Organophosphorus acids metal complexes

Both carboxylic (e.g., Versatic acid) and organophosphorus acids have been used commercially to extract the lanthanides. The extraction follows the formation of the metal-extractant complex [Eq. (11.21)] and so depends on the pH of the feed. 

Nieuwenhuizen and Harteveld [92] have realized a nerve agent dosimeter gas sensor based on the strong interaction between certain metal ions and organophosphorus compounds. In this case, the sensor material contains La(III) 2-bis(carboxymethyl)amino hexadecanoic acid and different factors such as humidity, concentration and layer thickness have been studied and optimized. Using a combination of a metallic complex with a molecular-imprinted polymer, a very sensitive sensor was developed for the detection of soman, a chemical warfare agent (the detection limit was 7 ppt) [93]. The biosensing material is based on a polymer coated onto a fiber-optic probe modified with a luminescent europium detection complex. This complex was... 

Metal-complexation/SFE using carbon dioxide has been successfully demonstrated for removal of lanthanides, actinides and various other fission products from solids and liquids (8-18), Direct dissolution of recalcitrant uranium oxides using nitric acid and metal-complexing agents in supercritical fluid carbon dioxide has also been reported (79-25). In this paper we explored supercritical fluid extraction of sorbed plutonium and americium from soil using common organophosphorus and beta-diketone complexants. We also qualitatively characterize actinide sorption to various soil fractions via use of sequential chemical extraction techniques. 

Gel-immobilized catalytic systems (GCS) represent swelled polymer composites in which active sites of the particular metal complex are inunobilized. Graft copolymers of ethylene-propylene rubber (EPRu) and ligands of 4-vinylpyridine, acrylic acid, vinylpyrrolidone, organophosphorus compounds etc. act as a polymeric supports (polymeric phases) [140]. The structure of metal complex sites immobilized in a polymer gel is presented by the following scheme ... 

The metal complexes formed by the anionic organophosphorus extractants are, on the other hand, very soluble in organic solvents. Such compounds have therefore been used for various technical processes. Most important is the monobasic diethylhexylphosphoric acid (HDEHP), but dibutylphosphoric acid (DBP) has also been widely applied [103,155]. Some data illustrating the properties of these extractants are collected in Table 21.19. 

Though the stripping of metal ions seemed to be feasible by an acid solution, the disadvantages in this case were the low solubility of PC-88A and the metal complexes in the ILs. This is also true with another organophosphorus extractant di(2-ethylhexyl)phosphoric acid (DEHPA) [12]. To develop a more practical IL-based extraction system, a new proton dissociation-type extractant, which is soluble in ILs like neutral extractants, was desired. 

Applications. A biotinylated GOX-based biosensor was developed based on a new electropolymerized material consisting of a pol3rp3uidyl complex of ruthenium(II) functionalized with a pyrrole group [90]. Because histidine, lysine and arginine functions also coordinate Os /Os , biosensors based on co-electrodeposited GOX, HRP, soybean peroxidase (SBP) and laccase with redox Os /Os polymer have been developed [89]. A metal chelate formed by nickel and nitrilotriacetic acid was used to modify a screen-printed electrode surface. The functionalized support allowed stable attachment of acetylcholinesterase and the resulting biosensor was used for sensitive detection of organophosphorus insecticides [91]. This method is attractive because it ensures a controlled and oriented enzyme immobilization, considerably improving the sensitivity and the detection limit. 

A method is being developed to transform actinide ions in the near surface environment to less soluble, less reactive, thermodynamically stable phosphate minerals phases through application of organophosphorus complexants. These complexants decompose slowly, releasing phosphate to promote the formation of stable phosphate mineral phases, particularly with the more soluble trivalent, pentavalent, and hexavalent actinide ions. The complexant of choice, myo-inositol(hexakisphosphoric acid) or phytic acid, is a natural product widely used as a nutritional supplement. We have determined that phytic acid decomposes slowly in the absence of microbiological effects, that crystalline phosphate minerals are formed as a consequence of its decomposition, and that the formation of actinide (lanthanide) phosphates reduces the solubility of trivalent and hexavalent metal ions under environmental conditions. 

Neuman RD, Nai-Fu-Zhou WuJ, Jons MA, Gaonkar AG, General model for aggregation of metal-extractant complexes in acidic organophosphorus solvent extraction systems. Sep. Sci. Technol. 1990 25(13-15), 1655-1674. 

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