Bentonite

Rock type or absorbent swelling clay

Link to taotaohui

Not to be confused with the Ba,Ca,Mg-mixed carbonate mineral Benstonite

For the chromium-rich ettringite mineral, see Bentorite

For the barium titanium cyclosilicate mineral, see benitoite

Bentonite layers from an ancient deposit of weathered volcanic ash tuff in Wyoming Gray shale and bentonites (Benton Shale; Colorado Springs, Colorado)

Bentonite ( BEN-tə-nyte)[1][2] is an absorbent swelling clay consisting mostly of montmorillonite (a type of smectite) which can either be Na-montmorillonite or Ca-montmorillonite. Na-montmorillonite has a considerably greater swelling capacity than Ca-montmorillonite.

Bentonite usually forms from the weathering of volcanic ash in seawater, or by hydrothermal circulation through the porosity of volcanic ash beds,[3][4] which converts (devitrification) the volcanic glass (obsidian, rhyolite, dacite) present in the ash into clay minerals. In the mineral alteration process, a large fraction (up to 40&#;50 wt.%) of amorphous silica is dissolved and leached away, leaving the bentonite deposit in place.[citation needed] Bentonite beds are white or pale blue or green (traces of reduced Fe2+
) in fresh exposures, turning to a cream color and then yellow, red, or brown (traces of oxidized Fe3+
) as the exposure is weathered further.[5]

As a swelling clay, bentonite has the ability to absorb large quantities of water, which increases its volume by up to a factor of eight.[5] This makes bentonite beds unsuitable for building and road construction. However, the swelling property is used to advantage in drilling mud and groundwater sealants. The montmorillonite / smectite making up bentonite is an aluminium phyllosilicate mineral, which takes the form of microscopic platy grains. These give the clay a very large total surface area, making bentonite a valuable adsorbent. The plates also adhere to each other when wet. This gives the clay a cohesiveness that makes it useful as a binder and as an additive to improve the plasticity of kaolinite clay used for pottery.

One of the first findings of bentonite was in the Cretaceous Benton Shale near Rock River, Wyoming. The Fort Benton Group, along with others in stratigraphic succession, was named after Fort Benton, Montana, in the mid-19th century by Fielding Bradford Meek and F. V. Hayden of the U.S. Geological Survey.[4] Bentonite has since been found in many other locations, including China and Greece (bentonite deposit of the Milos volcanic island in the Aegean Sea). The total worldwide production of bentonite in was 20,400,000 metric tons.[7]

Types

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2:1 clay minerals crystallographic structure made of three superimposed sheets of Tetrahedra-Octahedra-Tetrahedra (TOT layer unit), respectively Detailed molecular structure of pure montmorillonite, the best known end-member of the smectite group. The interlayer space between two successive TOT layers is filled with hydrated cations (mainly

Na

+

and

Ca

2+

ions) compensating the negative electrical charges of the TOT layers and with water molecules causing the interlayer expansion.

In geology, the term bentonite is applied to a type of claystone (a clay rock, not a clay mineral) composed mostly of montmorillonite (a clay mineral from the smectite group). It forms by devitrification of volcanic ash or tuff,[5] typically in a marine environment.[3][4] This results in a very soft, porous rock that may contain residual crystals of more resistant minerals, and which feels soapy or greasy to the touch. However, in commercial and industrial applications, the term bentonite is used more generally to refer to any swelling clay composed mostly of smectite clay minerals, which includes montmorillonite.[5] The undifferentiated reference to the weathered volcanic rock for the geologist or to the industrial mixture of swelling clays can be a source of confusion.

The montmorillonite making up bentonite is an aluminium phyllosilicate mineral whose crystal structure is described as low-charge TOT. This means that a crystal of montmorillonite consists of layers, each of which is made up of two T sheets bonded to either side of an O sheet. The T sheets are so called because each aluminium or silicon ion in the sheet is surrounded by four oxygen ions arranged as a tetrahedron. The O sheets are so called because each aluminium ion is surrounded by six oxygen or hydroxyl ions arranged as an octahedron. The complete TOT layer has a weak negative electrical charge, and this is neutralized by calcium or sodium cations that bind adjacent layers together, with a distance between layers of about 1 nanometer. Because the negative charge is weak, only a fraction of the possible cation sites on the surface of a TOT layer actually contain calcium or sodium. Water molecules can easily infiltrate between sheets and fill the remaining sites. This accounts for the swelling property of montmorillonite and other smectite clay minerals.

The different types of bentonite are each named after the respective dominant cation.[8] For industrial purposes, two main classes of bentonite are recognized: sodium and calcium bentonite. Sodium bentonite is the more valuable but calcium bentonite is more common.[7] In stratigraphy and tephrochronology, completely devitrified (weathered volcanic glass) ash-fall beds are sometimes also referred to as "K-bentonites" (the illitized clay rock) when the dominant clay species is illite (a non-swelling clay).[9] However, in pure clay mineralogy, the term illite is more appropriate than "K-bentonite" (the "altered K-rock") because it is a distinct type of non-swelling clay while the commercial term bentonite implicitly refers to a swelling clay, a smectite (in the European and UK terminology), or a montmorillonite (in the US terminology).

