Metals phosphate stabilization

In France, a number of researchers have explored the washing, phosphate stabilization, and sintering or calcination of residues (Derie 1996 Iretskya et al. 1999 Nzihou Sharrock 2002 Piantone et al. 2003). The formation of more crystalline hydroxyapatite reaction products helps reduce leachability of metals incor-... 

STABCAL was also used to construct pE-pH stability fields for chloropyromorphite, hinsdalite, plumbogummite, tricadmium diphosphate, tricopper diphosphate, and hopeite (Fig. 7). These diagrams allow for estimation of stability with respect to pH and to the presence of insoluble sulphides. The NBS thermodynamic database (Wagman et al. 1982) was used as a source of thermodynamic data. The total concentrations chosen for each metal were selected to produce a stability region for the metal phosphate solid. In some cases, this was a very low total concentration (e.g., CTPb =1 x 10 10 M for Pb). In other cases, the total metals concentration was high (e.g., C r.cd— 1 x 10 3 M for Cd). The modelling exercise used typical equilibrium concentrations for MSW bottom ash leachates as shown in Table 2. 

Phosphate is widely used as a chemical stabilization agent for MSW combustion residues in Japan and North America and is under consideration for use in parts of Europe. The application of this technology to MSW ashes generally parallels its application to contaminated soils. Metal phosphates (notably Cd, Cu, Pb and Zn) frequently have wide pH distribution, pH-pE predominance, and redox stability within complex ash pore water systems. Stabilization mechanisms identified in other contaminated systems (e.g., soils), involving a combination of sorption, heterogeneous nucleation, and surface precipitation, or solution-phase precipitation are generally observed in ash systems. 

Crannell, B. S., Eighmy, T. T., Krzanowski, J. R. Eusden, J. D. Jr. 1999. Phosphate stabilization mechanisms for heavy metals in electric arc furnace smelter dusts. In Nikolaidis, N., Erkey, C. Smets, B. (eds) Hazardous Wastes and Hazardous Materials. Technomic Publishing, Lancaster, Pennsylvania, 561-570. 

Nriagu, J. O. 1984. Formation and stability of base metal phosphates in soils and sediments. In Nriagu, J. O. Moore, P. B. (eds) Phosphate Minerals. Springer-Verlag, Berlin, 318-329. 

Polynucleotide polymerases, or nucleotidyl transferases, are enzymes that catalyze the template-instructed polymerization of deoxyribo- or ribonu-cleoside triphosphates into polymeric nucleic acid - DNA or RNA. Depending on their substrate specificity, polymerases are classed as RNA- or DNA-dependent polymerases which copy their templates into RNA or DNA (all combinations of substrates are possible). Polymerization, or nucleotidyl transfer, involves formation of a phosphodiester bond that results from nucleophilic attack of the 3 -OH of primer-template on the a-phosphate group of the incoming nucleoside triphosphate. Although substantial diversity of sequence and function is observed for natural polymerases, there is evidence that many employ the same mechanism for DNA or RNA synthesis. On the basis of the crystal structures of polymerase replication complexes, a two-metal-ion mechanism of nucleotide addition was proposed [1] during this two divalent metal ions stabilize the structure and charge of the expected pentacovalent transition state (Figure B.16.1). 

The hydrides phosphine PH3, arsine ASH3 and stibine SbH3 can be prepared by hydrolysis of metal phosphates, or by reduction of molecular compounds like PC13. They are very toxic gases, with decreasing thermal stability P > As > Sb. Unlike ammonia they are not basic in water. The hydrazine... 

Over the last decade, extensive research has been conducted on conversion of hazardous metals from different waste streams using phosphate stabilizers. Eighmy and Eusden [10] searched the literature on phosphate amendment of various industrial waste streams. They found 39 patents in this area since 1994. An updated summary of the various waste streams, either treated or tested by phosphate amendment or solidification, is given in Table 16.3. 

E. Tickanen and P. Turpin, Treatment of heavy metal-bearing wastes using a buffered phosphate stabilization system, in Proceedings of the 51st Industrial Waste Conference, eds. R. Wukasch and C. Dalton (CRC Press, Boca Raton, PL, 1997), pp. 627-635. 

Reversible electrochemical lithium deintercalation from 2D and 3D materials is important for applications in lithium-ion batteries. New developments have been realized in two classes of materials that show exceptionally promising properties as cathode materials. The first includes mixed layered oxides exemplified by LijMn Nij, Co ]02, where the Mn remains inert to oxidation/reduction and acts as a framework stabilizer while the other elements carry the redox load. Another class that shows much potential is metal phosphates, which includes olivine-type LiFeP04, and the NASICON-related frameworks Li3M2(P04)3. 

The first such consequence is to stabilize the ordered form of the nucleic acid molecule. In DNA this means that phosphate-binding metals will stabilize the double helix. It was discovered quite some time ago that, if DNA is dissolved in distilled water, the double helical structure is... 

In spite of their highly open structures, both materials may be synthesized without structure directing agents. Since most transition metal phosphates containing template molecules typically cannot be calcined without pore collapse, template-free synthesis appears to be the most promising direction for the formation of new porous materials. The exciting properties observed in the VSB family are likely glimpses of what may occur in other transition metal phosphate systems once thermal stability problems are overcome. 

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