Synthetic magnesium silicate

Last updated

Synthetic magnesium silicates are white, odorless, finely divided powders formed by the precipitation reaction of water-soluble sodium silicate (water glass) and a water-soluble magnesium salt such as magnesium chloride, magnesium nitrate or magnesium sulfate. The composition of the precipitate depends on the ratio of the components in the reaction medium, the addition of the correcting substances, and the way in which they are precipitated. [1] [2] [3]

Contents

The molecular formula is typically written as MgO:XSiO2, where X denotes the average mole ratio of SiO2 to MgO. The product is hydrated and the formula is sometimes written MgO:XSiO2•H2O to show the water of hydration.

Properties

Unlike natural magnesium silicates like talc, forsterite, and olivine which are crystalline, synthetic magnesium silicates are amorphous. [1] Synthetic magnesium silicates are insoluble in water or alcohol. [4] The particles are usually porous, and the BET surface area can range from less than 100 m2/g to several hundred m2/g.

Applications

The very large active surface makes synthetic magnesium silicate useful for a wide variety of applications: purifying adsorbent (polyols, animal and vegetable oils, chromatography, [5] dry cleaning, sugar, resins, odors); filler (rubber, ceramics, paper, glass, refractories); anti-caking agent (salt); catalyst; catalyst carrier; filter medium. [4]

In food

The U.S. Food Chemicals Codex, [6] JECFA, [7] and other monographs for Food Grade synthetic magnesium silicate specify a mole ratio of 2MgO:5SiO2 (or X=2.5 in the general formula). The most common use for Food Grade synthetic magnesium silicate is as an active filter aid for adsorption of color, free fatty acids and other polar compounds from used frying oils. [8] [9] Various national and international regulations allow use of this material as an anti-caking agent in a wide variety of powdered foods. [10] [11] [12] [13]

When used as a food additive, it is safe to ingest synthetic magnesium silicate. In 1990, the safety of synthetic magnesium silicate was reviewed by the Scientific Committee on Food (SCF) together with that of silica and the other metal alkali silicates. [10] The SCF noted that “the available data, including a number of short-term studies in two species, appear to substantiate the biological inertness of those compounds”. The SCF established a group Acceptable Daily Intake (ADI) not specified for silicon dioxide and the alkali metal silicates.

See also

Related Research Articles

<span class="mw-page-title-main">Mineral</span> Crystalline chemical element or compound formed by geologic processes

In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid substance with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.

<span class="mw-page-title-main">Talc</span> Hydrated magnesium phyllosilicate mineral

Talc, or talcum, is a clay mineral, composed of hydrated magnesium silicate with the chemical formula Mg3Si4O10(OH)2. Talc in powdered form, often combined with corn starch, is used as baby powder. This mineral is used as a thickening agent and lubricant. It is an ingredient in ceramics, paints, and roofing material. It is a main ingredient in many cosmetics. It occurs as foliated to fibrous masses, and in an exceptionally rare crystal form. It has a perfect basal cleavage and an uneven flat fracture, and it is foliated with a two-dimensional platy form.

<span class="mw-page-title-main">Silicon dioxide</span> Oxide of silicon

Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula SiO2, most commonly found in nature as quartz. In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and most abundant families of materials, existing as a compound of several minerals and as a synthetic product. Notable examples include fused quartz, fumed silica, silica gel, opal and aerogels. It is used in structural materials, microelectronics, and as components in the food and pharmaceutical industries.

<span class="mw-page-title-main">Silica gel</span> Chemical compound

Silica gel is an amorphous and porous form of silicon dioxide (silica), consisting of an irregular tridimensional framework of alternating silicon and oxygen atoms with nanometer-scale voids and pores. The voids may contain water or some other liquids, or may be filled by gas or vacuum. In the last case, the material is properly called silica xerogel.

