Phosphate tricalcium

Several compounds of the CaO—P2O3—H2O system are given in Table 8. The common names for the mono-, di-, and tricalcium phosphates arise from the traditional double-oxide formulas, CaO 2i5p T2O3, 2CaO H2O +205, and 3CaO +205, respectively. These terms are routinely used in industry. With the exception of the monocalcium salt, the calcium phosphates are all sparingly soluble. 

Tricalcium phosphate, Ca2(P0 2> is formed under high temperatures and is unstable toward reaction with moisture below 100°C. The high temperature mineral whidockite [64418-26-4] although often described as P-tricalcium phosphate, is not pure. Whidockite contains small amounts of iron and magnesium. Commercial tricalcium phosphate prepared by the reaction of phosphoric acid and a hydrated lime slurry consists of amorphous or poody crystalline basic calcium phosphates close to the hydroxyapatite composition and has a Ca/P ratio of approximately 3 2. Because this mole ratio can vary widely (1.3—2.0), free lime, calcium hydroxide, and dicalcium phosphate may be present in variable proportion. The highly insoluble basic calcium phosphates precipitate as fine particles, mosdy less than a few micrometers in diameter. The surface area of precipitated hydroxyapatite is approximately... 

Tricalcium Phosphate. Commercial tricalcium phosphate (TCP) is actually an amorphous basic calcium phosphate close to hydroxyapatite in composition. Because of its extremely low solubiUty in water, TCP is precipitated almost quantitatively from dilute phosphate solutions with a slurry of hydrated lime. TCP is separated by dmm-, spray-, or flash-drying the TCP slurry, with or without intermediate sedimentation or filtration steps. It is used as an industrial-grade flow conditioner and parting agent. 

For free-flow agents, water-insoluble, finely divided adsorbents such as sodium siUcoalurninate, tricalcium phosphate, calcium siUcate, magnesium carbonate, and siUcon dioxide are used. Concentrations between 0.5 and 2% are typically added to table salt and some industrial grades of salt for use in apphcations where caking may occur. 

Other Ceramic Calcium Phosphate Materials. Other ceramic calcium phosphate materials for repairing bony defect iaclude p-tricalcium phosphate (P-TCP) [7758-87-4], P-Ca2(PO, and biphasic calcium phosphate (BCP) ceramics which consist of both P-TCP and HA. Unlike ceramic HA, P-TCP resorbs ia the tissue (293). The in vivo dissolution of BCP ceramic implants was shown (296) to iacrease with increasing P-TCP/HA ratio ia the implants. Both P-TCP and BCP can lead to new bone growth to various extents depending on the appHcations and the type of materials used (293,296). 

The kinetic equation can vary with a number of factors. For the reaction between tricalcium phosphate and urea, relatively coarse material (-180-1-200 mesh) obeyed the law x = kt with E = 18 kcaP g mol (32,400 Btu/lb mol) and finer material (—300f320 mesh) obeyed a first-order equation with E = 28 kcaPg mol. 

By far the largest source of phosphorus is phosphate rock, with some use of phosphatic iron ore, from which phosphorus is obtained as a by-product from the slag. Phosphate rock consists of the insoluble tricalcium phosphate and other materials. For use as a fertilizer, phosphate must be converted to the water soluble form, phosphoric acid (H3PO4) which has three hydrogen atoms, all of which are replaceable by a metal. Tricalcium phosphate, is converted to soluble monocalcium phosphate and to superphosphate, A fertilizer factory, typically, a large installation, characterized by large silos produces year round, but peaks with the demands of the growing season. Phosphorus has many uses other than for fertilizer. 

The precipitation of anhydrite (anhydrous calcium sulfate, CaS04) may also occur. Under ambient temperatures, anhydrite is much more soluble than calcium carbonate, but because calcium sulfate, in common with other calcium salts such as calcium phosphate (also known as tricalcium phosphate [Ca3(P04)2]), has an inverse-temperature solubility, it deposits more rapidly on the hottest heat transfer surfaces. 