Sodium bentonite

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Sodium bentonite expands when wet, absorbing as much as several times its dry mass in water. Because of its excellent colloidal properties,[10] it is often used in drilling mud for oil and gas wells and boreholes for geotechnical and environmental investigations.[11] The property of swelling also makes sodium bentonite useful as a sealant, since it provides a self-sealing, low permeability barrier. It is used to line the base of landfills, for example. Bentonite is also part of the backfill material used at the nuclear Waste Isolation Pilot Project.[12] Various surface modifications to sodium bentonite improve some rheological or sealing performance in geoenvironmental applications, for example, the addition of polymers.[13]

Sodium bentonite can be combined with elemental sulfur as fertilizer prills. These permit slow oxidation of the sulfur to sulfate, a plant nutrient needed for some crops like onions or garlic synthesizing a lot of organo-sulfur compounds, and maintain sulfate levels in rainfall-leached soil longer than either pure powdered sulfur or gypsum.[14] Sulfur/bentonite pads with added organic fertilizers have been used for organic farming.[15]

Calcium bentonite

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Calcium bentonite is a useful adsorbent of ions in solution,[16] as well as fats and oils. It is the main active ingredient of fuller's earth, probably one of the earliest industrial cleaning agents.[17] It has significantly less swelling capacity than sodium bentonite.[18]

Calcium bentonite may be converted to sodium bentonite (termed sodium beneficiation or sodium activation) to exhibit many of sodium bentonite's properties by an ion exchange process. As commonly practiced, this means adding 5&#;10% of a soluble sodium salt such as sodium carbonate to wet bentonite, mixing well, and allowing time for the ion exchange to take place and water to remove the exchanged calcium.[19][20] Some properties, such as viscosity and fluid loss of suspensions, of sodium-beneficiated calcium bentonite (or sodium-activated bentonite) may not be fully equivalent to those of natural sodium bentonite.[10] For example, residual calcium carbonates (formed if exchanged cations are insufficiently removed) may result in inferior performance of the bentonite in geosynthetic liners.[21]

Illitisation of smectite clays by potassium ions and K-bentonite rock

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Illite is the main clay constituent of potash bentonite (a rock type also known as K-bentonite or potassium bentonite). K-bentonite is a term reserved to volcanic stratigraphy and tephrochronology and is related to the weathered clay rock type only. Illite, the clay mineral, is a potassium-rich phyllosilicate formed from the alteration of smectic clay in contact with groundwater rich in K+
ions.[9] Illite is a high-charge TOT clay mineral, in which negatively charged sheets are bound relatively strongly by more numerous potassium cations, and so it is no longer a swelling clay and has few industrial uses. In contrast to the highly hydrated Na+
ions which act as "swellers" or "expanders" ions, poorly hydrated K+
ions behave as "collapsers" when exchanging with Na+
ions accessible in the interlayers space present between two TOT layers. Dehydrated K+
ions are preferentially located in between two face-to-face hexagonal cavities formed by six joined silica tetrahedra present at the surface of the basal plane of a TOT layer (see the corresponding figure showing an elementary TOT layer). Because dehydrated, these K+
ions are sometimes said to form inner-sphere bonds with the surrounding oxygen atoms present in the hexagonal cavity hosting them. It means there is no water molecule in between the K+
ion and the oxygen atoms attached to the silica tetrahedra (T).

Applications

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Making a bentonite slurry for fining after wine pressing

The main uses of bentonite are in drilling mud and as a binder, purifier, absorbent, and carrier for fertilizers or pesticides. As of around , almost half of the US production of bentonite was used as drilling mud. Minor uses include filler, sealant, and catalyst in petroleum refining. Calcium bentonite is sometimes marketed as fuller's earth, whose uses overlap with those of other forms of bentonite.[11][23]

Drilling mud

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Bentonite is used in drilling mud to lubricate and cool the cutting tools (drill bit), to remove cuttings, to stabilize the borehole walls, and to help prevent blowouts (by maintaining a sufficient hydraulic pressure in the well). Bentonite also curtails drilling fluid invasion by its propensity for aiding in the formation of mud cake.[11] It plays an important role in the earth pressure balance and slurry shield variants of tunnel boring machines.

Much of bentonite's usefulness in the drilling and geotechnical engineering industry comes from its unique rheological properties. Relatively small quantities of bentonite suspended in water form a viscous, shear-thinning material. Most often, bentonite suspensions are also thixotropic,[24] although rare cases of rheopectic behavior have also been reported.[25] At high enough concentrations (about 60 grams of bentonite per litre of suspension, ~6wt.%), bentonite suspensions begin to take on the characteristics of a gel (a fluid with a minimum yield strength required to make it move).[24]

Binder

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Bentonite has been widely used as a foundry-sand bond in iron and steel foundries. Sodium bentonite is most commonly used for large castings that use dry molds, while calcium bentonite is more commonly used for smaller castings that use "green" or wet molds. Bentonite is also used as a binding agent in the manufacture of iron ore (taconite) pellets as used in the steelmaking industry.[11] Bentonite, in small percentages, is used as an ingredient in commercial and homemade clay bodies and ceramic glazes. It greatly increases the plasticity of clay bodies and decreases settling in glazes, making both easier to work with for most applications.[26][27]

