Magnesium hydroxide reactive

Inone S. I., Senna M. Differences between the dissolution and the decomposition kinetics of mechanically activated magnesium hydroxide. Reactivity of Solids 1988 . 5 155-66. 

Upon exposure to the atmosphere, magnesium hydroxide absorbs moisture and carbon dioxide. Reactive grades are converted to the basic carbonate 5MgO 4CO2 XH20 over a period of several years. Grades that resist carbonization at high temperature and humidity have been reported (71). 

Chemica.1 Properties. The reactivity of magnesium hydroxide is measured primarily by specific surface area in units of /g and median particle size in p.m. Reactivity ranges from low, 1-2 /g, 5 p.m, eg, Kyowa s product to high, 60-80 /g, 5—25 pm, eg, Barcroft s CPS and CPS-UF... 

Magnesium hydroxide can also be produced by slaking or pressure hydrating various reactive grades of magnesium oxide. The reaction is highly exothermic (AH gg = —40.86 kJ/mol (—9.77 kcal/mol)) to produce crystalline form at stoichiometric water addition ... 

AH gg = —43.03 kJ/mol ( — 10.28 kcal/mol) including heat of solution, at standard state m = V) and may require a heat sink to prevent boiling of the reaction mixture. A 30% by weight suspension of MgO in 20°C water boils in the absence of any heat sink. The time to reach boiling is dependent on the reactivity of the MgO raw material, and this time can be only several hours for the more reactive grades of MgO. Investigations of the kinetics of formation of magnesium hydroxide by hydration of MgO have been reported (79). 

Dead Seas Periclase Ltd., on the Dead Sea in Israel, uses yet another process to produce magnesium oxide. A concentrated magnesium chloride brine processed from the Dead Sea is sprayed into a reactor at about 1700°C (127,128). The brine is thermally decomposed into magnesium oxide and hydrochloric acid. To further process the magnesia, the product is slaked to form magnesium hydroxide which is then washed, filtered, and calcined under controlled conditions to produce a variety of MgO reactivity grades. A summary of MgO purities, for the various processes is given in Table 20. 

Economic Aspects and Uses. Magnesium hydroxide and magnesium chloride are used as a basic feedstock to make elemental magnesium, MgO refractories, and reactive chemicals. One hundred and sixty thousand tons of magnesium metal were produced ia the United States in 1989 in addition to 1,013,000 tons of MgO equivalent in magnesium compounds (qv) (54). 

Reactive dyes in general are not unusually sensitive to hard water. Nevertheless, the alkali used in most reactive dyeing processes may precipitate calcium or magnesium hydroxide on... 

Crystallization of magnesium hydroxide by a continuous mixed suspension mixed product removal crystallizer was conducted to make clear the characteristics of reactive crystallization kinetics of magnesium hydroxide, which was produced by the precipitation from magnesium chloride with calcium hydroxide. The following operating factors were investigated affecting the crystallization kinetics the initial concentration of feeds, residence time of reactants, feed ratio of reactants, and concentrations of hydroxide and chloride ions. 

The present work deals with the reactive crystallization of magnesium hydroxide, a well-known sparing soluble material, from magnesium chloride with calcium hydroxide. Magnesium hydroxide is produced industrially by the precipitation from brine with... 

Reactive crystallization experiments of magnesium hydroxide were conducted to clarify the characteristics of reactive crystallization kinetics by a continuous MSMPR crystallizer. 

TSUGE MATSUO Reactive CrystaUiZioiion of Magnesium Hydroxide 353... 

Magnesium is a very reactive metal and makes an excellent fuel under the proper conditions. It is oxidized by moist air to form magnesium hydroxide, Mg(OH) 2, and it readily reaets with all acids, including weak species such as vinegar (5% acetic acid) and boric acid. The reactions of magnesium with water and an acid (HX) are shown below ... 

While organo-silane treatments are extensively used in both thermoset and elastomer applications, their use in thermoplastics has so far been somewhat restricted. This is because they do not react with the surface of calcium carbonate, one of the principal fillers used in this type of polymer and because of the lack of a suitable reactive functionality for most of the thermoplastic polymers. Today they are principally used in conjunction with glass fibres, calcined clays, aluminium and magnesium hydroxides, micas and wollastonite. The main thermo-... 

Reactive interfacial agents formed compatibilizer interlayers around nanosize magnesium hydroxide and CNT. 

A variety of furnaces are used in the magnesia industry to calcine either magnesite or magnesium hydroxide filter cake. The most commonly used are the multiple-hearth furnace (MHF) and rotary and shaft kilns. MHFs are primarily used to produce reactive lightly calcined magnesia, while rotary and shaft kilns produce hard and dead-burned grades of magnesia. 

An alternative to the use of magnesium oxide as the additive is to inject magnesium hydroxide into the high temperature zone to provide a highly reactive form of magnesium oxide, i.e. 

Several studies have been done on the reactive crystallization of magnesium hydroxide. Murotani et al.(l) precipitated magnesium hydroxide by adding ammonia to mixed solution of magnesium chloride and ammonium chloride. In this reaction system hexagonal crystals of magnesium hydroxide were obtained... 

It is essential to clarify the crystallization kinetics of magnesium hydroxide and to investigate the influence of various factors on the reactive crystallization characteristics of magnesium hydroxide for better understanding of its crystallization process. The aims of this study are to discuss the followings ... 

Table IV shows the solubilities of various alkali feeds. In general, smaller solubility means that the movement of OH is controlled by ion pair of solute. So it may be difficult for Mg to collide with OH in calcium hydroxide which has the smallest solubility. From SEM photographs of magnesium hydroxide in Figure 3, primary particles are formed in the system of calcium hydroxide, whereas larger primary particles are formed and agglomerated easily in other alkali feed systems which have larger solubility. Then dominant particle size of agglomerated particle becomes larger. Therefore, the solubility may be the key property among the above-mentioned properties. This tendency was also observed in the reactive crystallizations of other carbonates, that is, calcium carbonate(9) and lithium carbonate(lO).

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