Organophosphorus acids base metals

Solvent extraction of base metals by organophosphorus acids 792... 

The use of organophosphorus acids, such as di(2-ethylhexyl)phosphoric acid (D2EHPA di(2-ethylhexyl) monohydrogen phosphate 2 R = C4H9CH(Et)CH2), is now well established in the recovery of base metals. This reagent has found commercial application in the separation of cobalt from nickel,67 68 the separation of zinc from impurities such as copper and cadmium,69 the recovery of uranium,68 beryllium70 and vanadium,71 and in separations involving yttrium and the rare-earth metals.72 73... 

Figure 5.11 shows the pH dependence of extraction of organophosphorus acids for common base metal ions. In general, the extraction of a particular ion shifts to higher pH in the order phosphoric phosphonic phosphinic (i.e., the extractants are weaker). It is also significant that the order of extraction changes as well. In par-ticnlar, the positions of Ca and Mg relative to base-metal cations should be noted. 

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. 

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... 

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. 

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