The ionic surface of bentonite has a useful property in making a sticky coating on sand grains. When a small proportion of finely ground bentonite clay is added to hard sand and wetted, the clay binds the sand particles into a moldable aggregate known as green sand used for making molds in sand casting.[28] Some river deltas naturally deposit just such a blend of clay silt and sand, creating a natural source of excellent molding sand that was critical to ancient metalworking technology. Modern chemical processes to modify the ionic surface of bentonite greatly intensify this stickiness, resulting in remarkably dough-like yet strong casting sand mixes that stand up to molten metal temperatures.[citation needed]

The same effluvial deposition of bentonite clay onto beaches accounts for the variety of plasticity of sand from place to place for building sand castles. Beach sand consisting of only silica and shell grains does not mold well compared to grains coated with bentonite clay. This is why some beaches are much better for building sandcastles than others.[citation needed]

The self-stickiness of bentonite allows high-pressure ramming or pressing of the clay in molds to produce hard, refractory shapes, such as model rocket nozzles.[29]

Purification

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Bentonites are used for decolorizing various mineral, vegetable, and animal oils. They are also used for clarifying wine, liquor, cider, beer, mead, and vinegar.[11]

Bentonite has the property of adsorbing relatively large amounts of protein molecules from aqueous solutions. Consequently, bentonite is uniquely useful in the process of winemaking, where it is used to remove excessive amounts of protein from white wines. Were it not for this use of bentonite, many or most white wines would precipitate undesirable flocculent clouds or hazes upon exposure to warm temperatures, as these proteins denature. It also has the incidental use of inducing more rapid clarification of both red and white wines.[30]

Bentonite is also considered an effective low-cost adsorbent for the removal of chromium(VI) ions from aqueous solutions (contaminated wastewater).[31]

Absorbent

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Bentonite is used in a variety of pet care items such as cat litter to absorb pet waste. It is also used to absorb oils and grease.[11]

Carrier

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Bentonite is used as an inert carrier for pesticides, fertilizers, and fire retardants. It helps ensure that the active agent is uniformly dispersed and that pesticides and fertilizers are retained on the plants.[11]

Filler

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Bentonite is used as a filler in a wide variety of products, including adhesives, cosmetics, paint, rubber, and soaps. It also acts as a stabilizer and extender in these products.[11]

Sealant

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The property of swelling on contact with water makes sodium bentonite useful as a sealant since it provides a self-sealing, low-permeability barrier. It is used to line the base of landfills to prevent migration of leachate, for confining metal pollutants of groundwater, and for the sealing of subsurface disposal systems for spent nuclear fuel.[32] Similar uses include making slurry walls, waterproofing of below-grade walls, and forming other impermeable barriers, e.g., to seal off the annulus of a water well, to plug old wells.

Bentonite can also be "sandwiched" between synthetic materials to create geosynthetic clay liners (GCLs) for the aforementioned purposes. This technique allows for more convenient transport and installation, and it greatly reduces the volume of bentonite required. It is also used to form barriers around newly planted trees to constrain the growth of its roots: in order to prevent damage to any of the nearby footpaths, parking lots, playgrounds, etc; or any of the surrounding underground infrastructures like the pipes, drainage systems, sewers, etc. Farmers use bentonite to seal retention ponds and line canals.[33]

Catalyst

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High-purity calcium bentonite is treated with acid for use as a catalyst in cracking heavy petroleum fractions.[11]

Medicine

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Bentonite has been prescribed as a bulk laxative, and it is also used as a base for many dermatologic formulas.[34] Granular bentonite is being studied for use in battlefield wound dressings.[35] Bentonite is also sold online and in retail outlets for a variety of indications.[36]

If you are looking for more details, kindly visit Bulk Granular Bentonite Cat Litter.

Bentoquatam is a bentonate-based topical medication intended to act as a shield against exposure to urushiol, the oil found in plants such as poison ivy or poison oak.[37]

Bentonite can also be used as a desiccant due to its adsorption properties. Bentonite desiccants have been successfully used to protect pharmaceutical, nutraceutical, and diagnostic products from moisture degradation and extend shelf life. In most common package environments, bentonite desiccants offer a higher water adsorption capacity than silica gel desiccants. Bentonite complies with the FDA for contact with food and drugs.[38]

Farming in Thailand

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The application of clay technology by farmers in northeast Thailand, using bentonite clay, has dramatically reversed soil degradation and resulted in greater economic returns, with higher yields and higher output prices. Studies carried out by The International Water Management Institute and partners in &#; focused on the application of locally sourced bentonite clays to degraded soils in the region. These applications were carried out in structured field trials. Applying bentonite clays effectively improved yields of forage sorghum grown under rain-fed conditions.[39][40]

Bentonite application also influenced the prices that farmers received for their crops. Production costs are higher, but due to higher production and the quality of the food, clay farmers could afford to invest and grow more and better food, compared to nonclay-using farmers.[41][42]

Bentonite slurry walls in modern construction

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Bentonite slurry walls (also known as diaphragm walls [43] ) are used in construction, where the slurry wall is a trench filled with a thick colloidal mixture of bentonite and water.[44] A trench that would collapse due to the hydraulic pressure in the surrounding soil does not collapse as the slurry balances the hydraulic pressure. Forms for concrete, and rebar, can be assembled in a slurry-filled trench, and then have concrete poured into the form. The liquid concrete being denser displaces the less-dense bentonite slurry and causes the latter to overflow from the trench. This displaced bentonite slurry is then channeled to a recycling unit from which it can subsequently be reused in a new trench elsewhere on the construction site.

