Polyphosphates from Solution

Long-chain alkali metal polyphosphates seldom, if ever, crystallize when salted out of aqueous solutions. Knotting and coiling is probably a factor in this behavior. The anions are too irregular to fit into a crystal lattice and POP linkages are not being broken and reformed as they are in a melt. As noted earlier, all polyphosphates we tested could be crystallized from aqueous solution as the acridinium salts. Here stearic hindrance, caused by the very large flat cations. 

Unlike plant and animal kingdoms, very few mineral substances, such as sand, chert, stones, soil, clays, etc., are naturally fibrous. For this reason it is surprising to learn that properties usually associated with vegetable or animal matter are found in minerals. Moreover, these minerals can have properties so foreign to vegetable matter that they seem almost magical. Most of them will not burn Most resist high 

The attempt to cause a new system to crystallize with a morphology similar to chrysotile is a humbling experience. It is soon recognized that it is beyond all knowledge to cause a second system to crystallize as tiny rolls similar to rolled newspapers, but 200 angstroms in diameter and several centimeters long. All that any experimenter can do is adjust several variables, such as temperature, pressure, electrical or magnetic fields, radiation, composition, seeds, and prayer. If fibers form, it is merely a result of systems that are still too complicated to impose dictated results. 

As a footnote, I left this project not because we were failing to make as much progress as I felt we should have been making, but for personal reasons related to potential jeopardy to my family. In the event we were commercially successful. The phosphate fiber project justified my actions. 

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Polyphosphates are also an important class of organophosphorus polymers. In addition to their flame-retardant characteristics, they possess attractive plasticizing properties and can be used as polymeric additives to other polymers [123-128]. In general, polyphosphates can be prepared by interfacial [119,129], melt [130], or solution polycondensation [131,132a,b]. Kricheldorf and Koziel [133] prepared polyphosphates from silylated bisphenols. 

The most popular scheme by which solution-type fertilizers are made from low-conversion, wet-process superphosphoric acid is outlined in Fig. 24.20. The first step is ammoniation of the acid to produce ammonium polyphosphate base solution. By carrying out this ammoniation in a pipe reactor, a temperature of over 200°C is developed, which promotes an increase in polyphosphate content to 65-70 percent of total P2Os in the ammoni-ated acid.39,40 The grade of the resultant base is usually 10-34-0 an 11-37-0 grade can be made, but its storage properties are not as... 

Therefore, bacteria take up phosphate from solution and store it in the form of polyphosphate. Phosphate is removed as the excess organisms are separated from the system. These organisms, with the phosphate they contain, are added to and treated with the raw sludge, ultimately producing a treated sludge product richer in nutrients. 

It has been claimed that long chain ammonium polyphosphates can be treated with potassium hydroxide to form long chain polyphosphates that crystallize from solution as the dihydrate. It was suggested that the phosphate was a Kurrol s salt, but only after the salt... 

Tables XX and XXI it is evident that the fractional precipitation of polyphosphates from a mixed solution with silver nitrate precipitates polyphosphates of shorter chain lengths in earlier stages, and those of longer chain lengths in later stages.

For the clean-up of galvanic water, grafting polyphosphates on to the edges of kaolinite, metakaolinite, and Al (hydr)oxides greatly increases the capacities of these materials to remove Ni ", Co " and Cr from solutions through the formation of complexes with the phosphate groups (Tarasevich and Klimova, 2001). 

Sequestration is an important property of condensed phosphates and their ability to form soluble complexes with multivalent cations.Many studies have been made of this property. Condensed phosphates, primarily polyphosphates, differ from orthophosphates in the ways they interact with metal ions in aqueous solutions. Orthophosphates remove metal ions from solution by forming insoluble precipitates. They have been used for many years to soften water by precipitating calcium, magnesium, iron, etc. from solutions, but leaving a powdered precipitate that is usually undesirable. 

Polyphosphates do not precipitate metal ions from solution, but hold them in solution as soluble complexes, provided the ratio of cations to phosphates does not exceed some value related to a metastable solubility product. It should be obvious that a true solubility product does not exist for the same reasons a true solubility does not exist. If polyphosphates become overwhelmed, a precipitate will form and condensed phosphates function as orthophosphates in removing metal ions from solution. Rather than attempting to include an in-depth study of complexing agents and stability constants, a general statement will be made and readers are referred to published literature for a more comprehensive view. Perhaps the most perplexing issue about complexing, and equilibrium constants used to study and represent it, is the number of different constants used to represent a system. 

Fig. 11.22. TVA pipe reactor system for production of ammonium polyphosphate base solution from low-conversion superphosphoric acid. The product base solution is typically 10-34-0 with a 65-70% poly level. (Courtesy TVA.)...

Orthophosphate Hquid mixtures are ineffective as micronuttient carriers because of the formation of metal ammonium phosphates such as ZnNH PO. However, micronutrients are much more soluble in ammonium phosphate solutions in which a substantial proportion of the phosphoms is polyphosphate. The greater solubiHty results from the sequestering action of the polyphosphate. The amounts of Zn, Mn, Cu, and Fe soluble in base solution with 70% of its P as polyphosphate are 10 to 60 times their solubiHties in ammonium orthophosphate solution. When a mixture of several micronutrients is added to the same solution, the solubiHty of the individual metals is lowered significantly. In such mixtures the total micronuttient content should not exceed 3% and the storage time before precipitates appear may be much shorter than when only one micronuttient is present. 

Sugama, T. Kukacka, L. E. (1983b). Characteristics of magnesium polyphosphate cements derived from ammonium polyphosphate solutions. Cement Concrete Research, 13, 499-506. 

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