Spiro D. Alexandratos

Polymer-supported reagents for the selective complexation of metal ions: an overview

Research from the current literature on various ligands that display different affinities toward metal ions will be summarized. Important ligands include heterocyclic amines, amidoximes, dithizone, hydroxamic acid, crown ethers, phenolics and phosphorus-based ligands.

Diphonix® Resin: A Review of Its Properties and Applications

Abstract The recently developed Diphonix® resin is a new multifunctional chelating ion exchange resin containing geminally substituted diphosphonic acid ligands chemically bonded to a styrene-based polymeric matrix. Diphonix can be regarded as a dual mechanism polymer, with a sulfonic acid cation exchange group allowing for rapid access, mostly non-specific, of ions into the polymeric network, and the diphosphonic acid group responsible for specificity (recognition) for a number of metal cations. The Diphonix resin exhibits an extraordinarily strong affinity for actinides, especially in the tetra- and hexavalent oxidation states. Therefore the resin has potential for applications in TRU and mixed waste treatment and characterization, and in the development of new procedures for rapid actinide preconcentration and separation from environmental samples. Metal uptake studies have been extended to alkaline earth cations, to transition and post-transition metal species, and to metal sorption from neutral or ne...

UPTAKE OF METAL IONS BY A NEW CHELATING ION-EXCHANGE RESIN. PART 1: ACID DEPENDENCIES OF ACTINIDE IONS*

ABSTRACT The uptake of several actinide ions [U(VI), Pu(IV), Np(IV), Th(IV] and Am(DI)) from nitric and hydrochloric acid solutions, and of U(VI) from near-neutral solutions by the new chelating ion-exchange resin, DiphonixTM, has been investigated. Diphonix is a polyfunctional resin containing sulfonic and gem-diphosphonic acid groups chemically bonded in a styrene-divinylbenzene polymeric network. Comparison of the acid dependencies of the actinide ions uptake measured with Diphonix with those obtained using a commercial sulfonic -type resin and a resin containing both sulfonic and monophosphonic aCid groups, hat Shown that Diphonix binds the actinides via a different kind of chemical interaction, involving the.formation of chelate complexes through the phosphoryl groups of the gem-diphosphonic acids. As a consequence, Diphonix is superior to other resins in extracting actinide ions from very acidic solutions. A better performance of Diphonix is also observed with the uptake of uranium from neutral solu...

UPTAKE OF METAL IONS BY A NEW CHELATING ION-EXCHANGE RESIN. PART 4 : KINETICS

Abstract The rate of uptake of several actinide ions [Am(III), U(VI), Th(IV), Np(IV) and Pu(IV)] and of some transition-metal ions [Co(II), Zn(II), Fe(III) and Cr(III)] at tracer concentration level, from solutions of various compositions, by the new chelating ion-exchange resin, DiphonixTm, has been investigated. Diphonix is a polyfunctional resin containing sulfonic and gem-diphosphonic acid groups chemically bonded in a styrene-divinylbenzene polymeric network. It binds actinide and other ions through the formation of chelate complexes with the phosphoryl groups of the gem-diphosphonic acids. The experiments discussed in this work have allowed us to establish the paramount importance of the presence of the sulfonic groups in obtaining practically useful rates of metal ions uptake. Comparison of the kinetic behavior of Diphonix with that of commercial sulfonic-type resins has shown that Diphonix reacts with the investigated ions as rapidly as do the other resins. Conditions for efficient and rapid strip...

Efficient Treatment of Perchlorate (ClO4 −)-Contaminated Groundwater with Bifunctional Anion Exchange Resins

The perchlorate (ClO4 −) anion originates as a contaminant in the environment primarily from the disposal of solid salts of ammonium or sodium perchlorate, which are very soluble in water.1,2 Although thermodynamically a strong oxidizing agent, the perchlorate anion is known to be kinetically inert in many redox reactions and noncomplexing in its interactions with typical metal ions found in the environment. These properties make the perchlorate ion exceedingly mobile in the subsurface soil environment. It can persist for many decades under typical groundwater and surface-water conditions because of kinetic barriers in its reactivity with other organic or inorganic constituents. Large volumes of perchlorate-containing compounds have been disposed of in the environment since the 1950s.1 However, the extent of the problem was not folly realized until 1997, shortly after the development of a sensitive ion Chromatographic method for detecting ClO4 − in water.3 A national survey indicates that 44 states have former perchlorate manufacturers or users; ClO4 − has now been detected in groundwater or surface water in 14 states.2 For example, water suppliers in California have detected ClO4 − in 144 public water-supply wells; 3 8 of these are above California’s advisory action level of 18 μg L−1 ClO4 −.

