveries at 600 kHz, which indicates that the interactions of bubbles and particles in the USW field are more efficient than that in the conventional gravitational field. Furthermore, the sound pressure distribution of the USW was measured and predicted by a hydrophone. The analysis of gravity and buoyancy, primary and secondary Bjerknes forces shows that bubble-laden particles can be attracted by the rising bubbles under large acoustic forces. This study highlights the potential for USW technology to achieve efficient bubble-particle interactions in flotation.     

Ultrasonic assisted functionalization of MWCNT and synergistic electrocatalytic effect of nano-hydroxyapatite incorporated MWCNT-chitosan scaffolds for sensing of nitrofurantoin

In the present work, we report the fabrication of stable composite of chitosan hydrogels (CHI) on multiwalled carbon nanotubes (MWCNT) using a simple ultrasonic-assisted method. Also, rod-like hydroxyapatite nanoparticles (HA NPs) were synthesised using a hydrothermal route and were incorporated into the highly conductive MWCNT-CHI scaffolds using an ultrasonication method. The functionalization of MWCNT and preparation of HA NPs on MWCNT-CHI nanocomposite were done using the sonication over the frequency of 37 kHz with the ultrasonic power capable of 150 W (Elmasonic Easy 60H bath sonicator). The resulting hybrid HA NPs/MWCNT-CHI nanocomposites have an excellent surface area and high surface to volume ratio, which leads to the sensitive detection of nitrofurantoin than pristine MWCNT and HA NPs. The complete elemental and morphological analyses of the HA NPs/MWCNT-CHI nanocomposites were characterised by XRD, FTIR, RAMAN, FESEM, TEM, EDX, and elemental mapping techniques. Electrochemical analysis of the HA NPs/MWCNT-CHI nanocomposites was carried out by cyclic voltammetry, electrochemical impedance spectroscopy and amperometry methods. The modified glassy carbon electrode (GCE) of HA NPs/MWCNT-CHI nanocomposites exhibit the nitrofurantoin detection activity at the linear range of 0.005–982.1 µM with the detection limit of 1.3 nM. The synergistic electrocatalytic activity of HA NPs/MWCNT-CHI nanocomposites modified GCE is correlated to the sensitivity of 0.16 µAµM⁻¹ cm⁻² with excellent precision and accuracy towards the sensing of nitrofurantoin.     

Ultrasound pre-fractured casein and in-situ formation of high internal phase emulsions

Traditional preparation of protein particles is usually complex and tedious, which is a major issue in the development of Pickering high internal phase emulsions (HIPEs). In this study, a facile and in-situ method for the preparation of food-grade Pickering HIPEs was developed using ultrasound pre-fractured casein flocs. The ultrasonic-treated casein protein and resulting Pickering HIPEs were characterised using particle size distribution, confocal laser scanning microscopy (CLSM), cryo-SEM, and rheological measurement. The results indicated that pH values of casein and ultrasonic power level were key parameters for casein protein dispersion into nanoparticles to form o/w Pickering HIPEs. In optimal conditions, the hexagons of emulsion droplets were close together, and the emulsions formed with ultrasonic caseins exhibited gel-like behaviour. Additionally, ultrasonic microscale-sized caseins (about 25 μm) disappeared upon the use of high speed homogenisation during the formation of HIPEs, while the chemical distribution revealed by confocal laser scanning microscopy indicated that the dispersive nanoparticles from casein proteins were evidently absorbed on the interface of HIPEs (cryo-SEM). These findings prove that ultrasound is an effective tool to loosen casein flocs to induce the in-situ formation of stabilised Pickering HIPEs. Overall, this work provides a green and facile route to convert edible oil into a soft solid, which has great potential for applications in biomedical materials, 3D printing technology, and various cosmetics.     

