Drying bentonite

Soda. Ash Roasting. Some of the first processes to recover selenium on a commercial basis were based on roasting of copper slimes with soda ash to convert both selenium and tellurium to the +6 oxidation state. Eigure 1 shows flow sheets for two such processes. Slimes are intensively mixed with sodium carbonate, a binder such as bentonite, and water to form a stiff paste. The paste is extmded or peUetized and allowed to dry. Care in the preparation of the extmdates or pellets is required to ensure that they have sufficient porosity to allow adequate access to the air required for oxidation. 

Suspension Polymerization. This method (10) might be considered as a number of bulk polymerizations carried out simultaneously in the monomer droplets with water acting as a heat-transfer medium. A monomer-soluble initiator, eg, a peroxide or azo compound, and a protective coUoid like poly(vinyl alcohol) or bentonite, are requited. After completion of the polymerization, the excess of monomer(s) is steam stripped, and the beads of polymer are collected and washed on a centrifiige or filter and dried on a vibrating screen or by means of an expeUer—extmder. 

Type of dryer tions, extracts, milk, blood, waste liquors, rubber latex, etc. gents, calcium carbonate, bentonite, clay sbp, lead concentrates, etc. trifuged sobds, starch, etc. dry. Examples centrifuged precipitates, pigments, clay, cement. ores, potato strips, synthetic rubber. objects, rayon skeins, lumber. sheets. her sheets. 

Clay (see bentonite. Biller s earth, kaolin, and Salt cake, dry, coarse 85 D27... 

Microwave chemistry has been found to be a useful method for accelerating reactions or catalyzing reactions that are difficult to carry out by other methods. A modification of the Hantzsch method to directly obtain pyridines has been communicated. A dry medium using ammonium nitrate bentonitic clay system with microwave irradiation affords pyridines 96 in a single pot within 5 minutes. When the pyridine is not the major product (> 75% yield), the dealkylated pyridine 97 becomes an... 

Since 1960, the inner core has been made from c/5-poly-butadiene by the compression moulding technique. This replaced the earlier material made from a suspension of barytes or bentonite clay in water and glycerine or the winding of rubber threads made from t /5-polyisoprene, either from latex or a dry rubber compound. A typical thread recipe is given Table 4. 

A specific weight of 12.8 Ib/gal is required for a Class A cement slurry. It is decided that the cement be mixed with bentonite to reduce the specific weight of the slurry. Determine the weight of bentonite that should be dry blended with each sack of cement. Determine the yield of the cement slurry. Determine the volume (gal) of water needed for each sack of cement. 

Bentonite is dry blended to the cement. The addition of bentonite requires more water. Bentonite has been used up to 25% by weight. The additive also increases the viscosity of the slurry. High amounts of bentonite increase the permeability and reduce the final strength, however. Therefore high concentrations of bentonite are not recommended. 

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)]. 

On-site sandy soils can also be blended with other clay soils available in the area, but natural clay soil is likely to form chunks that are difficult to break down into small pieces. Bentonites, obtained in dry, powdered forms, are much easier to blend with on-site sandy soils than are wet, sticky clods of clay. Materials other than bentonite can be used, such as atapulgite, a clay mineral that is insensitive to attack by waste. Soils can also be amended with lime, cement, or other additives. 

A colloidal clay used as a thickener in latex compounding and as a filler in dry rubber compounding the reaction of bentonite with amines has produced several useful rubber reinforcing fillers. 

The aluminium content of the two samples is comparable, when referred to the silica content of the original clay, and the two PILC have comparable surface areas after calcination at 300°C. The ACH bentonite was formed into small extrudates and flash-dried, whereas sample G5 was dried in a thin cake. In both cases, crushing to a fine powder was easy. Sample G5 retains a higher surface area at 800°C in spite of a higher potassium content. Therefore the K O content of the PILC is not the predominant factor for the thermal stability. 

The aged pillaring reagents were heated to 65 C and 325 bentonite, American Colloid Company, whose major constituent is the layered clay mineral, montmorilIonite, was added. There was always a 5-fold excess of aluminum in solution and the volume of solution per gram of clay was always 45 cc/g or more. The reaction was carried out for 2 hours. The slurry was filtered and the solids washed two times with water, dried, sized, and calcined at 500 C for 2 hours in air. 

The other iron-containing clay catalyst prepared by reacting a Texas bentonite with an ACH-Fe(N02)3 solution gave an (Fe.ACH)-bentonite sample containing 9.7% Fe2 3 after drying in air at 120 C/10h had d(OOl) = 17.8A and BET surface area of 296 m /g. Calcination reduced pillar s height after heating in air at 400 C/10h, the d(OOl) value decreased to about 15.7A probably as a result of some iron removal from the pillars. 

Fig. 1. Hydroxyl absorption bands for several smectites pillared with aluminum chlorhydroxide (ACH) soluctions A) Wyoming ACH-bentonite B) Texas ACH-bentonite C) Fe-bentonite D) ACH- Fe bentonite) E) (ACH, Fe)-bentonite and F) ACH-nontronite. Samples a) have been dried at 200 C and then loaded with pyridine and degassed at b) 200 C, c) 300 C, d) 400 C and e) 500 C in vacuo for 2 hours at each temperature.

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