Phosphates precipitation

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... 

If deposits are minimized, the areas where caustic can be concentrated is reduced. To minimize the iron deposition in 6.895-12.07 x 10 Pa boilers, specific polymers have been designed to disperse the iron and keep it in the bulk water. As with phosphate precipitation and chelant control programs, the use of these polymers with coordinated phosphate—pH treatment improves deposit control. 

Temperature of the system When inhibitors are used in the 0-100°C range it is usually found that higher concentrations become necessary at the higher temperatures Other inhibitors can lose their effectiveness altogether as the temperature is raised. A prime example of this is the polyphosphate type of inhibitor. This is effective in circulating systems at temperatures below about 40°C, but at higher temperatures reversion to orthophosphate can occur and this species is ineffective at the concentrations at which it will then be present. If calcium ions are present, additional loss of inhibitor will occur due to calcium phosphate precipitation. 

Innocuous sludges such as those resulting from using phosphate precipitation programs may cause severe fouling problems, especially when oil, saponifiable fats, or other deposit binders are present in the boiler. 

Phosphate precipitant treatments should almost always be added directly to the boiler shell or drum, or to the FW line as close as possible to the boiler. (The phosphate dosing pump should be interlocked with the FW pump when dosing to the FW line.)... 

When sulfates, carbonates, and other dissolved BW salts exceed their individual maximum solubility limits, they form sludges, scales, and deposits. This situation may arise either from a general overconcentration of the BW TDS (high COC) or from the deliberate precipitation of salts of selective ions, as occurs when using phosphate precipitation programs. 

Chelant programs These programs are commonly prescribed for both FT and WT boilers and are employed either as replacements for or used in combination with phosphate precipitation programs. 

Hardness precipitation and deposit control, functioning at a stoichiometric level. Phosphate precipitation programs utilize this function. 

NOTE This formula is appropriate for applications requiring enhanced dispersancy of phosphate precipitates and sludges. Use at 300 ppm in the boiler. This produces 12 ppm of active SSMA for phosphate dispersancy. 

NOTE This uses a chelant cleaner for phosphate-based programs. Although the feed rate is theoretically based on meeting the chelant demand, in practice, however, much of the demand is satisfied by the existing phosphate precipitant. The bulk of the EDTA is available to strip off old calcium deposits. Cycles of concentration should be limited. Use this formulation at 300 to 400 ppm in the boiler. At 400 ppm product, 30 ppm chelant is provided. 

Determining calcium levels normally does not identify hardness breakthrough because the calcium salt simply reacts with phosphate precipitant (or similar treatment) and is lost as a sludge. It does, however, produce an immediate and noticeable reduction in alkalinity. (Calcium bicarbonate breaks down to calcium carbonate and carbonic acid.)... 

Phosphate-polymer programs Phosphate precipitant, requirement to remove 419 430... 

Saturday, December 19, 1942. Today Thompson tested the use of bismuth phosphate as a carrier for 94 in its reduced state with rather encouraging results. Upon precipitating relatively high concentrations of bismuth (15-25 mg per 10 cc) as bismuth phosphate from 20% UNH solution, he finds the 94 to be carried to the extent of more than 85%. The bismuth phosphate precipitates are slow in forming and require digestion at temperatures of the order of 75°C. 

He finds that the bismuth phosphate precipitate is very dense and crystalline, which are desirable properties, and dissolves readily in HC1. 

Sodium carboxymethyl chitin and phosphoryl chitin had most evident influences on the crystallization of calcium phosphate from supersaturated solutions. They potently inhibited the growth of hydroxyapatite and retarded the rate of spontaneous calcium phosphate precipitation. These chitin derivatives were incorporated into the precipitate and influenced both the phase and morphology of the calcium phosphate formed (flaky precipitate resembling octacalcium phosphate instead of spherical clusters in the absence of polysaccharide) [175]. 

We thank the editors for including our manuscript even though we were unable to attend the conference. We thank M. Spicuzza for maintaining the laser extraction lines, J. O Neil, H. Frieke, and R. Blake for help with the silver phosphate precipitation and analysis, J. Farquhar,T. Chacko, andY. Kolodny forpro-viding standards, and J. Banfield, K. Barovich, L. Bamngartner, S. Baumgartner,... 

