Phosphate stabilization calcium minerals

The crystalline mineral in bones and teeth is generally regarded as an imperfect calcium hydroxyapatite. Apatite minerals, principally calcium fluorapatite, are both abundant and ubiquitous and are the principal source of phosphate for fertilizers. Their abundance is probably an expression of the very high affinity which calcium and phosphate ions have for each other so that it is perhaps not surprising that, on account of its stability, calcium hydroxyapatite has been selected to play an important part, both structurally and physiologically, in many living things. Ions other than calcium, phosphate and hydroxyl are present in the crystallites in which the atomic ratio of calcium to phosphorus departs considerably from the theoretical value of 1-67 (Table 35.1). 

Physical Form, brown to black oily liquid new mineral-based crankcase oil contains petrochemicals (straight-chain hydrocarbons, aromatic hydrocarbons, and polyaromatic hydrocarbons or PAH) plus stabilizers and detergents including zinc dithiophosphate, zinc diaryl or dialkyl dithiophosphates (ZTDP), calcium alkyl phenates, magnesium, sodium, and calcium sulfonates, tricresyl phosphates, molybdenum disulfide, heavy metal soaps, cadmium, and zinc. ... 

Monobasic calcium phosphate is primarily used in fertilizers. It also is used in baking powders as a mineral supplement in food as a buffer for pH control and as a stabilizer for plastics. 

Apatite, a natural calcium fluoride phosphate, can adsorb low to moderate levels of dissolved metals from soils, groundwater, and waste streams. Metals naturally chemically bind to the apatite, forming extremely stable phosphate phases of metal-substituted apatite minerals. This natural process is used by UFA Ventures, Inc., and is called phosphate-induced metals stabilization (PIMS). The PIMS material can by used in a packed bed, mixed with the contaminated media, or used as a permeable barrier. The material may be left in place, disposed of, or reused. It requires no further treatment or stabilization. Research is currently being conducted on using apatite to remediate soil and groundwater contaminated with heavy metals, and the technology may also be applicable to radionuclides. The technology is not yet commercially available. 

It is necessary to adjust the Ca, Mg, phosphate, and citrate content of the concentrate to control aggregation and precipitation of the proteins and minerals during sterilization. By controlling protein aggregation, this adjustment provides optimum viscosity to stabilize the protein, mineral, and milk fat emulsion systems during prolonged storage of the sterile product. Some milk concentrates are stabilized by addition of Ca and Mg salts, whereas others are stabilized by addition of phosphate or citrate salts (Parry, 1974). Chemical compounds approved for addition to evaporated milk include calcium chloride, sodium citrate, and disodium phosphate (CFR 1982). 

The tri-calcium, barium, and strontium phosphates are members of an isostructural series M3(P04)2, where M = Ca, Ba, Sr, etc. The minerals formed by Ca are very important in bioceramics, and because Ba and Sr are fission products (i.e., formed as by-products in nuclear reactions), apatite minerals play a major role in their stabilization for disposal (see Chapter 17). Within these common structures, however, calcium phosphate goes through several phase changes at different temperatures. These phases are labeled as (3, a, a, etc. The reader is referred to Refs. [1,2] for details. 

Evidence for the importance of mineral-protein equilibria was seen by comparing the heat stability-pH profiles of concentrated milk with added EDTA or phosphates. Although EDTA caused a similar reduction of the activity in recombined concentrated milks compared to those with added phosphate, milks with added EDTA had reduced heat stability. This was attributed to the difference in the level of colloidal calcium phosphate in micelles which changes the partitioning of the caseins... 

The interest in mineral fortification of milk for the production of milks with higher nutritional value is a challenge. This is because the introduction of minerals upsets the mineral-protein equilibria in milk which will affect their stability. Philippe et al. (2004) showed that supplementation of skim milk with calcium gluconate, calcium lactate, or calcium chloride (up to 16 mmole added Ca/kg) decreased the heat stability. The addition of MgCl2 or FeCla (at a level of 8 mmole/kg) also reduced the heat stability of casein micelles (Philippe et al., 2005). However, by manipulating the mineral equilibria of milk with the use of a combination of soluble calcium salts and orthophosphates, it is possible to produce milks (with up to 20 mmole added Ca/kg) that are stable to heating (Williams et al., 2005). O Kennedy et al. (2001) showed that denatured whey proteins could be used as a carrier for calcium phosphate and further that adequate heat stability at 130 °C of whey protein-calcium phosphate suspensions could be achieved by appropriate adjustment of pH. 

The elements form an enormous range of compounds with oxoanions, many of those with calcium (carbonate, silicate, phosphate, sulfate) being common minerals in the Earth s crust. Hydrated forms are common. Their thermal stability towards decomposition to the oxide is less than that for the alkali metals, and increases with cation size. Thus Be (like Al) does not form a stable carbonate the decomposition temperatures for the others range from 400°C for MgC03 to 1400°C for BaC03. 

Each form of calcium phosphate has its own uses. The dibasic form is used as a nutrient and mineral supplement in animal foods and in certain processed foods, especially cereals. In addition to its nutritional value, dibasic calcium phosphate acts as a dough conditioner, stabilizer, and thickener in foods. The compound is also used in dental products to provide replacement for hydroxyapatite lost to decay or other factors. 

Nriagu JO (1984) Formation and stability of base metal phosphates in soils and sediments. In Phosphate Minerals. Nriagu JO, Moore PB (eds) Springer-Verlag, New York, p. 318-329 Oberti R, Ottolini L, Della Ventura G, Pardon GC (2001) On the symmetiy and crystal chemistiy of britholite New stmctural and microanalytical data. Am Mineral 86 1066-1075 Ohkubo Y (1968) EPR spectra of manganese(II) ions in synthetic calcium chloride fluoride phosphates. J Appl Phys 39 5344-5345... 

Serret A, Cabanas MV, Vallet-Regi M (2000) Stabilization of calcium oxyapatites with lanthanum(lll)-created anionic vacancies. Chem Mater 12 3836-3841 Seiy A, Manceau A, Greaves GN (1996) Chemical state of Cd in apatite phosphate ores as determined by EXAFS spectroscopy. Am Mineral 81 864-873... 

In soils and sediments, complexation can increase organic phosphorus stabilization, especially with iron (III) and calcium ions and their minerals (Harrison, 1987 House and Denison, 2002). The interaction with iron (III) was reported to transform a large part of the labile and moderately labile organic phosphorus forms supplied with manure to paddy soils into more resistant organic phosphorus, possibly because inositol phosphates initially bound to calcium or magnesium were transformed into iron-bound compounds (Zhang et aL, 1994). In the presence of calcium, myo-inositol hexakisphosphate can form two soluble calcium complexes with one or two calcium ions (Ca - or Ca2-phytate), but when three calcium ions are involved (Cag-phytate), the complex precipitates at all pH values (Graf, 1983). This enhances the interaction of myo-... 

Lead immobilization by phosphates arises from the low solubility of pyromorphite (Pb5(P04)3Cl). As stated, lead members of the apatite group minerals are much less soluble than their calcium congeners. Nriagu [39], as early as 1974, proposed the removal of lead from wastewaters and the stabilization of lead in contaminated soils and sediments by reaction with phosphate ions to precipitate pyromorphite. 

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