Uses of phosphates

At the time phosphate fibers were abandoned, risk liability could surely be viewed as a rational consideration. It is now more than ten years since phosphate fibers were first announced. Recently ChemTech (September 1993) featured an article in which phosphate fibers were the first item cited as a substance of which society had been deprived, as a result of potential litigations. This was but one of dozens of articles and television programs and newspaper articles devoted to phosphate fibers in recent years. Multiple needs for these fibers still exist and the invention refuses to die. Phosphate fibers cannot be MW-invented. Judging from current literature, the Japanese are likely to be the first to market phosphate fibers as a new item of commerce and there is eveiy reason to believe it can be a very profitable product for them. 

As a backdrop for uses of phosphate fibers, perhaps it will be helpful to consider a few of the more important uses of phosphates that directly influence all our lives. Fertilizers have been mentioned numerous times. Little is to be gained by additional attention to fertilizers except to reiterate that, if we are to eat, we shall manufacture phosphate fertilizers in ever increasing quantities, if the population of Earth continues to expand. There is no choice  

No one has ever before questioned the need for phosphate detergents in industrial and institutional uses such as restaurants and hospitals, and particularly in automatic dishwashing machines for home use. Hypochlorites are almost universally used to clean tables and counters in restaurants to help us from becoming infected by bacteria left in the foods spilled by other customers. This week a detergent manufacturer is test-marketing a nonphosphate nonchlorine recycled box in a western city. The printing on the box highlights what the box does not contain. 

It will be interesting to learn how this product performs. If problems do not arise from bacteria left on dishes, it probably will be the first of a new class of green detergents for home use. 

It is almost, if not impossible to get funding for studies of improvements to our environment that come from the use of a product put into the environment. Can you think of one There are a few, and phosphates are again being added to lakes to increase fish production. It has finally been recognized that if fish are to eat they too must have phosphates. 

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Scale and deposits are controlled through the use of phosphates, chelants, and polymers. Phosphates are precipitating treatments, and chelants are solubilizing treatments. Polymers are most widely used to disperse particulates but they are also used to solubilize contaminants under certain conditions. 

The use of chlorinated trisodium phosphate is declining. It has been largely replaced by chlorinated isocyanurates in powdered abrasive cleansers and automatic dishwash detergents to reduce cost, improve performance, or comply with restrictions on the use of phosphates. Some chlorinated trisodium phosphate is stiU used in commercial laundries and in disinfectant cleaners. 

Precipitation and Vapor-Phase Inhibitors. Precipitation inhibitors are film-forming compounds that produce barrier films over the entire surface. Phosphates and siUcates, which are the most common, do not provide the degree of protection afforded by chromate inhibitors, but are useful in situations where nontoxic additives are required. Two main drawbacks to the use of phosphates and siUcates are the dependence on the water composition and the control required to achieve maximum inhibition (37,38). 

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. 

Phosphorus also occurs in all living things and the phosphate cycle, including the massive use of phosphatic fertilizers, is of great current interest.O 20) -pj.jg movement of phosphorus through the environment differs from that of the other non-metals essential to life (H, C, N, O and S) because it has no volatile compounds that can circulate via the atmosphere. Instead, it circulates via two rapid biological... 

Table 15.12 Typical uses of phosphate coatings on steel ...

Thesequenceof formulation types may be deduced fromp. 17 21 and may be summarised as high levels of chromate low levels, of chromate, but with polyphosphates further reductions in chromate by the introduction of zinc ions and polyphosphate instability overcome by the use of phosphates and... 

Phosphate conversion coatings provide a highly crystalline, electrically neutral bond between a base metal and paint film. The most widespread use of phosphate coatings is to prolong the useful life of paint finishes. Phosphate coatings are primarily used on steel and galvanized surfaces but can also be applied to aluminum. Basically, there are three types of phosphate coatings ... 

INCO-DC, International Cooperation with Developing Countries of the European Union (2001) Sustainable halophyte utilization in the mediterranean and subtropical dry regions. Final Report Jeger MJ (2000) Bottlenecks in IPM. Crop Prot 19 787-792 Kang WS (2001) Development of a flame weeder. Trans ASAE 44 1065-1070 Khasawneh FE, Doll EC (1978) The use of phosphate rock for direct application to soils. Adv Agron 30 159-203... 

Also known as lime-induced chlorosis, this may be caused by a soil pH that is too high for acid-loving plants, by waterlogging, or by excessive use of phosphate-rich fertilizers. 

Today, phosphoric acid for use in the pharmaceutical or food industry must be free from uranium and other harmful metals. In the future, the processing of phosphate rock for production of fertilizers may be an important source of uranium because uranium removal may become compulsory to avoid its dissemination into the environment from the use of phosphate-based fertilizers. 

Although chromate is the best aqueous corrosion inhibitor available, its use has been severely curtailed due to toxicity and environmental concerns ( ). One of the more successful non-chromate treatments involves the use of phosphate/phosphonate combinations. This treatment employs high levels of orthophosphate to promote passivation of the metal surfaces. Therefore, it is important to control calcium phosphate crystallization so that high levels of orthophosphate may be maintained in the system without fouling or impeding heat-transfer functions. 

The use of phosphate-free carbon to decolorize soil extracts has been found to give erratic results. 

The use of phosphate has been widely evaluated and subjected to field trials for Pb-contaminated soils. Most treatment systems involve excavation, pug milling of the soil with the stabilization agent, and either replacement or landfill disposal. Occasionally, for larger sites and deeper contamination, in situ mixing with large augers is used. 

Crannell, B. S., Eighmy, T. T., Butler, L., Emery, E. Cartledge, F. 2003a. Use of phosphate to stabilize heavy metals in contaminated sediments. In Pederson, J. Adams, E. (eds) Dredged Material Management Options and Environmental Concerns. MIT Sea Grant Publications, Cambridge, Massachusetts, 175-178. 

Khasawneh, F.E. and Doll, E.C. 1978. The use of phosphate rock for direct application to soils. Advances in Agronomy 3Q 159-206. 

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