Submicron particles

In addition, the PMio NAAQS will continue to place emphasis on quantifying and reducing particulate emissions in the less than 10- Im particle-size range. Particle size-specific emission factors have been developed for many sources, and size-specific emission standards have been developed in a number of states. These standards are addressing concerns related to HAP emissions of hea y metals, which are generaUy associated with the submicron particles. 

Sun, 1994. Jinjun Sun, Benjamin Liu, Peter McMurry, and Stephen Greenwood, A Method to Increase Control Efficiencies for Wet Scrubbers for Submicron Particles and Particulate Metals, J. Air Waste Management Association, 44 2, February 1994. 

Venturi. Submicron particles can Gases enter at cop. High or low gas and... 

Today microemulsions are used in catalysis, preparation of submicron particles, solar energy conversion, extraction of minerals and protein, detergency and lubrication [58]. Most studies in the field of basic research have dealt with the physical chemistry of the systems themselves and only recently have microemulsions been used as a reaction medium in organic synthesis. The reactions investigated to date include nucleophilic substitution and additions [59], oxidations [59-61], alkylation [62], synthesis of trialkylamines [63], coupling of aryl halides [64], nitration of phenols [65], photoamidation of fluoroolefins [66] and some Diels-Alder reactions. 

Two major types of stabilization mechanisms are described for submicron particles (1) charge stabilization, where surface charge forms a repulsive screen that prevents the particles from flocculation, and (2) steric stabilization, where a surface repulsive screen is formed by solvent-compatible flexible polymeric chains attached to the particle s surface. 

In ultrafiltration, the effluent is passed across a semiper-meable membrane (see Chapter 10). Water passes through the membrane, while submicron particles and large molecules are rejected from the membrane and concentrated. The membrane is supported on a porous medium for strength, as discussed in Chapter 10. Ultrafiltration is used to separate very fine particles (typically in the range 0.001 to 0.02 xm), microorganisms and organic components with molar mass down to 1000 kg kmol. Pressure drops are usually in the range 1.5 to 10 bar. 

James, A. C., Bronchial Deposition of Free Ions and Submicron Particles Studies in Excised Lung, in Infralgfl Particles and. Vapour IV, (W. H. Walton, ed.), pp. 203-219, Pergamon Press, New York (19Y7). 

FIGURE 8.4 Scanning electron micrograph of J774 cells alternatively untreated (A) and treated (B) with cationic lipospheres containing DDAB18. Black arrows indicate internalized submicron particles. Bar corresponds to 10 and 30 4m in panels A and B, respectively. 

The design of a cross-flow filter system employs an inertial filter principle that allows the permeate or filtrate to flow radially through the porous media at a relatively low face velocity compared to that of the mainstream slurry flow in the axial direction, as shown schematically in Figure 15.1.9 Particles entrained in the high-velocity axial flow field are prevented from entering the porous media by the ballistic effect of particle inertia. It has been suggested that submicron particles penetrate the filter medium and form a dynamic membrane or submicron layer, as shown in... 

The variation of iron content in both the slurry and permeate samples against time on stream is represented in Figure 15.14. The permeate purity (in terms of iron concentration) was consistently below 35 ppm (as Fe) for the entire experiment, with over 85% below the 16 ppm level. The variation over iron content could be due to sampling during or after flux maintenance cycles, which can disturb the boundary layer of submicron particles on the membrane surface. 

A variety of techniques are available for sizing particles of pharmaceutical interest. The goal of this chapter is to provide an overview of common techniques currently in use for sizing of powders, and to illustrate their applications. The discussion will focus on techniques used to characterize powders above one micron (jxm) however, it should be emphasized that in some cases the same methods may also be applicable to submicron particles. 

The regional distribution of the DNA adducts in the respiratory tract of diesel exhaust-exposed rats appears to agree with the known deposition pattern of submicron particles, with the highest concentration of adducts in the nasal and the pulmonary tissue (Figure 7) (Bond et al. In Assessment of Inhalation Hazards Integration and Extrapolation Using Diverse Data. 1989, in press). 

Fabrication of composite colloidal spheres involves two steps submicron particles are fabricated from a material preferentially responsive to one class of chemicals followed by a step in which the submicron spheres are coated with a shell that is preferentially responsive to another class of chemicals. A colloidal crystal array is subsequently self-assembled into a 3D ordered film. 

As an example of composite core/shell submicron particles, we made colloidal spheres with a polystyrene core and a silica shell. The polar vapors preferentially affect the silica shell of the composite nanospheres by sorbing into the mesoscale pores of the shell surface. This vapor sorption follows two mechanisms physical adsorption and capillary condensation of condensable vapors17. Similar vapor adsorption mechanisms have been observed in porous silicon20 and colloidal crystal films fabricated from silica submicron particles32, however, with lack of selectivity in vapor response. The nonpolar vapors preferentially affect the properties of the polystyrene core. Sorption of vapors of good solvents for a glassy polymer leads to the increase in polymer free volume and polymer plasticization32. 

Fig. 4.2 TEM images of fabricated nanoparticles, (a) Isolated composite core/shell submicron particles, (b) Hollow silica submicron particles prepared by removing the polystyrene core to demonstrate the high quality of the formed sol gel shell of the composite nanospheres employed to prepare sensing colloidal crystal films...

Fig. 4.3 SEM images of the long range packing assembly of composite colloidal crystal array films assembled on different substrates (a) polycarbonate sheet, (b) Teflon sheet, and (c) Teflon film. The submicron particles were composed of 326 nm diameter polystyrene beads coated with a 20 nm thick Si02 shell. Scale bars in (a c) are 3.00, 3.00, and 2.72 pm, respectively...

P/P0), the colloidal crystal film exhibited an additional increase in the response sensitivity likely due to the swelling of the core of the core/shell submicron particles. This effect was more pronounced upon exposure to toluene. 

The continuous-spray design is ideal for any application in which there is a relatively light loading of submicron particles or condensed organics that form a submicron flame. Ordinarily, the only other piece of equipment applicable to this type of loading would be a high-energy scrubber. Since dust resistivity has no effect on the precipitator, it can be applied successfully on many very difficult dry applications. 

Lespes G, Gigault J. Hyphenated analytical techniques for multidimensional characterisation of submicron particles a review. Anal. Chim. Acta 2011 692 26-41. 

An important application of granulation is in improving the flowability of very fine (submicron) particles which stick together because of the large surface forces acting in materials with very high surface/volume ratios. 

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