Calcium bentonite

Clays used in foundries include hydrous alumina silicates, known as bentonites. Their properties provide cohesion and plasticity in the green state and also high strength when dried. There are three clays that are commonly used in foundries western bentonite [sodium bentonite, burnout point 1290°C (2350°F)], southern bentonite [calcium bentonite, burnout point 1065°C (1950°F)], and fire clay [kaolinite, burnout point 1425°C (2600°F)]. 

Calcium bentonite, as though more permeable than sodium bentonite, has also been used for soil blends. Approximately twice as much calcium bentonite typically is needed however, to achieve a hydraulic conductivity comparable with that of sodium bentonite. One problem with using sodium bentonite, however, is its vulnerability to attack by chemicals and waste leachates, a problem that will be discussed later. 

Since calcium bentonite, typically, is 100-1000 times more permeable than sodium bentonite, the introduction of this permeating liquid could change hydraulic conductivity substantially. 

Calcium bentonites, 6 664—666, 696 Calcium borosilicate, allowed pigment in... 

Calcium. Excess calcium can occur in wines stored in concrete tanks or otherwise exposed to calcium (filter aids, calcium bentonite, etc.). After fortified wines are bottled, calcium tartrate may slowly precipitate. 

Wear nitrile rubber gloves, laboratory coat, and self-contained breathing apparatus. Cover the spill with a 1 1 1 mixture by weight of sodium carbonate, clay cat litter (calcium bentonite), and sand. When all of the liquid has been absorbed, scoop the mixture into a plastic pail or other wide-mouth container and place in the fume hood. If local regulations permit, allow the acetone vapor to evaporate for several days until no odor remains. The spill mix can then be discarded with normal refuse.14,15 Otherwise, package and label for disposal by burning.15,16... 

Nagy, N. M., and J. Konya. 1988. The interfacial processes between calcium-bentonite and zinc ion. Coll. Surf. 32 223-235. 

In our studies, the model substance (montmorillonite) was a calcium bentonite (Istenmezeje, Hungary), the characteristic features of which are given here. X-ray diffraction (intensity of the basal reflection) and thermoanalytical (weight loss upon heating) data show 91% montmorillonite content. The other constituents are 5% calcite, 3% kaolinite, 1% x-ray amorphous silicates, and a trace of quartz. The amorphous phase is silicate particles, which are not crystalline for... 

The most important industrial example of cation exchange is the preparation of sodium-montmorillonite/bentonite from calcium bentonite. As seen in Table 2.2, calcium ions have greater affinity to the layer charge than sodium ions, so the calcium-sodium cation exchange must be performed in the presence of carbonate ions. It means that calcium-montmorillonite/bentonite is suspended in sodium carbonate solution. Calcium ions precipitate with carbonate ions, so sodium ions can occupy the interlayer space. This process is known as soda activation of bentonite. The disadvantage of soda activation is that sodium-montmorillonite is contaminated with calcium carbonate. 

The parameters obtained by others for SWy-2, BSAB, and MX-80 cannot be compared to the previously discussed data because the silanol and aluminol sites as well as the deprotonation processes (Equations 2.4 and 2.5) were treated together. Calcium bentonite (Istenmezeje) shows similar intrinsic stability constant for SWy-1 bentonite, but the number of edge sites is different. Note, however, that the specific external surface areas are also very different 21.4 m2/g for SWy-1, and 93.5 m2/g for Istenmezeje montmorillonite (Table 2.1). The ratio of the specific surface area (Istenmezeje/SWy-1) is 4.4, and the ratio of the total number of edge sites (silanol + aluminol) is 5.3, which are in fairly good agreement if the surface charge density is the same. 

Konya, J., N. M. Nagy, and K. Szabo. 1988. The study of the ion exchange processes in system of zinc ions and calcium-bentonite, clay soil, humate and sand by radioisotopic labelling method. React. Polym. 7 203-209. 

