Phosphate stabilization mineral reaction products

Table 7. Identified phosphate mineral reaction products in phosphate-stabilized AfS lV dry scrubber residues... 

In most applications, a small amount of binder powders is mixed with a large volume of inexpensive hllers and then the entire mixture is stirred in water to form the reaction slurry. For example, if the phosphate binders are used for manufacturing construction products, invariably the hllers are sand, gravel, ash, soil, or some mineral waste. The phosphate binders provide adhesion between the particles of these hllers and bind them into a solid object. Thus, these mixtures mimic conventional concrete mixmres in which Portland cement binder is mixed with large volume of sand and gravel to produce cement concrete. When phosphate binders are used, the products may be termed as phosphate concrete . In waste stabilization, the waste itself becomes the hller and the hnal product is termed as a waste form . 

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. 

The mineral nutrient elements take part in many processes. Interestingly enough, most elements are involved simultaneously in different reactions of metabolism. Thus, P, K, Mg, Ca, and B are important for the formation of nucleic acids, production of nucleotide phosphates, energy metabolism, and stabilization of membrane structures. Zn is a component of many different enzyme processes, and even Mn and Fe are involved in various reactions. Therefore, no clear assignment of individual elements to distinct areas of metabolism is possible. Indeed, results obtained with different vege-... 

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