Functionalized polymer foams as metal ion chelating agents with rapid complexation kinetics

Foams prepared from vinylbenzyl chloride and crosslinked with divinylbenzene were functionalized with trialkylphosphite and tetralkylvinylidene diphosphonate. It was determined that the foams could be uniformly functionalized. Batch studies with the functionalized foams show that high levels of metal ion complexation can be achieved. Foams may therefore offer an important alternative to beads for rapid complexation reactions due to their highly porous structure.

ION-SELECTIVE POLYMER-SUPPORTED REAGENTS

ABSTRACT The design and synthesis of polymer-supported reagents that can selectively complex targeted metal ions from multi-component solutions will continue to be an important area of research into the 21st century. Environmental remediation and sensor technology are only two of a number of areas in which such polymers can be applied. This paper reviews the recent literature with an emphasis on the key ligands that have been immobilized in order to better understand where this research is heading in the near future.

Synthesis and characterization of a bifunctional ion exchange resin with polystyrene-immobilized diphosphonic acid ligands

A new ion exchange resin for the selective complexation of metal ions has been synthesized by functionalizing vinylbenzyl chloride-styrene-divinylbenzene copolymer beads with the sodium salt of tetra(isopropyl) methylene diphosphonate. The effects of bifunctionality, matrix rigidity, degree of functionalization, and macroporosity on final resin properties have been quantified. A sulfonic acid-diphosphonic acid bifunctional resin is highly selective with rapid complexation kinetics. A macroporous polymer matrix crosslinked with 10% divinylbenzene provides optimum results; for example, 99.7% Eu(III) is complexed from a 1M nitric acid solution with a 30-min contact time. The importance of physical crosslinking as well as chemical crosslinking in limiting access of substrates into polymer-supported reagents is discussed.

UPTAKE OF METAL IONS BY A NEW CHELATING ION EXCHANGE RESIN. PART 3: PROTONATION CONSTANTS VIA POTENTIOMETRIC TITRATION AND SOLID STATE 31P NMR SPECTROSCOPY

Abstract A new chelating ion exchange resin which incorporates methylenediphosphonate, carboxylate, and sulfonate functional groups in a polystyrene-divinylbenzene matrix has been prepared. This resin exhibits exceptionally high affinity for polyvalent cations even from moderately acidic aqueous media. Metal ion coordination occurs primarily at the diphosphonate group with the secondary binding sites contributing to charge neutralization when necessary and possible, and to increasing hydrophilicity of the resin pores. In the present investigation, the protonation equilibria of the phosphonate groups in the resin are investigated via potentiometric titration and solid-state 31P NMR spectroscopy of the resin. Intrinsic equilibrium constants for the first two diphosphonate protonation reactions are pk47equal; 10.47 and pK3 = 7.24. The last two protons added to the diphosphonate group are acidic having pKa values less than 2.5. These protonation constants are consistent with those reported previously for mono...

Synthesis and characterization of high-stability solvent-impregnated resins

A copolymer comprised of glycidyl methacrylate and N,N-methylenebis(acrylamide) has been defined that can be used to coat solvent-impregnated resins (SIRs). Vinyl groups on the surface of a cross-linked macroporous support were used to anchor the polar copolymer to the surface of the bead. The coated SIR containing di(2-ethylhexyl)phosphoric acid maintained a high level of metal ion complexation (96% Cu(II)) over five cycles while the uncoated SIR dropped from 93% to 11% Cu(II) complexed in three cycles.