In addition, because the colloid is relatively impervious to water, a slurry wall can prevent the seepage of groundwater, which is useful in preventing the further spread of groundwater that has been contaminated by toxic material such as industrial waste.[44]

Ceramics

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Plasticity is the property of clay that allows it to be manipulated and retain its shape without cracking after the shaping force has been removed; clays with low plasticity are known as short or non-plastic. A small amount of bentonite added to clay can increase its plasticity, and hence ease forming of articles by some shaping techniques. However, bentonite typically contains minerals that affect the fired color of the mix,[26] and its swelling properties can make such a mix prone to significant shrinkage and potential cracking as it dries.[45]

Ceramic glazes often contain bentonite. The bentonite is added to slow or prevent the settling of the glazes. It can also improve the consistency of application of glazes on porous biscuit-fired ware. Once a certain amount of glaze water has been absorbed by the biscuit the bentonite effectively clogs the pores and resists the absorption of further water resulting in a more evenly thick coat.[27]

Emergency response

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Bentonite is used in industry and emergency response as a chemical absorbent and container sealant.

History and natural occurrence

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In , China was the top producer of bentonite, with almost a one-quarter share of the world's production, followed by the United States and India. Total worldwide production was 24,400,000 metric tons of bentonite and 3,400,000 metric tons of fuller's earth.[46][7]

Most high-grade natural sodium bentonite is produced from the western United States in an area between the Black Hills of South Dakota and the Bighorn Basin of Wyoming, and the Tokat Resadiye region of Turkey.[11] Mixed sodium/calcium bentonite is mined in Greece, Pakistan, Australia, India, Russia, and Ukraine.

In the United States, calcium bentonite is mined primarily in Mississippi and Alabama.[11] Other major locations producing calcium bentonite include New Zealand, Germany, Greece, Turkey, India, and China.

See also

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• Medicinal clay &#; Use of clay for health reasons

References

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Die Erfindung betrifft ein hochporöses Granulat zur Ad- bzw. Absorption von Flüssigkeiten und Gasen, insbesondere zur Verwendung als Hygiene-Tierstreu.The invention relates to a highly porous granulate for ad- or Absorption of liquids and gases, especially for Use as hygienic animal litter.

Für den stetig wachsenden Bedarf an ad- bzw. absorptionsfähigen Materialien zur Verwendung als Tierstreu sind diverse Produkte zur Aufnahme von flüssigen und/oder festen Exkrementen im Handel.For the constantly growing need for ad or absorbent materials for use as animal litter are various products for the absorption of liquid and / or fixed excrement in trade.

Bei den bekannten Tierstreu-Produkten handelt es sich im wesentlichen um Produkte auf Basis von Tonmineralen, wie Sepiolite, Attapulgite, Bentonite, oder synthetisch hergestellte mikroporige Calciumsilikate, Gasbeton-Abfälle oder porosiertem gebrannten Ton. Sie werden in Körnungen zwischen 0,5 oder 6 mm fraktioniert angeboten. Mit Ausnahme von Bentonit sind diese Produkte überwiegend von kompakter, steinartiger Konsistenz. Ein erhebliches Problem stellt hierbei die Entsorgung dar, weil diese Streumaterialien nur schwer oder überhaupt nicht verwittern bzw. verrotten.The well-known animal litter products are in essential to products based on clay minerals, such as Sepiolite, Attapulgite, Bentonite, or synthetic manufactured microporous calcium silicates, gas concrete waste or porous fired clay. They are in grits offered between 0.5 or 6 mm in fractions. With the exception Bentonite products are mostly compact, stone-like consistency. Poses a significant problem the disposal here because these scattering materials only heavily or not at all weather or rot.

So wird nach der EP-PS 0 013 915 und 0 014 343, sowie der DE-PS 31 21 403 und 29 02 079 aus Quarzmehl und gebranntem Kalk unter Zugabe von Wasser ein dünnbreiiges Gemisch hergestellt, das mittels anionenaktiven grenzflächenaktiven Tensiden zu einer mikroporigen Masse aufbereitet wird, die in Gießformen eingefüllt wird und nach Erstarrung mittels einer Schneidvorrichtung in Steinformate geschnitten wird, die dann einer Autoklavenhärtung bei 10 bis 16 bar Dampfdruck unterzogen werden und schließlich das gehärtete Calciumsilikatgestein in Brecheranlagen zu feinkörnigem Granulat aufbereitet. Da dieses Calciumsilikat einen stark alkalischen pH-Wert aufweist, ist zur Erzielung einer effizienten Geruchsbindung eine Behandlung mit den pH-Wert senkenden Salzlösungen auf ein neutrales Niveau.So according to EP-PS 0 013 915 and 0 014 343, and the DE-PS 31 21 403 and 29 02 079 made of quartz flour and burned Lime with the addition of water is a thin paste mixture prepared by means of anionic surfactants Surfactants is processed into a microporous mass, which in  Casting molds are filled and after solidification using a Cutting device is cut into stone formats, which then autoclave curing at 10 to 16 bar steam pressure undergo and finally the hardened Calcium silicate rock in crushing plants to fine-grained Granules processed. Because this calcium silicate is a strong has an alkaline pH to achieve one efficient odor control treatment with the pH value lowering salt solutions to a neutral level.

