Fine particles chemical composition

The particle size and chemical composition of lead and lead compounds affect the readiness with which lead is absorbed from the lungs and digestive tract (see Lead compounds, industrial toxicology). Larger particles and compounds having low aqueous solubiHty are less hazardous than finely divided particles and compounds of higher solubiHty. 

Clay particles are so finely divided that clay properties are often controlled by the surface properties of the minerals rather than by bulk chemical composition. Particle size, size distribution, and shape the nature and amount of both mineral and organic impurities soluble materials, nature, and amount of exchangeable ions and degree of crystal perfection are all known to affect the properties of clays profoundly. 

When a liquid or solid substance is emitted to the air as particulate matter, its properties and effects may be changed. As a substance is broken up into smaller and smaller particles, more of its surface area is exposed to the air. Under these circumstances, the substance, whatever its chemical composition, tends to combine physically or chemically with other particles or gases in the atmosphere. The resulting combinations are frequently unpredictable. Very small aerosol particles (from 0.001 to 0.1 Im) can act as condensation nuclei to facilitate the condensation of water vapor, thus promoting the formation of fog and ground mist. Particles less than 2 or 3 [Lm in size (about half by weight of the particles suspended in urban air) can penetrate the mucous membrane and attract and convey harmful chemicals such as sulfur dioxide. In order to address the special concerns related to the effects of very fine, iuhalable particulates, EPA replaced its ambient air standards for total suspended particulates (TSP) with standards for particlute matter less than 10 [Lm in size (PM, ). 

The EPMA technique is developed for individual particles of fine-dispersed zeolite powder of various trademarks ZSM-5, ZSM-12, MOR, BEA. The phase and chemical composition of zeolite powder, the surface, shape of particles, stmcture and their distribution in terms of the size were studied using Superprobe-733 device. 

The detailed study of chemical composition, stmcture, surface, shape and sizes of particles of fine-dispersed zeolite powder by EPMA will provide useful recommendations to improve the technology of producing alkanes and alkyl benzenes catalysts. 

Airborne particulate matter, which includes dust, dirt, soot, smoke, and liquid droplets emitted into the air, is small enough to be suspended in the atmosphere. Airborne particulate matter may be a complex mixture of organic and inorganic substances. They can be characterized by their physical attributes, which influence their transport and deposition, and their chemical composition, which influences their effect on health. The physical attributes of airborne particulates include mass concentration and size distribution. Ambient levels of mass concentration are measured in micrograms per cubic meter (mg/m ) size attributes are usually measured in aerodynamic diameter. Particulate matter (PM) exceeding 2.5 microns (/i) in aerodynamic diameter is generally defined as coarse particles, while particles smaller than 2.5 mm (PMj,) are called fine particles. 

Primary clay is also known as residual clay, indicating that they are either the in situ residue of one type of weathered rock or the transported residue of many types of rocks most primary clay deposits occur, however, in situ, at the location where the clay particles were formed. The clay is usually quite pure and colorless or white, but very small relative amounts of minerals mixed with the clay, such as quartz and/or iron oxides, may impart to it a yellow, brown, or green color. Primary clay is also characterized by the extreme fineness of its particles, which usually measure below 2 micrometers (0.002 mm) in diameter. The more than 20 different types of primary clay minerals can be distinguished by their chemical composition, which varies widely, and by their physical properties. Primary clays that have been used for making ceramic objects are listed in Table 55. 

PM causes its health effects, especially its effect on cardiovascular health, are unclear there is some evidence that chemical composition of PM is not as important as particle size, with the greatest risks associated with what is designated as PM 2.5 (particle size less than 2.5 pm). Some experimental evidence suggests (but does not establish) that so-called fine (0.25 to 1.0 pm) and ultrafine (<0.25 pm) are the most potent toxicants, but regulation is now focused on PM 2.5. Regulation of PM and the primary air pollutants is highly contentious, because the costs of controlling them are enormous. 

One hint of possible trouble to come is provided by the information we described in Chapter 4, related to airborne particulate matter (PM). The available evidence ascribes significant increases in the risks of asthma and other respiratory diseases, certain cardiovascular conditions, and lung cancer to PM exposure, particularly those that average less than 2.5 pm (2500 nm) in size. As we noted, the chemical composition of these particles varies widely, depending upon source, but may not be as important as particle size as a risk determinant. Moreover, there is some experimental evidence pointing to the so-called ultra-fines, PM with dimensions below 100 nm, as significant contributors to PM risk. In addition some experimental studies have demonstrated that ultrafines not only distribute themselves throughout the airways, but seem to be able to translocate to other parts of the body - liver, heart, perhaps the CNS. 

