Chemical reactivity, mineral-water

Sodium is the most abundant of the alkali metals and is the sixth most abundant element in the Earth s crust, with an abundance of roughly 2.36 wt.%. Owing to its high chemical reactivity with water and, to a lesser extent, with air, sodium metal never occurs free in nature however, the element is ubiquitous and occurs naturally in a wide range of compounds. Sodium chloride is the most common compound of sodium and is dissolved either in seawater or in the crystalline form of halite or rock salt [NaCl, cubic]. However, it is widely present in numerous complex silicates such as feldspars and micas and other nonsilicate minerals such as cryolite [NajAlF, monoclinic], natronite or soda ash [Na COj, mono-clonic], borax [Na B O,. lOH O, monoclinic], sodium hydroxide or caustic soda [NaOH], Chilean saltpeter, and nitratite or soda niter [NaNOj, rhombohedral]. Obviously, the chief ore is the sodium chloride recovered from either brines or rock salt ore deposits. There are... 

Chemical Reactivity - Reactivity with Water No reaction Reactivity with Common Materials Aluminum, copper, brass, lead, zinc salts, mineral acids, oxidizing or reducing agents all can cause rapid decomposition Stability During Transport Unstable, slowly evolves oxygen Inhibitor of Polymerization Not pertinent.. 

Chemical relaxation methods can be used to determine mechanisms of reactions of ions at the mineral/water interface. In this paper, a review of chemical relaxation studies of adsorption/desorption kinetics of inorganic ions at the metal oxide/aqueous interface is presented. Plausible mechanisms based on the triple layer surface complexation model are discussed. Relaxation kinetic studies of the intercalation/ deintercalation of organic and inorganic ions in layered, cage-structured, and channel-structured minerals are also reviewed. In the intercalation studies, plausible mechanisms based on ion-exchange and adsorption/desorption reactions are presented steric and chemical properties of the solute and interlayered compounds are shown to influence the reaction rates. We also discuss the elementary reaction steps which are important in the stereoselective and reactive properties of interlayered compounds. 

A variety of interrelated factors affect the chemical reactivity of mineral surfaces with respect to water and aqueous species, including (1) defect density, (2) cooperative effects among adsorbate molecules, (3) differences in intrinsic properties of different mineral surfaces, including different isoelectric points, (4) solution pH,... 

Potassium does not occur in nature in tlie free state because of its great chemical reactivity. The major basic potash chemical used as a source of potassium is potassium chloride, KC1. The potassium content of all potash sources generally is given in terms of the oxide K2O. The majority of potash produced comes from mineral deposits that were formed by llie evaporation of prehistoric lakes and seas which had become enriched in potassium salts leached from the soil, In addition ro natural deposits of potassium salts, large concentrations of potassium also are found in some bodies of water, including the Great Salt Lake and the Salduro Marsh in Utah, the Dead Sea between Israel and Jordan, and Searles Lake in California. All of these brines are used for the commercial production of potash. 

In the biosphere, vanadium can be considered to be of two forms, one of which is highly mobile, whereas the other is a virtually immobile form. These are closely connected to the oxidation state of vanadium, where the mobile chemically reactive form conforms more or less, but certainly not exclusively, to the V(V) oxidation state. This is the state that vanadium will predominantly have in gas effluents in ash from oil, coal, and gas burners in some minerals and in surface water. Vana-dium(IV) complexes of the types found in minerals will often be relatively immobile but, if subjected to an oxidative environment, can enter the mobile phase in the V(V) oxidation state. Sequestered forms of vanadium can be transported by mechanical processes such as by movements of suspended materials in creeks and rivers, where translocation from terrestrial to lake or marine environments accounts for a high percentage of the movement of vanadium. This procedure does not release the vanadium into the environment in the sense that release from the substrate does rather, the vanadium is simply redeposited as the sediments settle. However, because of the high surface area of the suspended materials, vanadium can efficiently be removed from the suspended material by chemical reactions and enter into the environment as active species by this process. 

Figure 7.38. A schematic representation illustrating the differences between diagenetic processes affecting a carbonate composed of calcite and one composed of a metastable polymineralic assemblage of magnesian calcite, aragonite and calcite. Water-controlled alteration (WCA) processes are driven principally by invasion and evasion of CO2, whereas mineral-controlled alteration (MCA) is mainly governed by the differences in the chemical reactivity of the carbonate minerals. (After James and Choquette, 1984.)...

It is this unpredictable and puzzling chemical reactivity which makes freshly formed silica dust a chemical poison that causes silicosis when it is inhaled. In many processes which deal with mineral products—e.g., the setting of cements, the milling of enamels and of pigments, the slaking of lime, etc.—solids with freshly formed surfaces are brought into contact with water. For understanding these phenomena the kinetics of hydration of incompletely screened surfaces has to be considered. 

The occurrence of highly reactive minerals, such as evaporitic minerals, pyrite and even calcite, in low proportions—a percent or less— in a given rock, e.g., calcareous sandstone, pyritic shale, marl with traces of anhydrite, granite with traces of calcite, may determine the chemical character of stream water (Miller, 1961 Drever, 1988). In a study of 200 streams from monolithologic catchments underlain by various rock types under similar climatic conditions in France, the relative weathering rate based on the cation sum (Meybeck, 1986) ranges from 1 for quartz sandstone to 160 for gypsiferous marl. 

The mineral elements can be held in the coal substance as organo-metallic salts, and also as a result of molecular adsorption and co-valent bonding. The mineral species dissolved in coal pore water, chiefly chlorides can also be considered as part of the inherent matter. The lignites and sub-bituminous coals can have a high fraction of the mineral elements, chiefly sodium, calcium and also aluminium and iron chemically combined in the fuel substance (9,10). The chemical reactivity and porosity of the fuel matrix decrease with the increase of coal age from lignite to bituminous rank. The loss of carboxyl, hydroxyl and quinone bonding sites in the fuel matrix results in a low "chemical" mineral matter content of bituminous coals. 

A linear dependence of the chemical weathering rates on water runoff may be accounted for by deeper percolation of water at high discharge volumes, resulting in a greater contact area with reactive mineral surfaces. 

An impressive property of colloids, including layer silicate minerals, is their large area of reactive surface. Various physical and chemical properties, including water retention and cation exchange capacity, are highly correlated with the surface area of soils. Several techniques estimate the amounts of reactive surface area of soils and are briefly described below. 

Rubidium, an alkali element, was discovered in the mineral water of the Max spring of what is today Bad Diirkheim, Germany, and in the mineral lepidolite (1% Rb). It is a soft, highly reactive metal with a silvery luster, and has chemical properties typical of an alkali metal. The isotopic composition of natural rubidium is 72.15% Rb, a stable isotope, and 27.85% Rb, a (3 emitter. Eighteen artificial isotopes are known (Lenk 2002). Rb changes into Sr. All rubidium salts and rubidium-containing minerals are radioactive and contain Sr, and this natural radioactivity is used for the determination of age in rocks and minerals. 

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