Nach der WO 91/ wird eine hochporöses Granulat aus gebranntem Ton dadurch hergestellt, daß zunächst Ton und andere Substanzen wie Quarzsand und Feldspat mit Wasser unter Beimischung eines Verflüssigers aufbereitet und die Masse danach zu Formkörpern verarbeitet und schließlich gebrannt wird. Das gebrannte Produkt wird anschließend auf die gewünschte Fraktion gebrochen und mit einem den pH-Wert senkenden Säuresalz behandelt, so daß der pH-Wert nach der Behandlung zwischen pH-5 und pH-8 liegt.According to WO 91/, a highly porous granulate is made fired clay produced by first clay and other substances like quartz sand and feldspar with water underneath Admixed a condenser and processed the mass then processed into moldings and finally fired becomes. The burned product is then on the desired fraction broken and with a pH value lowering acid salt treated so that the pH after the Treatment is between pH-5 and pH-8.

Produkte dieser Art sind zwar in vorteilhafter Weise als Tierstreu geeignet, erfordern jedoch ein sehr aufwendiges Produktionsverfahren.Products of this type are admittedly advantageous as Suitable for animal litter, but require a very complex Production process.

Naturprodukte und synthetisch hergestellte Produkte weisen insbesondere zur Ad- und Absorption von Flüssigkeiten nur eine unzureichende Saugfähigkeit auf.Show natural products and synthetically manufactured products especially for the adsorption and absorption of liquids only one insufficient absorbency.

Insoweit besitzen Granulate auf Bentonitbasis vor allem für den genannten Verwendungszweck als Tierstreu wesentliche Vorteile. Bentonit-Produkte haben aufgrund ihrer extrem hohen Saugfähigkeit den weiteren Vorteil, daß sie in Kontakt mit Flüssigkeiten zur Agglomerierung neigen, so daß entsprechende feuchte Zonen sofort lokalisierbar sind. Zum Beispiel bei Verwendung als Tierstreu hat dies den Vorteil, daß nach einer gewissen Benutzungsdauer nicht die gesamte Tierstreu aus dem Konfektionierungsbehälter ausgetauscht werden muß; vielmehr können die benutzten Partien in Klumpenform gezielt entfernt und entsorgt werden.In this respect, granules based on bentonite are mainly used for the stated purpose as animal litter essential Benefits. Bentonite products have extremely high Absorbency has the further advantage that it is in contact with Liquids tend to agglomerate, so that corresponding damp zones can be localized immediately. For example Use as animal litter has the advantage that after a the entire animal litter from the  Assembly container must be replaced; much more can remove the used batches in a targeted manner and be disposed of.

Hierdurch werden der Verbrauch und damit die Entsorgungsmengen deutlich reduziert.As a result, the consumption and thus the disposal quantities significantly reduced.

Ein entscheidender Nachteil der Bentonit-Granulate ist jedoch ihr vergleichsweise hohes Schüttgewicht von circa 900 bis g/l.A crucial disadvantage of bentonite granules is, however their comparatively high bulk density of around 900 to g / l.

Demgegenüber liegen die Schüttgewichte von porosierten Granulaten aus Calciumsilikat oder gebranntem Ton um etwa 50% niedriger und zwar bei 400 bis 500 g/l.In contrast, the bulk weights of porous Granules made of calcium silicate or fired clay by about 50% lower at 400 to 500 g / l.

Der Erfindung liegt die Aufgabe zugrunde, ein Granulat der gattungsmäßigen Art anzubieten, welches ein möglichst geringes Schüttgewicht aufweist, eine hohe Ad- und Absorptionsfähigkeit gegenüber Flüssigkeiten aufweist, in einem wirtschaftlichen Verfahren preiswert und einfach herstellbar ist und im übrigen vorzugsweise auch eine visuelle Lokalisierung von mit Flüssigkeit in Berührung gekommenen Abschnitten ermöglicht.The invention has for its object a granulate to offer a generic type, which is as small as possible Has bulk density, a high adsorption and absorption capacity exhibits liquids in an economical Process is inexpensive and easy to manufacture, and the rest preferably also a visual localization of with Allows liquid to come into contact with sections.

