Ultrasonic adsorption

In oil-rich systems, the interpenetration of the interfacial layers allows to explain the origin of the attractive Van der Waals interactions and to describe the behavior of the conductivity (opening of pores). This picture is corroborated by ultrasonic adsorption experiments which show a strong adsorption near S2. This maximum of the ultrasonic adsorption is well accounted for by the exchanges of surfactants in the microemulsion phase, these exchange becoming more and more important as the interactions increase leading to a critical point. 

In the case of the water-rich systems, the approach to the critical point seems to be quite different. Ultrasonic adsorption experiments show no evidence of surfactant exchange even close to the boundary Sj(18). We rather observe an elongation of the droplets. In those systems, entropic forces must be dominant as evidenced by the study of a simpler system. 

The use of the surface ultrasonic waves seems to be convenient for these purposes. However, this method has not found wide practical application. Peculiarities of excitation, propagation and registration of surface waves created before these time great difficulties for their application in automatic systems of duality testing. It is connected with the fact that the surface waves are weakened by soil on the surface itself In addition, the methods of testing by the surface waves do not yield to automation due to the difficulties of creation of the acoustic contact. In particular, a flow of contact liquid out of the zone of an acoustic line, presence of immersion liquid, availability of chink interval leads to the adsorption and reflection of waves on tlie front meniscus of a contact layer. The liquid for the acoustic contact must be located only in the places of contact, otherwise the influence on the amplitude will be uncontrolled. This phenomenon distorts the results of testing procedure. 

It is also observed in Fig. 5.3 that Pd(II) ions are partly adsorbed on AI2O3 before ultrasonic irradiation the concentration of Pd(II) just before irradiation becomes ca. 0.8 mM, although 1 mM Pd(II) was added in the sample solution. From a preliminary adsorption experiment, the rate of Pd(II) adsorption on A1203 was found to be slow compared with those of Pd(II) reduction in the presence of alcohols. Therefore, it is suggested that the sonochemical reduction of Pd(II) in the presence of alcohols mainly proceeds in the bulk solution. The mechanism of the Pd/Al203 formation is also described in the section of sonochemical synthesis of supported metal nanoparticles. 

Breitbach M, Bathen D (2001) Influence of ultrasound on adsorption processes. Ultrason Sonochem 8(3) 277-283... 

Sonawane S, Chaudhari P, Ghodke S, Ambade S, Gulig S, Mirikar A, Bane A (2008) Combined effect of ultrasound and nanoclay on adsorption of phenol. Ultrason Sonochem 15 1033-1037... 

Gao, X. D. Li, X. M. Yu, W. D. 2004. Morphology and optical properties of amorphous ZnS films deposited by ultrasonic-assisted successive ionic layer adsorption and reaction method. Thin Solid Films 468 43 17. 

Electrokinetic Measurements. Electrophoretic mobilities were measured with a flat-cell apparatus manufactured by Rank Brothers, Cambridge, England. In addition, several mobility values were checked for accuracy with a Zeta Meter, New York. Mobilities were determined with a small volume of the suspension (approximately 25 cc) that had been prepared for the adsorption experiments. The pH of the solution was measured prior to determining the electrophoretic mobilities, which involved measuring the velocities of five to ten particles in each direction. An average value of the mobilities was recorded. Samples containing the flocculated particles were dipped into an ultrasonic bath for approximately one second prior to making the pH and mobility measurements. 

The adsorption and ultrasonic desorption of heavy metals on bentonites was studied by factorial designs... 

O. Lacin, B. Bayrak, O. Korkut and E. Sayan, Modeling of adsorption and ultrasonic desorption of cadmium(n) and zincflI) on local bentonite, J. Colloid Interface Sci., 292(2), 2005, 330-335. 

Figure 1. Adsorption of SDS on Graphon at 25° from aqueous solution after end-over-end action O and after ultrasonic irradiation X, and from solutions in 0.1M sodium chloride % (end-over-end)...

Selective adsorption on cellulose phosphate CM-cellulose chromatography Centrifugation on sucrose gradient Electrophoresis on sucrose gradient Ultrasonic disintegration DEAE-cellulose chromatography Gel filtration... 

Strano MS, Moore VC, Miller MK, Allen MJ, Haroz EH, Kittrell C, Hauge RH, Smalley RE. The role of surfactant adsorption during ultrasonication in the dispersion of single-walled carhon nanotubes. Journal of Nanoscience and Nanotechnology 2003, 3, 81-86. 

There are many other indirect techniques for determining colloidal species size or size distribution. These include sedimentation/centrifugation, conductivity, x-ray diffraction, gas and solute adsorption, ultrafiltration, viscometric, diffusiometric, and ultrasonic methods [12,13,26,69,82], Two reasons for the large number of techniques are the range of properties that can be influenced by the size of dispersed species, and the wide range of sizes that may be encountered. The grains in soils and sediments can range from colloidal size up to the size of boulders. 

Reversible attachment of nanostructures at molecular printboards was exemplified by the adsorption and desorption of CD-functionalized nanoparticles onto and from stimuli-responsive pre-adsorbed ferrocenyl-dendrimers at a CD SAM (Fig. 13.7).65 Electrochemical oxidation of the ferrocenyl endgroups was employed to induce desorption of the nanostructure from the CD SAM. An in situ adsorption and desorption of ferrocenyl dendrimers and CD-functionalized Au nanoparticles (d 3 nm) onto and from the molecular printboard was observed by a combination of surface plasmon resonance spectroscopy (SPR) and electrochemistry. Similar behavior was observed when larger CD-functionalized silica nanoparticles (d 60 nm) were desorbed from the surface with the aid of ultrasonication. 

Glass slides with the dimensions of 76 x 26 x 1 mm were used as supports for the multilayers. The slides were thoroughly cleaned by a mixture of sulfuric acid and potassium dichromate at 80 °C for about 2 hours in an ultrasonic bath prior to the films deposition. The initial concentration co of polyelectrolytes in the solution was 1 x 10 2 mole of the repeating units per liter. The pH value of the solution was about 6. Adsorption was carried out at room temperature in open glass beakers of 100 mL without stirring for 20 min. After every deposition step, the glass slides were rinsed three times for 1 min with Millipore Milli-Q water. The substrate was not dried between the adsorption steps. 

Metal sheets were degreased with ethanol in an ultrasonic bath, washed with distilled water, and dipped for 5 min in the 1 w/w % polymer solution. To remove the polymer excess the adsorbates were rinsed for 2 sec with distilled water. The adsorption procedure for sheets is summarized in Scheme 3. 

---