Phosphate insoluble

Na2C03 851 Ft For silicates, and silica-containing samples alumina-containing samples insoluble phosphates and sulfates... 

A rather more specific mechanism of microbial immobilization of metal ions is represented by the accumulation of uranium as an extracellular precipitate of hydrogen uranyl phosphate by a Citrobacter species (83). Staggering amounts of uranium can be precipitated more than 900% of the bacterial dry weight Recent work has shown that even elements that do not readily form insoluble phosphates, such as nickel and neptunium, may be incorporated into the uranyl phosphate crystallites (84). The precipitation is driven by the production of phosphate ions at the cell surface by an external phosphatase. 

In the double-neutralization process, Na2SiFg is precipitated and removed by filtration at a pH of 3—4 (9). Upon raising the pH to 7—9, insoluble phosphates of Fe, Al, Ca, and Mg form and separate. Iron can be precipitated as hydrous ferric oxide, reducing the phosphate loss at the second filter cake. Both the fluorosihcate and metal phosphate filter residues tend to be voluminous cakes that shrink when dewatered recovery of soluble phosphates trapped within the cakes is difficult. 

Trisodium phosphate is strongly alkaline many of its appHcations depend on this property. For example, many heavy-duty cleaning compositions contain trisodium phosphate as a primary alkalinity source. The crystalline dodecahydrate itself is marketed as a cleaning compound and paint remover. Traditionally, trisodium phosphate has been used in water softening to remove polyvalent metal ions by precipitation as insoluble phosphates. Because the hypochlorite complex of trisodium phosphate provides solutions that are strongly alkaline and contain active chlorine, it is used in disinfectant cleaners, scouring powders, and automatic dishwashing formulations. 

The relation between free phosphoric acid content and total phosphate content in a processing bath, whether based on iron, manganese or zinc, is very important this relation is generally referred to as the acid ratio. An excess of free acid will retard the dissociation of the primary and secondary phosphates and hinder the deposition of the tertiary phosphate coating sometimes excessive loss of metal takes place and the coating is loose and powdery. When the free acid content is too low, dissociation of phosphates (equations 15.2, 15.3 and 15.4) takes place in the solution as well as at the metal/solution interface and leads to precipitation of insoluble phosphates as sludge. The free acid content is usually determined by titrating with sodium... 

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. 

Where phosphate is used for internal treatment programs, a variety of insoluble phosphate and hydroxide salts are produced to form sludges. If these sludges are not properly held in a suspension by the use of appropriate polymeric dispersants (and then blown down from the boiler within a certain period), they will deposit on heat exchange surfaces as hard, adherent scales. 

Holzbecker and Ryan [825] determined these elements in seawater by neutron activation analysis after coprecipitation with lead phosphate. Lead phosphate gives no intense activities on irradiation, so it is a suitable matrix for trace metal determinations by neutron activation analysis. Precipitation of lead phosphate also brings down quantitatively the insoluble phosphates of silver (I), cadmium (II), chromium (III), copper (II), manganese (II), thorium (IV), uranium (VI), and zirconium (IV). Detection limits for each of these are given, and thorium and uranium determinations are described in detail. Gamma activity from 204Pb makes a useful internal standard to correct for geometry differences between samples, which for the lowest detection limits are counted close to the detector. 

Phosphate reacts and forms insoluble compounds with many metals, particularly iron, aluminum, and calcium. Under acid soil conditions, both iron and aluminum become more soluble, and thus as soil pH decreases, its phosphate fixing power increases. This means that iron and aluminum react with phosphate to form insoluble species that are not available to plants. Under basic conditions, high concentrations of calcium exist and insoluble calcium phosphates form. Insoluble phosphate species are also formed with other metals that happen to be present however, the three mentioned are generally present in the highest concentration, and so they represent the major reactants with phosphate. Iron, aluminum, and calcium phosphates can also occur as coatings on soil particles. 

The data presented in this paper indicate that excess levels (0.75%) of dietary zinc result in decreases in the bioavailability of calcium and phosphorus in rats and interfere with normal bone mineralization. High dietary levels of calcium or zinc appeared to cause a shift in the excretion of phosphorus from the urine to the feces, while the presence of extra phosphorus tended to keep the pathway of phosphorus excretion via the urine. The presence of large amounts of phosphorus in the Intestinal tract due to high intakes of zinc would increase the possibility of the formation of insoluble phosphate salts with various cations, including calcium, which may be present. A shift in phosphorus excretion from the feces to the urine, however, could result in an environmental condition within the system which would tend to increase the bioavailability of cations to the animal. The adverse effect of zinc toxicity on calcium and phosphorus status of young rats could be alleviated with calcium and/or phosphorus supplements. 

Wet Process Phosphoric Acid. A production process flow diagram is shown in Figure 8. Insoluble phosphate rock is changed to water-soluble phosphoric acid by solubilizing the phosphate rock with an acid, generally sulfuric or nitric. The phosphoric acid produced from the nitric acid process is blended with other ingredients to produce a fertilizer, whereas the phosphoric acid produced from the sulfuric acid process must be concentrated before further use. Minor quantities of fluorine, iron, aluminum, sUica, and uranium are usually the most serious waste effluent problems. 

The methods of analysis for phosphate solubility are not absolute, but empirical that is, they are based on practical experience. For example, the neutral ammonium citrate method is favoured in the USA because it has received over 100 years of study and experimentation, and provides an index correlating the laboratory results with the fertilizing value of water-insoluble phosphates under the conditions prevailing in the principal farming regions of the country. The particular solvent is therefore not an attempt to accurately reproduce the properties of the soil solution in the immediate vicinity of the... 

Fig. 1. Schematic of chemical stabilization principle. Soluble phases are converted to insoluble phosphate minerals.