Der Erfindung liegt die Erkenntnis zugrunde, daß dieses Ziel mit einem Granulat erreichbar ist, welches aus einem körnigen porösen Trägermaterial besteht, welches auf seiner Oberfläche eine selbsttragende Beschichtung aus einem hochquellfähigen (ungebrannten) Tonmineral aufweist. Der Begriff "Tonmineral" umfaßt dabei zunächst alle Arten von Tonen und/oder Tonmineralen, also ebenso 2-Schicht wie 3-Schicht-Minerale oder Kombinationen daraus.The invention is based on the knowledge that this goal can be reached with a granulate which consists of a granular porous carrier material, which is on its surface a self-supporting coating from a highly swellable (Unfired) clay mineral. The term "clay mineral" includes all types of clays and / or Clay minerals, i.e. 2-layer as well as 3-layer minerals or combinations thereof.

Ein solches Granulat läßt sich nicht einfach durch Mischung eines trockenen Tonmineral-Pulvers mit einem porösen Trägermaterial realisieren; vielmehr ist es notwendig, um ein staubfreies Produkt zu erhalten, die Tonmineralkomponente in einer adäquaten Flüssigkeitsmenge aufzuschlämmen und das poröse, feinkörnige Trägermaterial in dieser Tonmineralaufschlämmung homogen einzumischen, so daß die gewünschte Oberflächenbedeckung des porösen Trägermaterials mit dem quellfähigen Tonmineral optimal eingestellt werden kann. Die anschließende Trocknung bewirkt einen festen Verbund und ein quasi staubfreies Granulat.Such granules cannot simply be mixed a dry clay mineral powder with a porous Realize carrier material; rather, it is necessary to get one to get dust-free product, the clay mineral component in  slurrying an adequate amount of liquid and that porous, fine-grained carrier material in this Mix in clay mineral slurry homogeneously so that the Desired surface coverage of the porous carrier material can be optimally adjusted with the swellable clay mineral can. The subsequent drying creates a firm bond and a quasi dust-free granulate.

In ihrer allgemeinen Ausführungsform betrifft die Erfindung danach ein Produkt zur Ad- und/oder Absorption von Flüssigkeiten in Granulatform, wobei das ProduktIn its general embodiment, the invention relates then a product for the ad- and / or absorption of Liquids in granular form, the product

• - 25 bis 60 Gew.-Teile mindestens eines hochquellfähigen Tonminerals,

  - 25 to 60 parts by weight of at least one highly swellable Clay minerals,

• - 40 bis 75 Gew.-Teile eines körnigen, porösen Trägermaterials aufweist und die Tonmineralkomponente die Oberfläche des körnigen Trägermaterials im schlüssigen Verbund in quasi gleichmäßiger Schichtdicke bedeckt.

  - 40 to 75 parts by weight of a granular, porous carrier material and the clay mineral component has the surface of the granular carrier material in a coherent bond in quasi uniform layer thickness covered.

"Bedeckt" heißt, daß die vorzugsweise feinteilige Tonmineralkomponente auf der Oberfläche des Trägermaterials vorliegt. Die Bedeckung sollte hierbei so komplett wie möglich sein, um die Effekte der Erfindung bestmöglich ausnutzen zu können."Covered" means that the preferably finely divided Clay mineral component on the surface of the substrate is present. The coverage should be as complete as possible to take full advantage of the effects of the invention can.

Zu den hochquellfähigen Tonmineralen zählen vor allem die 3- Schicht-Tonminerale und hier Bentonit (einschließlich Montmorillonit).The highly swellable clay minerals include above all the 3- Layered clay minerals and here bentonite (including Montmorillonite).

Gegenüber reinen Bentonit-Produkten mit Schüttgewichten von ca. 900 bis ca. g/l besteht der Vorteil der erfindungsgemäßen Granulate insbesondere darin, daß Granulate mit Schüttgewichten von ca. 400 bis ca. 600 g/l herstellbar sind, wobei die bei Befeuchtung angestrebte Klumpenbildung vollwirksam erhalten bleibt und insgesamt infolge der höheren Porosität die Ab- bzw. Absorptionskapazität der Granulate quasi verdoppelt wird.Compared to pure bentonite products with bulk weights of approx. 900 to approx. g / l there is the advantage of Granules according to the invention in particular in that granules can be manufactured with bulk weights of approx. 400 to approx. 600 g / l are, the lump formation aimed at moistening remains fully effective and overall as a result of the higher  Porosity is the absorption or absorption capacity of the granules is almost doubled.

Ein bevorzugtes poröses Trägermaterial ist gemäß der Erfindung feinteiliges Calciumsilikat und/oder feinteiliges Porenbetonmaterial. Derartige poröse Trägermaterialien sind in erheblicher Menge als Entsorgungsprodukte aus der Baustoffproduktion verfügbar und werden erfindungsgemäß als Recyclate verwertet.A preferred porous support material is according to the invention finely divided calcium silicate and / or finely divided AAC material. Such porous support materials are in considerable amount as disposal products from the Building material production available and are invented as Recycled recycled.

