Carbonate minerals characteristics

The protocol involving NaOAc-HOAc at pH 5 was first proposed and used by Jackson (1958) to remove carbonates from calcareous soils to analyze soil cation exchange characteristics (Grossman and Millet, 1961). Other researchers used HOAc for the extraction of metals from sediments and soils (Nissenbaum, 1972 Mclaren and Crawford, 1973). Tessier et al. (1979) first used the NaOAc-HOAc solution at pH 5 to dissolve the carbonate fraction from sediments. Since then, the NaOAc-HOAc buffer has been widely used as a specific extractant for the carbonate phase in various media (Tessier et al., 1979 Hickey and Kittrick, 1984 Rapin et al., 1986 Mahan et al., 1987 Han et al., 1992 Clevenger, 1990 Banin et al., 1990). Despite its widespread use, this step is not free from difficulties, and further optimization is required in its application. Questions arise with regard to this step in the elemental extraction from noncalcareous soils, the dissolution capacity and dissolution rates imposed by the buffer at various pHs, and the possibility that different carbonate minerals may require different extraction protocols (Grossman and Millet, 1961 Tessier et al., 1979). 

In the following section we briefly discuss some characteristics of sedimentary carbonate minerals. This discussion provides necessary initial information expanded on in later chapters. 

Abstract. A variety of pyrocarbon/silica gel adsorbents were prepared using commercial mesoporous silica gels Si-40, Si-60, and Si-100 as matrices modified by carbon deposits from pyrolysis of several organic precursors. The second type of hybrid carbon-mineral adsorbents was synthesized using spent natural palygorskite utilized in paraffin purification. The adsorbents were then heated, hydrothermally treated, or modified by additional deposition of carbon. Changes in the structural and adsorption characteristics of hybrid adsorbents before and after treatments were analyzed by microscopy, p-nitrophenol and nitrogen adsorption isotherms, and TG, TEM, XRD, and XRF methods. 

Keywords carbon-mineral adsorbents, pyrolysis, hydrothermal treatment, CCI4 vapors, waste material, utilization, structural characteristics, pore size distribution... 

SYNTHESIS AND STRUCTURAL/ADSORPTION CHARACTERISTICS OF UNMODIFIED AND MODIFIED HYBRID CARBON/MINERAL ADSORBENTS... 

World annual production of natural diamonds, the cubic form of carbon, is about 110 million carats (1 carat = 200 mg). Almost all is derived from kimberlite or its weathered remnants, but Australian production is from the Argyle mine, at which the host rock is lamproite. Kimberlites are olivine- and volatUe-rich potassic ultrabasic rocks of variable geological age that typically form near-vertical carrot-shaped pipes intmded into Archean cratons. The volatile-rich component is predominantly CO2 in the carbonate minerals calcite and dolomite, and the texture is characteristically inequigranular, with large grains (macrocrysts), usually of olivine [Mg2Si04], in a fine-grained, olivine-rich matrix. 

Naturally occurring talc is mined and pulverized before being subjected to flotation processes to remove various impurities such as asbestos (tremolite) carbon dolomite iron oxide and various other magnesium and carbonate minerals. Following this process, the talc is finely powdered, treated with dilute hydrochloric acid, washed with water, and then dried. The processing variables of agglomerated talc strongly influence its physical characteristics. " ... 

For comparison purposes, a sample of Eastern U.S. shale was also analyzed by TG-DTG. The absence of the characteristic carbonate decomposition peak in the 700-800°C temperature range is indicative of the lack of carbonate minerals in Eastern U.S. shales. The net organic pyrolysis yield, 47.6 wt%, Table I, is... 

In terms of this adsorption, properties of various adsorbents, among them the inorganic sorbents can be determined. It must be emphasized that inorganic sorbents such as silica, alumina, titania, complex carbon - mineral sorbents, apatites, e.t.c., are both structurally and energetically heterogeneous. Their total heterogeneity may be described by the kinds of adsorption potential distribution function which is one of the most significant characteristics of the aforementioned solids. 

Besides bulk free water, there are four types of water bound to adsorbents or bio-objects such as strongly (changes in the Gibbs free energy -AG>0.5-1 kJ/mol) and weakly (-AG<0.5-1 kJ/mol) bound and strongly (5h=4-5 ppm) and weakly (5h= 1-2 ppm) associated waters. This boundary value -AG=0.5-1 kJ/mol depends on system composition and the textural characteristics of the materials. At low amounts of adsorbed water (much smaller than the pore volume), typically all water is strongly bound. A portion of this water can be weakly associated if the pore walls are mosaic (partially modified oxides or hybrid carbon-mineral or polymer-mineral systans) and composed with hydrophilic and hydrophobic patches such as partially silylated silica surface. Adsorbed water clusterization depends also on the presence of co-adsorbates such as chloroform, acetonitrile, DMSO, benzene, etc. 

Very early in the history of chemistry many substances were designated as acids, bases, and salts. Acids have a sour taste (e.g., citric acid gives lemon juice its sour taste) they dissolve certain metals and they also dissolve carbonate minerals to produce carbon dioxide. Bases have a bitter taste (e.g., sodium carbonate) they feel slippery when touched and they react with many dissolved metal salts to form precipitates. However, the most striking characteristic of bases is their ability to neutralize the properties of acids when a base reacts with an acid a salt is produced. 

Tannins can also affect the nitrogen and carbon cycles they can complex proteins or metallic ions and can present toxicity for microorganisms and inhibit enzymatic activities. In the majority of studies, mineralization of the nitrogen is decreased by the addition of tannins, while the effects on carbon mineralization remain more variable. By their characteristic link to proteins, tannins inhibit the microbial extracellular enz5mies and can also limit the available substrates for microbial growth. The difference in tannin content of the leaves seems to act on the aquatic macroinvertebrate communities using... 

The thiazolium ring, as most heterocycloammoniums, is a Lewis acid conferring to the carbon atom in the 2-position the carbocationic property of adding the free pair of a base either organic or mineral that may be the molecule of solvent as ROH (Scheme 11). For many nuclei of suitable acidity, these equilibria can be observed in dilute solution by means of absorption spectra when species A and C possess different characteristics (24). For example, benzothiazolium and benzoxazolium in methanol and ethanol give at 10 mole liter 8 and 54% of the alkoxy derivatives for the former and 29 and 90% for the latter respectively. 

Although the black inks are predominantly based on mineral oil, colors are almost entirely formulated with a soya bean oil vehicle. The superior printabHity of colors and economics of blacks guide the selection of product types by the market. Recently developed low mb blacks offer smudge-resistant print. Their share of the market is growing rapidly. The low mb characteristics of these inks are produced through the use of low stmcture carbon black. The addition of resin further enhances the smudge resistance but imposes a premium price. 

AEROPHINE 3418A promoter is widely used ia North and South America, AustraHa, Europe, and Asia for the recovery of copper, lead, and ziac sulfide minerals (see Elotatton). Advantages ia comparison to other collectors (15) are said to be improved selectivity and recoveries ia the treatment of complex ores, higher recoveries of associated precious metals, and a stable grade—recovery relationship which is particularly important to the efficient operation of automated circuits. Additionally, AEROPHINE 3418A is stable and, unlike xanthates (qv), does not form hazardous decomposition products such as carbon disulfide. It is also available blended with other collectors to enhance performance characteristics. 

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