The surface acid-base parameters of bentonites from Sajobabony can be compared to similar parameters of other bentonites samples (Chapter 2, Section 2.4.3, Table 2.4). As mentioned in Chapter 2, Section 2.4.3, the parameters of SWy-2, BSAB, and MX-80 from the literature, cannot be compared to the data of bentonite samples from Sajobabony because the deprotonation of silanol and aluminol sites are treated together. Calcium bentonite (Istenmezeje, HU) shows similar characteristics as sedimentary bentonites, while the ratio of the amount of the edge site and the deprotonation intrinsic stability constant of SWy-1 bentonite is similar to the data of the bentonitic tuff. 

French town (Montmorillon) where it was first discovered. In the USA, bentonite is principally mined in Wyoming - hence the term Wyoming clay . The type of bentonite, the source, and its purity influence its properties (Marchal et al. 1995). Bentonite is a complex hydrated aluminum silicate with exchangeable cationic components (Al, Fe, Mg) Si40io (0H)2 (Na+, Ca++). The most commonly used bentonite form in enology is the sodium bentonite. Sodium bentonite has enhanced protein binding capabilities over calcium bentonite. 

One other material has actually been used on commercial projects. This is Montan Wax, used in Europe. It is a hard, high melting point, non-hazardous material, extracted from coal and peat deposits. Montan wax grout is a suspension-type grout, consisting of a stable emulsion of Montan wax (20%), water (78%), and an emulsifier (2%). To break the emulsion, 2-5% sodium or calcium bentonite clay is added just prior to injection. The mixture is very viscous, due to the addition of bentonite, and set time is difficult to control, ranging from half an hour to several hours. Elowever, the material is nontoxic, and low in cost. 

Table 1.11). Independently of any accidental contamination, calcium added in the form of calcium bentonite for treating must or wine. 

Acid and calcium bentonites are easy to disperse without forming lumps. Suspensions settle rapidly, leaving the liquid turbid but with a relatively light deposit. Protein adsorption is limited. 

Sodium bentonite is most frequently used to treat wines. The flakes are more widely spaced (100 A) than those of calcium bentonite (10 A), so they swell more in wine and have a higher protein adsorption capacity. Sodium bentonite flakes are relatively difficult to mix into suspension in water, but the suspensions have a very stable colloidal character. When added to wine, they produce flocculation and settle out as a flaky deposit, leaving a clear liquid. The natural proteins are completely eliminated and the wine is protected from protein (Section 5.6.2) and copper casse (Section 4.7.3). 

The swelling number represents the ratio between the volume of 5 g of bentonite powder and the volume occupied by 5 g of bentonite left in 100 ml water for 24 hours. Various forms of bentonite behave differently (Table 10.7) and swelling is also affected by the type of water, especially in the case of sodium bentonite (Maujean, 1993). The and Mg + cations in tap water take the place of the smaller Na" and K+ cations in the bentonites, thus increasing the swelling number. This phenomenon is not observed in calcium bentonite, where, on the contrary, the swelling volume decreases. 

The quantity of proteins adsorbed (egg or BSA blood albumin) may also be measured. Sodium bentonite has a higher adsorption capacity (Table 10.7) than calcium bentonite, which explains why it is preferred for treating wine. 

Natural calcium bentonites do not swell or gel when mixed with water. They are rarely used at present, being used only for very special castings. Alternatively, these materials may be "activated" by treatment with soda ash to give "soda activated bentonites". These are used extensively in ferrous foundries throughout Europe their properties proach those of natural sodium bentonites. 

A further group of nanocomposites are the well-known bentonites, revitalized at the end of the 1980s by Toyota Research. Bentonites are swellable, three-layer silicates consisting mainly of montmorillonite. The new organophilic bentonite Nanofil product family from Siid Chemie AG is based partly on the Bavarian calcium bentonites, which are activated by acid leaching [see Table 27 [77]], and do without cationic exchange. (Author s remark With a mean particle size of 4 pm, these are by no means nanoparticles ). 

Table 27 Nanofil fillers based on unmodified, acid-activated calcium bentonite (Slid Chemie AG)...

Spilled liquids often may be diluted with water and simply mopped up or, in some cases, eliminated by spreading an absorbent material, such as vermiculite or a clay absorbent (such as calcium bentonite) on the spilled material or, a bit more neatly, but much more expensively, by placing pillows or pads containing an absorbent material on the liquid, after which the absorbent material is collected into containers for later disposal. 

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