By investigating the effects of pH, it was shown that H2P04 was the actual precursor of lanthanum phosphate precipitation. The particle yield was proportional to the H2P04 concentratian. The number density was proportional to the square of the H2p04 concentration. A maximum particle size was obtained at an optimum precursor concentiation as a result of the tradeoff of the nuclealion and growth. 

C18-0127. Phosphate ions are a major pollutant of water supplies. They can be removed by precipitation using solutions of Ca ions because the of calcium phosphate is 2.0 X 10 . Suppose that 3.00 X 10 L of wastewater containing P 03 at 2.2 X 10 M is treated by adding 120 moles of solid CaCl2 (which dissolves completely), (a) What is the concentration of phosphate ions after treatment (b) What mass of calcium phosphate precipitates ... 

Classical gene transfer methods still in use today are diethylamino ethyl (DEAE)-dextran and calcium phosphate precipitation, electroporation, and microinjection. Introduced in 1965, DEAE-dextran transfection is one of the oldest gene transfer techniques [2]. It is based on the interaction of positive charges on the DEAE-dextran molecule with the negatively charged backbone of nucleic acids. The DNA-DEAE-dextran complexes appear to adsorb onto cell surfaces and be taken up by endocytosis. 

The correlation of phosphate precipitation with decrease of conductivity (Wilson Kent, 1968), increase in pH (Kent Wilson, 1969) and hardness (Wilson et al, 1972) is shown in Figure 6.16. These results demonstrate the relationship between the development of physical properties and the underlying chemical changes, but there are no sharp changes at the gel point. Evidence from infrared spectroscopy (Wilson Mesley, 1968) and electron probe microanalysis (Kent, Fletcher Wilson, 1970 Wilson et al, 1972) indicates that the main reaction product is an amorphous aluminophosphate. Also formed in the matrix were fluorite (CaF ) and sodium acid phosphates. 

At present there is no more than indirect evidence for the existence of the halogeno-halothiophosphoric acids and the dibromo compound. So the unsoluble nitron dibromo-phosphate precipitates in case of the partial hydrolysis of POBr3 in acetone and in presence of nitron (5). Further the partial hydrolysis of PSCI3 and PSCI2F in presence of big cations, such as tetraphenylphosphonium or -arsonium yields stable salts (22), which suggests the primary formation of the free acid in the solution ... 

Patients with tumor lysis syndrome experience a wide range of metabolic abnormalities. The massive cell lysis that occurs leads to the release of intracellular electrolytes, resulting in hyperkalemia and hyperphosphatemia. High concentrations of phosphate bind to calcium, leading to hypocalcemia and calcium phosphate precipitation in the renal tubule. Purine nucleic acids are also released that are subsequently metabolized to uric acid... 

Electrolyte disturbances that develop in patients with tumor lysis syndrome should be managed aggressively to avoid renal failure from hyperphosphatemia and hypocalcemia and cardiac signs from hyperkalemia. One exception pertains to the use of intravenous calcium for hypocalcemia. Adding calcium may cause further calcium phosphate precipitation in the presence of hyperphosphatemia and should be used cautiously. 

The Food and Drug Administration (FDA) published a safety alert in 1994 in response to two deaths associated with calcium-phosphate precipitation in PN.16 Autopsy reports from these patients revealed diffuse micro vascular pulmonary emboli containing calcium-phosphate precipitates. Because calcium and phosphate can bind and precipitate in solution, caution must be exercised when mixing these two electrolytes in PN admixtures. Several factors can affect calcium-phosphate solubility, including... 

Amino acid concentration. Primary factor that affects pH of the PN admixture the higher the concentration of amino acids, the higher is the amount of calcium and phosphate that can remain in solution (phosphate likely binds with amino acids and less is available to bind with calcium), therefore lowering the risk of calcium-phosphate precipitation. 

Time. More calcium and phosphate will dissociate over time, increasing the risk for calcium-phosphate precipitation. 

Temperature. As temperature increases, more calcium and phosphate dissociate and increase the risk of calcium-phosphate precipitation. 

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