Agitation ultrasonic

When ultrasound emitter and electrode are different elements in the system, electrode-apart-transducer configuration, Fig. 4.2a, ultrasound removes the nanoparticles from the cathode to form suspended seeds. The ultrasonic agitation maintains a suspension of these preformed nanoparticles, which move continuously around, hit the electrodes, and these charged particles attach to one another and grow in suspension [90]. In this case, ultrasound keeps the larger structures from agglomeration. 

Prasad PBSN, Vasudevan R, Seshadri SK (1994) Effect of ultrasonic agitation on surface finish of electrodeposits Indian. J Eng Mater Sci 1 178-180... 

For the analysis of organic additives in polymeric materials, in most cases, prior extraction will be necessary. Depending on the nature of the additive, many different approaches are employed. These include soxhlet extraction with organic solvent or aqueous media, total sample dissolution followed by selective precipitation of the polymer leaving the additive in solution, assisted extraction using pressurised systems, ultrasonic agitation and the use of supercritical fluids. In trace analysis, solid phase extraction (SPME) from solution or solvent partition may be required to increase the analyte concentration. 

In addition, there are a few examples of heterogeneous nonaqueous sonochemistry, in both liquid-liquid and liquid-solid systems. Two recent reports have utilized ultrasonic agitation in place of or along with phase transfer catalysis for the preparation of dichlorocarbene from aqueous NaOH/CHCl3 (166), and for N-alkylation of amines with alkyl halides (167). Along the same lines, several papers have appeared in which... 

Besides the advantage of recyclability, reactions in ionic liquids are generally faster and are run under milder conditions than reactions with conventional solvents. Further activation may come from ultrasonic agitation.520 Since the majority of ionic liquids used are imidazolium salts, the effect of these solvents can be at least partly attributed to the in situ formation of carbene complexes (Section 9.6.3.4.10).521 Cross-coupling of ArB(OH)2 can also be efficiently performed in ionic liquids based on long-chain tetraalkylphosphonium salts, in which case aryl bromides and some aryl chlorides can be processed in the presence of the trivial ligand PPh3.522... 

Matthews and Riley [99] preconcentrated iodide by co-precipitation with chloride ions. This is achieved by adding 0.23 g silver nitrate per 500 ml of seawater sample. Treatment of the precipitate with aqueous bromine and ultrasonic agitation promote recovery of iodide as iodate which is caused to react with excess iodide under acid conditions, yielding I3. This is determined either spectrophotometrically or by photometric titration with sodium thiosulfate. Photometric titration gave a recovery of 99.0 0.4% and a coefficient of variation of 0.4% compared with 98.5 0.6% and 0.8%, respectively, for the spectrophotometric procedure. 

The best results were obtained using collector DAS-2, consisting of xanthated fatty acid + amine. The reagent was prepared by ultrasonic agitation of xanthate (50%), fatty acid (25%) and amine (25%). The mixture is a yellow-coloured solution. 

Soil extraction using all types of aqueous solutions and ultrasonic agitation has been carried out. Simple apparatus such as extractant and aqueous solvent in an Erlenmeyer flask or test tube are used. An ultrasonic bath with Erlen-meyer flask is shown in Figure 11.7 (the use of an ultrasonic horn is shown in Figure 12.9). Ultrasonic extraction is typically carried out when the soil particles are not well separated, such as high clay soils, and thus the surfaces are not exposed to the extracting solutions. 

Ultrasonic agitation during leaching has recently been reported to increase the catalytic activity of skeletal nickel for the hydrogenation of benzene to cyclohexane, with the enhanced activity related to changes in the catalyst structure and surface species [47],... 

Recently, it has been shown that ultrasonic agitation during hydrogenation reactions over skeletal nickel can slow catalyst deactivation [122-124], Furthermore, ultrasonic waves can also significantly increase the reaction rate and selectivity of these reactions [123,124], Cavitations form in the liquid reaction medium because of the ultrasonic agitation, and subsequently collapse with intense localized temperature and pressure. It is these extreme conditions that affect the chemical reactions. Various reactions have been tested over skeletal catalysts, including xylose to xylitol, citral to citronellal and citronellol, cinnamaldehyde to benzenepropanol, and the enantioselective hydrogenation of 1-phenyl-1,2-propanedione. Ultrasound supported catalysis has been known for some time and is not peculiar to skeletal catalysts [125] however, research with skeletal catalysts is relatively recent and an active area. 

The HPLC pump draws the mobile phase from the reservoir via vacuum action. In the process, air dissolved in the mobile phase may withdraw from the liquid and form bubbles in the flow stream unless such air is removed from the liquid in advance. Air in the flow stream is undesirable because it can cause a wide variety of problems, such as poor pump performance or poor detector response. Removing air from the mobile phase, called degassing, in advance of the chromatography is a routine matter, however, and can be done in one of several ways 1) helium sparging, 2) ultrasonic agitation, 3) drawing a vacuum over the surface of the liquid, or 4) a combination of numbers 2 and 3. 

Stirring is one obvious solution and this method is adopted commercially [5]. However the fastest form of stirring is ultrasonic agitation. Applying ultrasound has been found to decrease the thickness of this diffusion layer, and so assist the electrode reaction (Fig. 6.8). 

Uneven reduction of it ULTRASONIC AGITATION Fig. 6.8. Disturbance of diffusion layer. 

Walker [9] has studied the effect of ultrasonic agitation in terms of hardness, quality of deposit and efficiency. Using spent zincate plating baths, he observed that both the efficiency of the zinc recovery process and the maximum current density which could provide for good quality deposits was significantly increased in the presence of ultrasound (Tab. 6.7). He also observed that the improvement was inversely dependent on the bath concentration the more dilute was the bath (0.5 g dm zinc) then the greater the improvement. 

An example of a schematic for sample treatment, extraction, and separation procedures is given in Simoneit, and it follows the method first used by Simoneit and Mazurek with minor modifications for data comparison purposes. The samples are powdered and dried, then typically extracted using ultrasonic agitation multiple times with a mixture of dichloromethane (CH2CI2) and methanol (3 1 v/v). The solvent extracts are filtered through an annealed glass fiber filter for the removal of insoluble particles, concentrated by rotary evaporation and then by a stream of filtered nitrogen gas. 

Phospholipid vesicles form spontaneously when distilled water is swirled with dried phospholipids. This method of preparation results in a highly polydisperse array of multicompartment vesicles of various shapes. Extrusion through polymeric membranes decreases both the size and polydispersity of the vesicles. Ultrasonic agitation is the most widely used method for converting the lipid dispersion into single-compartment vesicles of small size. 

Sonication in the presence of solvent is also an alternative, very effective procedure to maximize extraction yield. Ultrasonic agitation allows more intimate... 

Figure 26-40 Integrated biochip for DNA analysis of biological samples. Dimensions are 100 x 60 x 2 mm. Two bright circles are piezoelectric vibrators for ultrasonic agitation. 

Sample and immunomagnetic capture beads are mixed by ultrasonic agitation... 

Degas the mobile phase via vacuum filtration, ultrasonic agitation, or inline vacuum degasser. 

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