Intensification of delignification of Tectona grandis saw dust as sustainable biomass using acoustic cavitational devices

Delignification of sawdust was studied using ultrasound assisted alkali peroxide approach using longitudinal horn for the first time and the efficacy compared with more commonly used configurations of ultrasonic reactors. Comparison with the conventional approach based on stirring has also been presented to establish the process intensification benefits. Effect of different operating parameters such as sodium carbonate concentration (0.1, 0.15, 0.2, 0.25 M), hydrogen peroxide concentration (0.2, 0.4, 0.6, 0.8, 1 M) and biomass loading (2, 4, 6, 8, 10 wt%), on the efficacy of lignin extraction has been investigated for different ultrasonic reactors. The optimum conditions for probe type ultrasonic horn were established as 150 W, 50% duty cycle and 80% amplitude with optimum process conditions as Na₂CO₃ concentration as 0.2 M, H₂O₂ concentration as 1 M, biomass loading of 10 wt% and operating time of 70 min. Longitudinal horn resulted in best efficacy (both in terms of yield and energy requirements) followed by ultrasonic horn and ultrasonic bath whereas the conventional approach was least effective. The obtained lignin was also analyzed using different characterization techniques. The presence of peaks at wavelength range of 875–817, 1123–1110, and at 1599 cm⁻¹ for the extracted sample confirmed the presence of lignin. Increase in the crystallinity index of the processed sample (maximum for longitudinal horn) also confirmed the lignin removal as lignin is amorphous in nature. Overall it has been concluded that ultrasound can be effectively used for delignification with longitudinal horn as best configuration.     

Ultrasonic and Raman Scattering Spectroscopy of Zinc Thiocyanate Complexes in Water at 25<Superscript>∘</Superscript>C: Kinetics of Complex Formation Determined by Multivariate Analysis

Advances have been made recently in broadening the accessible ultrasonic absorption frequency range and improving the detectability of minor species present in solution using Raman spectroscopy. Development of chemometric techniques in these areas needs to keep pace with the improvement of these experimental methods. Refinements in the analysis of ultrasonic and Raman data based on multivariable least squares and factor analysis, respectively, are examined to investigate the kinetics of zinc thiocyanate complex formation in water. Analysis of ultrasonic absorption relaxation spectra verified that the observed process in aqueous Zn(SCN)₂ involves substitution of water from the first coordination shell of Zn²⁺. Use of a multivariable least-squares error surface is described that enhances the reliability of assigned frequencies of ultrasonic absorption maxima. Factor analysis of Raman scattering data provided direct evidence that at least four complex species, such as Zn(SCN)⁺ and Zn(SCN)₂, are simultaneously present in the aqueous zinc thiocyanate solutions.     

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.     

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.     

超细纳米Pd粒子与聚乙烯吡咯烷酮的相互作用

在微量聚乙烯吡咯烷酮(PVP)存在下, 利用超声还原氯化钯水溶液, 制备出超细纳米Pd颗粒, 用高分辨透射电镜、红外光谱、紫外-可见光谱和X射线光电子能谱等技术对其表面形貌及结构进行了表征. 结果表明, 纳米Pd粒子的粒径均一, 大约为3 nm. 纳米Pd/PVP复合粉末的羰基红外吸收峰比PVP的羰基吸收峰红移9 cm^-1; 且当超声反应50 min时, PVP紫外吸收波峰蓝移16 nm, 表明了纳米Pd与PVP之间存在一定的相互作用力. XPS结果证明, 纳米Pd与PVP的羰基基团通过配位作用使超细纳米Pd粒子得以稳定分散存在.     

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.     

超声萃取-高效液相色谱法同时测定人造革中7种苯并三唑类紫外线吸收剂含量

建立了超声萃取-高效液相色谱法(HPLC)同时测定人造革中7种苯并三唑类紫外线吸收剂UV-P、UV-326、UV-327、UV-329、UV-350、UV-320和UV-328含量的方法。该方法以甲醇为萃取溶剂,超声萃取人造革中的苯并三唑类紫外线吸收剂,萃取液经处理后直接进行HPLC分析,外标法定量。在信噪比(S/N)=3的条件下,UV-P、UV-326、UV-327、UV-329、UV-350的检出限均为0.05mg/kg,UV-320、UV-328的检出限均为0.10 mg/kg。在3个不同加标浓度水平下,各组分的平均加标回收率为88.19%~98.32%,相对标准偏差(RSD)为0.61%~3.74%。该方法简便快捷、灵敏度高,可用于人造革中苯并三唑类紫外线吸收剂的测定。采用该方法对市售人造革样品进行测定,结果在6个样品中检出了不同浓度水平的UV-P和UV-329。