Na2C03 Pt For dissolving silicates (clays, rocks, minerals, glasses), refractory oxides, insoluble phosphates, and sulfates. 

Acid-soluble and acid-insoluble phosphates in ChloreUa vulgaris increased 2 to 4 fold, depending on the concentration of trichioroacetate, with the soluble phosphorus most affected. However, neither respiration nor the carbohydrate-metabolizing enzymes were particularly sensitive. Little change occurred in the hydrolyzable polysaccharides.168... 

However, even simple antacid therapy can have unlooked-for effects. Thus, because of the formation of insoluble phosphates, prolonged use of antacids (excepting aluminium or calcium phosphate) can lead to hypophosphataemia and a compensating increase in calcium absorption or mobilisation from bone4. ... 

Treatments of diseases such as osteoporosis, rickets and osteomalacia, in which there is a disturbance of phosphate levels, is complicated by the interdependence of calcium metabolism. This topic has recently been discussed in relation to clinical medicine21. There is the further difficulty that absorption of phosphate from the bowel can be decreased in the presence of calcium or aluminium salts because of the formation of their insoluble phosphates. Uptake of phosphate by bone is exploited in the treatment of polycythaemia vera by intravenous injection of 32P as sodium phosphate. The resulting irradiation of the neighbouring red bone marrow diminishes the production of red cells. 

The phloem tubes consist of adapted cells that transport the products of photosynthesis, and other compounds such as growth regulators, to the growing parts of the plant including the roots. Since phosphate concentration in the phloem is high, those elements with insoluble phosphates are not usually transported in the phloem. Na+, K+, Rb +, Cs+ and Mg2+ are easily transported, whereas, Pb2+, Ca2+, Sr2+ and Ba2+ are not. 

With Molybdate.—Precipitation of phosphate in nitric acid solution by means of ammonium molybdate serves not only as a qualitative test, but also for the quantitative separation of phosphate in a preliminary or even final manner. Insoluble phosphates are previously dissolved in nitric acid, while the phosphoric acids are nearly neutralised with ammonia and then acidified with nitric acid. The nitric acid solution of ammonium molybdate (8 per cent.) is added hot, the mixture boiled and the precipitate collected on a filter. The precipitate may now be treated in various ways... 

Sodium phosphate solution white precipitate of zirconium phosphate, Zr(HP04)2 or Zr0(H2P04)2, even in solutions containing 10 per cent sulphuric acid by weight and also tartrates and citrates. No other element forms an insoluble phosphate under these conditions except titanium. The latter element can be kept in solution as peroxotitanic acid by the addition of sufficient hydrogen peroxide solution, preferably of 100-volume strength, before the sodium phosphate is introduced. 

Orthophosphoric acid and phosphates form complexes with many transition metal ions. The precipitation of insoluble phosphates from fairly concentrated acid solution (3-6 M HNO3) is characteristic of 4+ cations such as those of Ce, Th, Zr, U, and Pu. Phosphates of B, Al, Zr, and so on, are used industrially as catalysts for a variety of reactions. The phosphate ions, H2PO4, HPO4, and POJ are well known as ligands, of monodentate, chelating, or bridging types examples of the last two are... 

In the phosphate washing discussed above, only a small amount of acid phosphate is used to convert contaminants into their insoluble phosphate forms. To fabricate CBPC waste forms, however, a larger amount of binder is needed, so compared to the phosphate washing, the cost of the binder is high. This condition does not mean that the volume of the stabilized waste will increase. Typically, the washed waste is loosely packed, but the fully stabilized ceramic matrix is dense. As a result, the volume does not increase and, hence, the disposal cost will remain the same. Depending on the nature of the waste and amount of the phosphate binder used, the binder cost may be the only higher cost in the CBPC treatment compared to simple acid washing. 

Most waste streams contain more than one contaminant. Some may have contaminants such as Hg, whose sulfide has a higher pAQp than its phosphate, and Ba, whose sulfide is soluble, but phosphate is insoluble. Even in these cases, sulfide treatment followed by phosphate ceramic formation is very effective. The sulfide treatment will produce insoluble HgS that will be microencapsulated in the phosphate matrix, but Ba will be converted partially into soluble BaS, which subsequently will dissolve and will be converted to insoluble phosphate in the CBPC matrix. Thus, the dual treatment is very effective even when several contaminants with varying solubility of sulfides and phosphates are found in the same waste. 

As discussed in Chapter 16, chemical stabilization is a result of conversion of contaminants in a radioactive waste into their insoluble phosphate forms. This conversion is solely dependent on the dissolution kinetics of these components. In general, if these components are in a soluble or even in a sparsely soluble form, they will dissolve in the initially acidic CBPC slurry and react with the phosphate anions. The resultant product will be an insoluble phosphate that will not leach into the groundwater. On the other hand, if a certain radioactive component is not soluble in the acid slurry, it will not be soluble in more neutral groundwater, because the solubility of such components is lower in neutral than in acidic solutions. Such a component will be simply microencapsulated in the phosphate matrix of the CBPC. Thus, the solubility of hazardous and radioactive components is key to chemical immobilization. 

Worldwide, given adequate nutrients, the presence of AP+ is the main limiting factor in plant productivity in acidic soils. Plants such as tea that accumulate AP+ are rare and do so in acidic soils and evidently detoxify the AP+ by storing a chelated version in cell vacuoles of older leaves separate from the more metabolically active parts of the plant. Tea plants have been found with as much as 3% AP+ in older leaves and only 0.01% in younger ones, a 300-fold difference. Typical tea infusions contain about 50 times as much AP+ as do infusions from coffee. Adding milk to tea should immobilize Al + as an insoluble phosphate, while lemon will strongly complex the Al + in deleterious soluble citrate complexes described below. 

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