The chemical and physical aspects of crud can dilfer for each separate operation and will vary in inorganic composition, organic content, color, and density. The composition of many cruds appears to have in common such constituents as Si, Al, Fe, P, SO4, particles of gypsum, clay, and other fine particles together with the solvent. Often there is a direct relation between the feed liquor and the crud compositions, indicating possible aqueous carryover as well as inefficient clarification before solvent extraction [33]. Various researchers have reported on the formation of crud and its characterization in their circuits [42-45]. 

The size and morphology are characteristic parameters of metal particles. It is possible to determine them by various techniques transmission electron microscopy (TEM) [105-107], X-ray photoelectron spectroscopy (XPS) [108], X-ray diffraction (XRD), extended X-ray absorption fine structure (EXAES) [109, 110], thermoprogrammed oxidation, reduction or desorption (TPO, TPR or TPO) and chemisorption of probe molecules (H2, O2, CO, NO) are currently used. It is therefore possible to know the particles (i) size (by TEM) [105-107], extended X-ray absorption fine structure (EXAES) [109, 110]), (ii) structure (by XRD, TEM), (iii) chemical composition (by TEM-EDAX, elemental analysis), (iv) chemical state (surface and bulk metal atoms by XPS [108], TPD, TPR, TPO) and... 

In order to avoid the use of lead compounds on environmental grounds, lithium fluoride (liF) has been chosen to obtain super-rate burning of nitramine composite propellants.P7281 Typical chemical compositions of HMX composite propellants-with and without liF are shown in Table 7.4. The non-catalyzed HMX propellant is used as a reference pyrolant to evaluate the effect of super-rate burning. The HMX particles are of finely divided, crystalline (3-HMX with a bimodal size distribution. Hydroxy-terminated polyether (HTPE) is used as a binder, the OH groups of which are cured with isophorone diisocyanate. The chemical properties of the HTPE binder are summarized in Table 7.5. 

This result may be deceptive, however, as we had to eliminate the many studies from Cols. 2 and 3 that contained no size Information, so the two sets of averages are not for the same populations of plants. A further problem with these data may also be the Inclusion of particles up to 2.5-pm dlam, whereas, recent studies (44, 46) indicate that the large changes of composition occur below about 0.5-pm dlam. Thus, our "fine" particles In Table IV Include particulate mass between 0.5 and 2.5 ym that Is chemically similar to larger particles, which reduces the Rvalues. We made the cut at 2.5 ym to develop components for separate CEBs of fine and coarse particles In ambient air, which are commonly divided at about that point. 

Improved control devices now frequently installed on conventional coal-utility boilers drastically affect the quantity, chemical composition, and physical characteristics of fine-particles emitted to the atmosphere from these sources. We recently sampled fly-ash aerosols upstream and downstream from a modern lime-slurry, spray-tower system installed on a 430-Mw(e) coal utility boiler. Particulate samples were collected in situ on membrane filters and in University of Washington MKIII and MKV cascade impactors. The MKV impactor, operated at reduced pressure and with a cyclone preseparator, provided 13 discrete particle-size fractions with median diameters ranging from 0,07 to 20 pm with up to 6 of the fractions in the highly respirable submicron particle range. The concentrations of up to 35 elements and estimates of the size distributions of particles in each of the fly-ash fractions were determined by instrumental neutron activation analysis and by electron microscopy, respectively. Mechanisms of fine-particle formation and chemical enrichment in the flue-gas desulfurization system are discussed. 

Wolff, G. T., M. A. Ferrnan, N. A. Kelley, D. P. Stroup, and M. S. Ruthkosky, The Relationships between the Chemical Composition of Fine Particles and Visibility in the Detroit Metropolitan Area, J. Air Pollut. Control Assoc., 32, 1216-1220 (1982a). 

The chemical composition of particles collected in the museums was also compared to that outdoors using a mass balance model. The results indicated that there were significant indoor sources of fine particle organics and that this source(s) was a significant fraction of the total indoor fine particle organic concentration (Ligocki et al., 1993). A similar conclusion was reached by Naik et al. (1991) in measurements made in a telephone... 

Some degree of fractionation as function of distance from the power station smoke stack is to be expected coarse particles will fall out in the immediate vicinity of the power station, whereas fine fly ash will be transported further, and gaseous emissions might be expected to be transported the furthest. Thus, from the point of view of environmental health, not only the chemical composition of emitted particles and aerosols, but also their size, is relevant (Teinemaa et al. 2002). As particulate matter is dominated by basic oxides (e.g., CaO) and gaseous emissions by acidic gases (e.g., CO2, SO2), this fractionation will influence the pH of... 

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