<span class="mw-page-title-main">Sodium silicate</span> Hygroscopic chemical compound of variable Na2O/SiO2 ratio precursor of waterglass

Sodium silicate is a generic name for chemical compounds with the formula Na
2xSi
yO
2y+x or (Na
2O)
x·(SiO
2)
y, such as sodium metasilicate Na
2SiO
3, sodium orthosilicate Na
4SiO
4, and sodium pyrosilicate Na
6Si
2O
7. The anions are often polymeric. These compounds are generally colorless transparent solids or white powders, and soluble in water in various amounts.

The Bayer process is the principal industrial means of refining bauxite to produce alumina (aluminium oxide) and was developed by Carl Josef Bayer. Bauxite, the most important ore of aluminium, contains only 30–60% aluminium oxide (Al2O3), the rest being a mixture of silica, various iron oxides, and titanium dioxide. The aluminium oxide must be further purified before it can be refined into aluminium metal.

<span class="mw-page-title-main">Magnesium carbonate</span> Chemical compound

Magnesium carbonate, MgCO3, is an inorganic salt that is a colourless or white solid. Several hydrated and basic forms of magnesium carbonate also exist as minerals.

Calcium silicate is the chemical compound Ca2SiO4, also known as calcium orthosilicate and is sometimes formulated as 2CaO·SiO2. It is also referred to by the shortened trade name Cal-Sil or Calsil. It occurs naturally as the mineral larnite.

Cement chemist notation (CCN) was developed to simplify the formulas cement chemists use on a daily basis. It is a shorthand way of writing the chemical formula of oxides of calcium, silicon, and various metals.

An anticaking agent is an additive placed in powdered or granulated materials, such as table salt or confectioneries, to prevent the formation of lumps (caking) and for easing packaging, transport, flowability, and consumption. Caking mechanisms depend on the nature of the material. Crystalline solids often cake by formation of liquid bridge and subsequent fusion of microcrystals. Amorphous materials can cake by glass transitions and changes in viscosity. Polymorphic phase transitions can also induce caking.

<span class="mw-page-title-main">Biogenic silica</span> Type of biogenic mineral

Biogenic silica (bSi), also referred to as opal, biogenic opal, or amorphous opaline silica, forms one of the most widespread biogenic minerals. For example, microscopic particles of silica called phytoliths can be found in grasses and other plants.

<span class="mw-page-title-main">Hexafluorosilicic acid</span> Octahedric silicon compound

Hexafluorosilicic acid is an inorganic compound with the chemical formula H
2SiF
6. Aqueous solutions of hexafluorosilicic acid consist of salts of the cation and hexafluorosilicate anion. These salts and their aqueous solutions are colorless.

The calc-alkaline magma series is one of two main subdivisions of the subalkaline magma series, the other subalkaline magma series being the tholeiitic series. A magma series is a series of compositions that describes the evolution of a mafic magma, which is high in magnesium and iron and produces basalt or gabbro, as it fractionally crystallizes to become a felsic magma, which is low in magnesium and iron and produces rhyolite or granite. Calc-alkaline rocks are rich in alkaline earths and alkali metals and make up a major part of the crust of the continents.

<span class="mw-page-title-main">Alkali soil</span> Soil type with pH > 8.5

Alkali, or Alkaline, soils are clay soils with high pH, a poor soil structure and a low infiltration capacity. Often they have a hard calcareous layer at 0.5 to 1 metre depth. Alkali soils owe their unfavorable physico-chemical properties mainly to the dominating presence of sodium carbonate, which causes the soil to swell and difficult to clarify/settle. They derive their name from the alkali metal group of elements, to which sodium belongs, and which can induce basicity. Sometimes these soils are also referred to as alkaline sodic soils.
Alkaline soils are basic, but not all basic soils are alkaline.

<span class="mw-page-title-main">Alkali–silica reaction</span> Chemical reaction damaging concrete

The alkali–silica reaction (ASR), more commonly known as concrete cancer, is a deleterious swelling reaction that occurs over time in concrete between the highly alkaline cement paste and the reactive amorphous silica found in many common aggregates, given sufficient moisture.