In particular, where polyphosphate is added either to the MU waterline (say, as a stabilizer against the risks of after-precipitation) or to the FW line or FW tank (as a precipitating treatment for residual hardness), there is some risk of FW line phosphate deposits developing. Such deposits are likely to be primarily composed of hard, intractable calcium phosphate [tricalcium phosphate Ca3(P04)2] scale, but they may include magnesium phosphate [Mg3(P04)2] and other insoluble phosphates and hydroxides. The risk of precipitation and subsequent deposition is increased where the pH is below 8.3, if the FW line is particularly long, or when the FW temperature is high. 

Phosphate is sometimes present in MU water sources (say, 1-2 ppm or more) usually as a result of field and factory run-off or from the deliberate addition as a city water threshold agent to prevent corrosion and deposition in the mains. The steady growth in the reuse of secondary water sources such as municipal and industrial waste waters means that phosphate is increasingly likely to be present in MU. If the phosphate remains undetected, it likely will scale and foul FW lines by forming amorphous calcium orthophosphate [tricalcium phosphate Caj(P04)2] sludge before it reaches the boiler section. 

NOTE Depending on operating conditions, alkalinity, pH level, point of feed, and so forth, when phosphate is present in the BW, calcium salts precipitate primarily as either insoluble tricalcium phosphate [Ca3(P04)2] or hydroxyapatite [Ca]0(0H)2(P04)6J. 

Some phosphate-cycle reactions are shown below, and, although for the sake of simplicity only calcium phosphate is shown as a precipitant, depending on the operational circumstances, the reaction produces either tricalcium phosphate, hydroxyapatite, or a combination of both salts. 

The formula for tricalcium phosphate is Ca3(P04)2 and that of hydroxyapatite (which is a complex, composed of a mixed phosphate and hydroxide) is variously written as ... 

Hydroxyapatite produces a soft sludge that is not as sticky as tricalcium phosphate and can be more easily managed (dispersed) by a (polymeric) sludge conditioner. 

NOTE Higher incoming hardness ultimately results in a reduction in BW alkalinity because the various hardness and phosphate reactions consume alkalinity in the production of tricalcium phosphate and hydroxyapatite. 

Phosphate-based sludges and deposits such as hydroxyapatite [Ca10(OH)2(PO4)6] and tricalcium phosphate [Ca3(P04)2] usually dissolve to some degree when tested with concentrated HC1, but there is no fizz . 

Kutty and Murthy [1159] have made a kinetic study of the solid—solid reaction between tricalcium phosphate and urea nitrate, a process of possible technological importance. A reduction in particle size, notably of Ca3(P04)2, increased the rate of reaction in powder mixtures and also changed the kinetic characteristics (318—338 K). Reaction in relatively coarse material (between —180 and +200 mesh) obeyed the parabolic... 

In salt substitutes, the metallic or bitter taste of potassium chloride is often masked by other ingredients, such as the amino acid L-lysine, tricalcium phosphate, citric acid, and glutamic acid. 

Biomedical materials include ceramics such as the biologically active hydroxylapatite and tricalcium phosphate, and high-strength metals such as titanium alloys.These materials are not produced by CVD as this time, except on an experimental basis. CVD, however, is the major process used in the production of another very important biomedical material, i.e., isotropic... 

Brook, I. M., Craig, G. T. Lamb, D. J. (1991a). In vitro interaction between primary bone organ cultures, glass-ionomer cements and hydroxyapatite/tricalcium phosphate ceramics. Biomaterials, 12, 179-86. 

Hydroxy apatite (tricalcium phosphate) (tech grade) Dodecylbenzene sulfonate (tech grade)... 

Water 0.12 Polybutadiene 0.005 Tricalcium Phosphate 0.00006 f Dodecylbenzene Sulfonate 0.0025 Benzoyl Peroxide 0.004 Misc. 

Before the polystyrene is separated from the water and impurities, the insoluble inorganics must be dissolved. This is done by adding enough dilute hydrochloric acid to react with the tricalcium phosphate and make a soluble product. The acid will also react with any remaining peroxide. However, nearly all the peroxide will have already reacted or decomposed, since its half-life is 2.1 hr at 85°C.27... 

The additive feed tank must be large enough to handle all additives plus a carrier solution of styrene. The pounds of dodecylbenzene sulfonate, tricalcium phosphate, and benzoyl peroxide (50% water) used per batch are... 

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