Die mittlere Korngröße der herzustellenden Granulate ist variabel darstellbar und wird von der Korngröße des porösen Trägermaterials bestimmt. Für den erfindungsgemäßen Verwendungszweck rollte die Korngröße der Granulate zwischen 0,5 und 4,0 mm, vorzugsweise zwischen 0,5 und 2 mm ausgerichtet sein. Befeuchtete Partien bewirken lokalisierte Klumpenbildung (Agglomeration), wobei die Eindringtiefe im Materialbett von der Korngröße der Granulate beeinflußt wird. Die benutzten Stellen sind visuell jederzeit erkennbar und können als kompakte Klumpen aus dem Einstreubett entnommen werden.The average grain size of the granules to be produced is variably representable and is based on the grain size of the porous Carrier material determined. For the invention The grain size of the granules was used between 0.5 and 4.0 mm, preferably between 0.5 and 2 mm be aligned. Moistened areas cause localized Lump formation (agglomeration), the depth of penetration in the Material bed is influenced by the grain size of the granules. The places used are visually recognizable at all times can be taken as compact clumps from the bedding will.

Die Tonmineralkomponente sollte in möglichst feinteiliger Form als Mehl vorliegen, wodurch die Quellfähigkeit begünstigt wird.The clay mineral component should be in the finest possible form available as flour, which promotes swellability becomes.

Das poröse Trägermaterial "Calciumsilikat/Porenbeton" ist je nach Herstellungsverfahren in unterschiedlichen Schüttgewichten und Korngrößen verfügbar. Im Sinne der Erfindung sind Schüttgewichte von ca. 300 bis ca. 400 g/l bevorzugt. The porous carrier material "calcium silicate / cellular concrete" is ever according to manufacturing processes in different Bulk weights and grain sizes available. In the sense of the Invention are bulk weights of approximately 300 to approximately 400 g / l prefers.  

Auf der Zeichnung ist ein Sekundärgranulat stark vergrößert dargestellt.A secondary granulate is greatly enlarged in the drawing shown.

Dieses Sekundärgranulat besteht aus dem Trägermaterial in Form eines porösen Grundkornes (1) und einem Mantel (2) aus einer Bentonitschicht, die das Grundkorn (1) vollflächig umgibt und mit der Oberfläche des Grundkornes (1) sowie dessen Poren (3) herstellungsmäßig verbunden ist. Die Schichtstärke des Mantels (2) liegt z. B. zwischen ca. 0,25 mm und 0,5 mm.This secondary granulate consists of the carrier material in the form of a porous basic grain ( 1 ) and a jacket ( 2 ) made of a bentonite layer, which completely surrounds the basic grain ( 1 ) and is connected to the surface of the basic grain ( 1 ) and its pores ( 3 ) in terms of production . The layer thickness of the jacket ( 2 ) is z. B. between about 0.25 mm and 0.5 mm.

Das Sekundärgranulat ist auf der Zeichnung auf der linken Hälfte als von dem Mantel (2) umgebene Vollkorn und auf der rechten Hälfte im Schnitt dargestellt.The secondary granulate is shown in the drawing on the left half as whole grain surrounded by the casing ( 2 ) and on the right half in section.

Die Herstellung der Körnungen zur Verwendung als Hygiene- Tierstreu ist denkbar einfach.The production of the grits for use as a hygiene Animal litter is very easy.

Beispiel 1

example 1

In eine Misch-Granuliervorrichtung werden 150 kg Wasser eingefüllt und mit 125 kg Bentonitmehl zu einer dünnbreiigen Schlämme aufbereitet. In diese Bentonitschlämme werden 375 kg Primärkörnung (1) in der Korngröße kleiner als 1,5 mm in Form von mikroporigem Calciumsilikat und/oder Porenbeton eingemischt. Die Primärkörnung (1) wird im Mischvorgang mit einer gleichmäßigen Schichtdichte der Bentonitschlämmung (2) umhüllt, wobei Granulate in der Korngröße bis ca. 2,0 mm gebildet werden. Dieses quasi erdfeuchte Sekundärgranulat wird im Heißluftstrom getrocknet, und mittels Siebmaschine von vorhandenem Unterkorn und Überkorn in der gewünschten Granulatgröße selektiert. Schüttgewicht nach Trocknung ca. 450 g/l. 150 kg of water are poured into a mixing / granulating device and processed with 125 kg of bentonite flour to form a thin-slurry slurry. 375 kg of primary grain ( 1 ) with a grain size of less than 1.5 mm in the form of microporous calcium silicate and / or aerated concrete are mixed into these bentonite slurries. In the mixing process, the primary grain ( 1 ) is coated with a uniform layer density of the bentonite slurry ( 2 ), granules with a grain size of up to approximately 2.0 mm being formed. This quasi earth-moist secondary granulate is dried in a hot air stream and selected from the undersize and oversize in the desired granule size using a sieving machine. Bulk weight after drying approx. 450 g / l.

Beispiel 2

Example 2

Nach der in Beispiel 1 benannten Verfahrensweise werden 200 kg Wasser mit 250 kg Bentonitmehl zu einer Bentonitschlämme aufbereitet und mit 250 kg Primärkörnung der in Beispiel 1 benannten Art und Korngröße zu Sekundärgranulat aufbereitet. Schüttgewicht nach Trocknung = ca. 525 g/l.According to the procedure described in Example 1, 200 kg Water with 250 kg of bentonite flour to form a bentonite slurry processed and with 250 kg primary grain of that in Example 1 named type and grain size processed into secondary granules. Bulk weight after drying = approx. 525 g / l.