<span class="mw-page-title-main">Hydrated silica</span> Chemical compound

Hydrated silica is a form of silicon dioxide, which has a variable amount of water in the formula. When dissolved in water, it is usually known as silicic acid. It is found in nature as opal, and in the cell walls of diatoms. It is also synthetically manufactured for use in toothpaste as an abrasive to assist in cleaning. Hydrated silica can be dehydrated to produce silica gel, which is used as a desiccant. It is also used in various paints and varnishes and in the production of beer.

Precipitated silica is an amorphous form of silica (silicon dioxide, SiO2); it is a white, powdery material. Precipitated silica is produced by precipitation from a solution containing silicate salts.

<span class="mw-page-title-main">Concrete degradation</span> Damage to concrete affecting its mechanical strength and its durability

Concrete degradation may have many different causes. Concrete is mostly damaged by the corrosion of reinforcement bars due to the carbonatation of hardened cement paste or chloride attack under wet conditions. Chemical damages are caused by the formation of expansive products produced by various chemical reactions, by aggressive chemical species present in groundwater and seawater, or by microorganisms. Other damaging processes can also involve calcium leaching by water infiltration and different physical phenomena initiating cracks formation and propagation. All these detrimental processes and damaging agents adversely affects the concrete mechanical strength and its durability.

The purpose of a mineralizer is to facilitate the transport of insoluble “nutrient” to a seed crystal by means of a reversible chemical reaction. Over time, the seed crystal accumulates the material that was once in the nutrient and grows. Mineralizers are additives that aid the solubilization of the nutrient solid. When used in small quantities, mineralizers function as catalysts. Typically, a more stable solid is crystallized from a solution that consists of a less stable solid and a solvent. The process is done by dissolution-precipitation or crystallization process.

The pozzolanic activity is a measure for the degree of reaction over time or the reaction rate between a pozzolan and Ca2+ or calcium hydroxide (Ca(OH)2) in the presence of water. The rate of the pozzolanic reaction is dependent on the intrinsic characteristics of the pozzolan such as the specific surface area, the chemical composition and the active phase content.

References

  1. 1 2 Ralph K. Iler, The Chemistry of Silica: Solubility, Polymerization, Colloid, and Surface Properties, and Biochemistry, John Wiley and Sons (1979)
  2. ↑ Krysztafkiewics, A., Lipska, L.K., Ciesielczyk, F., and Jesionowski, T. Amorphous magnesium silicate – synthesis, physicochemical properties and surface morphology. Advanced Powder Technol, 15, 549, 2004.
  3. ↑ Ciesielczyk, F., Krysztafkiewics, A., Jesionowski, T. Physicochemical studies on precipitated magnesium silicates. J Mater Sci. 42, 3831, 2007.
  4. 1 2 Condensed Chemical Dictionary, Eleventh Edition, Van Nostrand and Reinhold Co. Inc., New York, NY (1987)
  5. ↑ U.S. Silica, FLORISIL®
  6. ↑ Food Chemicals Codex, Seventh Edition, United Book Press Inc., Baltimore, MD (2010)
  7. ↑ Food and Agricultural Organization of the United Nations/World Health Organization Joint Expert Committee on Food Additives, 61st Session, published in NFP 52, Add 11, 2003.
  8. ↑ ACE Filters International; Miracle FP
  9. ↑ Michael D. Erickson (Editor), Deep Frying: Chemistry, Nutrition, and Practical Applications, 2ND Edition, AOCS Press (2007)
  10. 1 2 Codex Alimentarius General Standard for Food Additives, Codex Alimentarius, Volume 1, General Requirements, 1991
  11. ↑ 21 CFR 182.2437, U.S. Code of Federal Regulations
  12. ↑ European Union Commission Directive 2008/84/EC of 27 August 2008
  13. ↑ No. 98-90, Korea Food and Drug Administration Bulletin
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.