Aerosol silica

Reproduced from Transactions of Faraday Society, 62, Hambleton FH, Hockey JA, Infra-red spectroscopic investigation of the interaction of BCI3 with aerosol silicas, 1694-1701, 1966, with permission from the Royal Society of Chemistry. 

Figure 20. Fe3+ sorption on aerosol silica samples as function of surface sorption density. EXAFS Fourier transform functions. Indicated values are in pM/M2. 1 ML is approximately 3 pM/m2.

Silicone rnbbers have low strength and extensibility, which are increased by adding fillers (especially aerosol silicas) to about half that of hydrocarbon... 

Added filler will increase the viscosity and resistance to flow of a polymer. This is essential in adhesives, which would drain out of the joint by gravity or be sucked out of the glue line by capillary attraction. Viscosity increase becomes larger as the particle size is reduced. Fumed (aerosol) silica, a filler that introduces a structure to the liquid, can produce a thixotropic mixture (Anon, n.d. Byrne, 1984). Ease of handling of a liquid adhesive can be improved by additions to the polymer of 3-10% of its own weight in silica. The thickening effect is greatest in non-polar solvents when the powder is well dispersed. 

Another example is the use of Ti[0Si(0 Bu)3]4 that yielded Ti02-4 Si02, a good catalyst for cyclohexene epoxidation by cumylhydroperoxide (ROOH). Treatment of Ti[0Si(0 Bu)3]4 with aerosol silica, however, provided a material with 1.01 wt% Ti that, after calcination at 573 K, was more active (5.28 mmol g" min" ) and selective for this reaction (94.4% yield after 2 h at 338 K). This catalyst was twice as active as the Shell catalyst which consists of silica treated with [Ti(0 Pr)4]. ... 

Absher MP, Hemenway DR, Leslie KO et al (1992) Intrathoracic distribution and transport of aerosolized silica in the rat. Exp Lung Res 18 743-757... 

The inductively coupled plasma source (Fig. 20.11) comprises three concentric silica quartz tubes, each of which is open at the top. The argon stream that carries the sample, in the form of an aerosol, passes through the central tube. The excitation is provided by two or three turns of a metal induction tube through which flows a radio-frequency current (frequency 27 MHz). The second gas flow of argon of rate between 10 and 15 L min-1 maintains the plasma. It is this gas stream that is excited by the radio-frequency power. The plasma gas flows in a helical pattern which provides stability and helps to isolate thermally the outside quartz tube. 

First attempts to incorporate pre-formed magnetite colloids within alginate/silica nanocomposites via a spray-drying process have been described, but formation of lepidocrocite y-FeOOH and fayalite Fe2Si04 was observed, attributed to Fe2+ release during the aerosol thermal treatment [53],... 

Arriagada, F.J., and Osseo-Asare, K. (1995) Synthesis of nanosize silica in aerosol OT reverse microemulsions./. Colloid Interface Sci. 170, 8-17. 

I,, = 0.7 h on silica gel, tA = 2.2 h on alumina and tA = 44 h on fly ash for different atmospheric particulate substrates determined in the rotary photoreactor (appr. 25 pg/g on substrate) (Behymer Hites 1985) direct photolysis tA = 9.08 h (predicted-QSPR) in atmospheric aerosol (Chen et al. 2001). Photodegradation k = 3 x 10-5 s in surface water during the summertime at mid-latitude (Fasnacht Blough 2002)... 

Arriagada FJ, Osseoasare K (1994) Silica Nanoparticles Produced in Aerosol Ot Reverse Microemulsions - Effect of Benzyl Alcohol on Particle-Size and Polydispersity. J Dispers Sci Technol 15 59-71... 

Aerosol exposures were at 6, 20, and 60 mg/rn for 5 min on days 6-13 of pregnancy in rats and days 6-18 of pregnancy in rabbits. Control aerosols consisted of water or suspensions of Neosil (silica dust), and the experiments were conducted with 12-24 animals. The adults were killed a day before parturition rat fetuses were examined for 18 abnormalities and rabbit fetuses for eight abnormalities. In addition, rats were studied for teratogenic effects after exposure to CS by intraperitoneal injection at 20 mg/kg on day 6, 8, 10, 12, or 14 of pregnancy. 

Fig. 1.5.3 Aerosol generator assembly for the production of composite or coated particles (a) carrier gas (e.g., helium) tank, (b) drying column containing silica gel and molecular sieve, (c) Millipore membrane of 0.1 p.m pore size, (d) flow meters, (e) nuclei (e.g., NaCI, AgCI) generator, (f) and (m) boilers containing different reactant liquids, (g) and (n) condensation chambers, (h) heater, (i) chamber for recondensation of droplets, (q) and (e) coreactant containers, (k) and (p) vapor injection ports, (I) and (g) reaction chambers, (r) powder collector. (From Ref. 39.)...

Mesh Size. An interesting point noted by the data in Figure 5 is that the silica gel with the larger mesh size, 20-40, was a better collector of the acid mists than the smaller 35-60 mesh. This may be explained by a combination of the absorbing properties of the silica gel and the fact that the particles are liquid. It is speculated that the larger granules may better absorb and hold the liquid droplets of the aerosol once they are encountered. 

Breakthrough Study. The silica gel sampling tube has been optimized for the collection of aerosol-forming acid mists as well as vapor-forming acids. Now its capability for collecting at least a 4-hour air sample must be determined. 

Sampling and Analytical Precision and Accuracy. The accuracy of results obtained from a sampling and analytical method are determined by comparison with an independent method. The aerosols of phosphoric and sulfuric acids were collected on mixed cellulose ester filters (14 ) and analyzed by ion chromatography. Table V shows the collection efficiency of the 7-mm O.D./700-mg silica gel collection tubes with respect to the results obtained from filter samples, and the precision obtained from calculation of the pooled relative standard deviation. 

This work has demonstrated that sorbent tubes are viable samplers for inorganic acid mists existing as vapors and aerosols. A silica gel sampling tube was developed which will collect at least a 4-hour sample of inorganic acid at a nominal flow rate of 0.2 Lpm. The optimum sampler geometry was determined to be a 7-mm O.D./4.8-mm I.D. glass tube packed with 20-40 mesh washed silica gel, 700 mg in the primary section and 200 mg in the backup. 

The Lee and Gieseke model (8) for predicting aerosol collection on packed beds assumes that the volume fraction, or solidity, of the packed bed approaches 5/8, and applies to the collection by the packed bed only. Since the silica gel collection tube has a volume fraction of one-half or less, and since the greater percentage of the aerosol is collected on the initial glass wool plug, the model is not applicable to our sampler design. 

Dusts, Mists, Aerosols and Fumes. The P-5 Digital Dust Indicator is another sensor currently available for use as a component of the Chronotox System. Suitable for the measurement of silica, lead fumes, pharmaceutical powders as well as many other types of particulates found in manufacturing or laboratory situations, the battery-operated P-5 uses the light scattering technique to measure dusts over a range of either 0.01-100 mg/m or 0.001-10 mg/m (Figure 6). 

Figure 22-18 shows tin electrospray interface for capillary electrophoresis. The silica capillary is contained in a stainless steel capillary held at the required outlet potential for electrophoresis. The steel makes electrical contact with the liquid inside the silica by a liquid sheath flowing between the capillaries. The sheath liquid, which is typically a mixed organic/ aqueous solvent, constitutes —90% of the aerosol. 

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