Beispiel 3

Example 3

Verfahrensweise analog zu Beispiel 1 und/oder 2, jedoch mit Primärkorn (1) in der Korngröße kleiner als 3,0 mm. Korngröße des Sekundärgranulates ca. 4,0 mm. Schüttgewicht nach Trocknung ca. 400 g/l bis 450 g/l.Procedure analogous to example 1 and / or 2, but with primary grain ( 1 ) in the grain size smaller than 3.0 mm. Grain size of the secondary granules approx. 4.0 mm. Bulk weight after drying approx. 400 g / l to 450 g / l.

Beispiel 4

Example 4

Das mit einer Restfeuchte von ca. 25 Gewichtsprozent aus mikroporigem Calciumsilikat und/oder Porenbeton anstehende Grundkorn (1) wird zusätzlich mittels Wasserbesprühung auf einen Feuchtegrad von ca. 35 Gewichtsprozent angefeuchtet und in einer Mischvorrichtung mit trockenem Bentonitmehl aufgepudert, wobei die auf das Grundkorn (1) aufgebrachte Oberflächenfeuchte die gebildete Bentonitaußenschale (2) durchdringt und eine gleichmäßige Umhüllung des Grundkorns (1) in der gewollten Schichtdicke auf Bentonit (2) sicherstellt, die sich bei der nachfolgenden Trocknung verfestigt.The pending with a residual moisture content of about 25 percent by weight of micro-pore calcium silicate and / or aerated granular core (1) is additionally moistened by means of water spray to a moisture level of about 35 weight percent and dusted in a blender with dry Bentonitmehl, wherein the on the base particle (1 ) applied surface moisture which Bentonitaußenschale formed (2) penetrates, and a uniform coating of the base grain (1), ensures that solidifies upon subsequent drying in the intended layer thickness on bentonite (2).

Entscheidend bei der erfindungsgemäßen Verfahrensweise ist, daß im Trocknungsvorgang eine hohe Eigenstabilität der Tonmineralbeschichtung des porösen Trägermaterials erreicht wird. Es wird ein quasi staubfreies Granulat erhalten, das den angestrebten Hygieneanspruch optimal erfüllt, wobei der Bentonitanteil im Vergleich zum Stand der Technik bis zu 75 Gewichtprozent reduziert wird und gleichzeitig die Granulatbedarfsmenge wegen der überlegenen Saugkapazität wesentlich verringert werden kann.What is decisive in the procedure according to the invention is that in the drying process a high inherent stability of the Clay mineral coating of the porous carrier material reached becomes. A quasi dust-free granulate is obtained which desired hygiene requirements optimally met, the Bentonite content up to 75 compared to the prior art Weight percent is reduced and at the same time the  Quantity of granules required due to the superior suction capacity can be significantly reduced.

Ein weiterer Vorteil besteht darin, daß dieses Tierstreugranulat leicht und problemfrei entsorgbar ist, da dieses durch Witterungseinflüsse in seine Bestandteile zerfällt und zur Bodenauflockerung beiträgt.Another advantage is that this Animal litter granules can be easily and easily disposed of because this due to weather influences in its components disintegrates and contributes to soil loosening.

Bei einem weiteren Verfahren zur Herstellung von hochporösem Granulat zur Verwendung als Tierstreu wird das poröse, saugfähige Grundkorn (1) aus Calciumsilikat mit einer wässerigen Lösung angefeuchtet, in welcher 0,5 bis 2,5 Gewichtsprozent, vorzugsweise 1,5 Gewichtsprozent, einer kaltquellenden Stärke, vorzugsweise eine Maisstärke, gelöst sind, und danach erfolgt die Ummantelung (2) mit einem hochquellfähigen in Mehlfeinheit vorliegenden Tonmineral­ vorzugsweise Bentonit, wobei der auf der Oberfläche des porösen, saugfähigen Grundkorn gebildete klebrige Film in die aus hochquellfähigem Tonmineralmehl aufgebaute Deckschicht eindringt, und nach Trocknung einen schlüssigen, rissfreien, festen Haftverbund bildet.In a further process for producing highly porous granules for use as animal litter, the porous, absorbent basic grain ( 1 ) made of calcium silicate is moistened with an aqueous solution in which 0.5 to 2.5 percent by weight, preferably 1.5 percent by weight, of a cold-swelling starch , preferably a corn starch, and then the coating ( 2 ) is carried out with a highly swellable clay mineral, preferably bentonite, in flour fineness, the sticky film formed on the surface of the porous, absorbent base grain penetrating into the top layer composed of highly swellable clay mineral flour, and after Drying forms a coherent, crack-free, firm adhesive bond.

Durch den Zusatz der Maisstärke wird eine äußerst sichere und dauerhafte Verbindung (praktisch Verklebung) von Ummantelung (2) und Grundkorn (1) erreicht, und ein diese optimale Verbindung erzielendes Verfahren gelöst.By adding the corn starch, an extremely secure and permanent connection (practical gluing) of the casing ( 2 ) and base grain ( 1 ) is achieved, and a process that achieves this optimal connection is achieved.

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