Organic Anion Exchange Research Articles

Radio Analytical Nondestructive Technique in Performance Evaluation of Organic Base Ion Exchange Resins Purolite NRW-6000 and Duolite A-378

Nondestructive radioanalytical technique using short lived isotopes 131I and 82Br was used as tracers to study the kinetics of iodide and bromide ion-isotopic exchange reactions. The kinetic data so obtained was used to evaluate the performance of organic base anion exchange resins Purolite NRW-6000 and Duolite A-378. It was observed that for iodide ion-isotopic exchange reaction performed at 40.0 °C using 1.000 g of ion exchange resins and 0.003 mol/L labeled iodide ion solution, the values of specific reaction rate (min-1), amount of iodide ion exchanged (mmol), initial rate of iodide ion exchange (mmol/min) and log Kd were calculated as 0.332, 0.582, 0.193 and 16.2 respectively for Purolite NRW-6000 resin, which was higher than the respective values of 0.210, 0.421, 0.088 and 14.7 as that obtained for Duolite A-378 resins. Also at a constant temperature of 40.0 °C, as the concentration of labeled iodide ion solution increases from 0.001 mol/L to 0.004 mol/L, the percentage of iodide ions exchanged increases from 74.68% to 79.48% using Purolite NRW-6000 resins and from 52.30% to 58.90% using Duolite A-378 resins. The overall results indicate superior performance of Purolite NRW-6000 resins over Duolite A-378 resins under identical operational parameters. It is expected here that the present technique can be extended further for characterization of different ion exchange resins which will further help in the selection of those reins for the specific industrial application.

Radio Analytical Nondestructive Technique in Performance Evaluation of Organic Base Ion Exchange Resins Purolite NRW-6000 and Duolite A-378

Nondestructive radioanalytical technique using short lived isotopes 131I and 82Br was used as tracers to study the kinetics of iodide and bromide ion-isotopic exchange reactions. The kinetic data so obtained was used to evaluate the performance of organic base anion exchange resins Purolite NRW-6000 and Duolite A-378. It was observed that for iodide ion-isotopic exchange reaction performed at 40.0 °C using 1.000 g of ion exchange resins and 0.003 mol/L labeled iodide ion solution, the values of specific reaction rate (min-1), amount of iodide ion exchanged (mmol), initial rate of iodide ion exchange (mmol/min) and log Kd were calculated as 0.332, 0.582, 0.193 and 16.2 respectively for Purolite NRW-6000 resin, which was higher than the respective values of 0.210, 0.421, 0.088 and 14.7 as that obtained for Duolite A-378 resins. Also at a constant temperature of 40.0 °C, as the concentration of labeled iodide ion solution increases from 0.001 mol/L to 0.004 mol/L, the percentage of iodide ions exchanged increases from 74.68% to 79.48% using Purolite NRW-6000 resins and from 52.30% to 58.90% using Duolite A-378 resins. The overall results indicate superior performance of Purolite NRW-6000 resins over Duolite A-378 resins under identical operational parameters. It is expected here that the present technique can be extended further for characterization of different ion exchange resins which will further help in the selection of those reins for the specific industrial application.

Removal of chromium(VI) from aqueous solutions using a polyvinyl-chloride inclusion membrane: Experimental study and modelling

The present paper reports the use of a polymer inclusion membrane (PIM) prepared without addition of plasticizers as solid sorbent for the removal of Cr(VI) ions from aqueous solution simulating the real industrial effluents. The studied sorbent (PIM) contains 40% organic anion exchanger Aliquat 336 and a polymer matrix of 60% polyvinyl chloride (PVC). The influence of the Aliquat 336 content of the PIM, the contact time, the pH and the initial metal concentration in the aqueous solution on the Cr(VI) sorption process was analysed by using the batch extraction technique. The optimal PIM composition was found to be 40% Aliquat 336/60% PVC (w/w). This sorbent was further used for the kinetic, isotherm, desorption, reusability and selectivity studies. The sorption kinetics was well described by the pseudo-second order model (Ho), and the kinetic experiments confirm that the sorption process of Cr(VI) into the optimal non-plasticized PVC-based PIM is a chemisorption, which occurs through a “relay mechanism”. The adsorption isotherm was best fitted by the Sips equation, and the experimentally determined maximum sorption capacity of Cr(VI) into the 40% Aliquat 336/60% PVC PIM was found to be 0.978mmol/g (50.85mg/g). The retained metal ions can be desorbed by using 0.5M NaNO3, this desorption of metal ions occurring concomitantly with the PIM regeneration. The use of this less aggressive eluent permits the reuse of the same PIM for at least five consecutive sorption processes. Moreover, the optimal PIM possesses a high selectivity for Cr(VI) ions from mixtures with other metal ions and anions usually existing in the real industrial effluents.All these properties indicate that PIM with the composition 40% Aliquat 336/60% PVC has a potential to be used as solid sorbent for Cr(VI) ions. Another advantage is its lower price compared to the plasticized PIMs.

A novel polymer inclusion membrane applied in chromium (VI) separation from aqueous solutions

In the present work, we analyze the transport properties of a novel polymer inclusion membrane (PIM) containing a poly-vinyl chloride (PVC) polymer matrix and the organic anion exchanger Aliquat 336 as a specific carrier, without addition of plasticizers. The study was specifically focused on the transport properties of Cr(VI) in conditions simulating industrial wastewaters. We analyzed the impact of several parameters on the Cr(VI) transport process such as: the carrier content of the PIM, the pH, and the phases’ composition. We concluded that efficient transport processes occur through a PIM containing 40% Aliquat 336/60% PVC (w/w). The process is very fast and efficient for solutions of initial Cr(VI) concentration smaller than 10−3mol/L, in which nearly all of Cr(VI) is removed within 3h. The performed experiments prove that Cr(VI) transport through the membrane is a facilitated counter-transport process. The obtained results sustain that this novel non-plasticized membrane possesses enhanced transport properties towards other liquid membranes and plasticized PIMs previously reported as used for Cr(VI) transport. Additionally, it possesses an excellent reliability and a high selectivity for Cr(VI) from mixtures with other metal ions and anions existing in the real industrial effluents. The PIM characterization highlights the plasticizing role of the carrier Aliquat 336.

Production of low and high specific activity 64Cu in a reactor

Production of Copper-64 ( 64 Cu) by irradiating copper and zinc metals in a reactor was evaluated. Low specific activity 64 Cu can be easily produced using thermal neutrons via 63 Cu (n,c) 64 Cu reaction, while use of fast neutrons are mandatory for high specific activity 64 Cu via 64 Zn (n,p) 64 Cu reaction. Natural copper and zinc targets were irradiated in Pakistan Research Reactor-1. Radionu- clidic impurities produced by thermal and fast neutrons were determined. Commonly available organic anion exchange resin (AG 1-X8) was used for the separation of no-carrier-added radiocopper from neutron irradiated zinc. More than 95% 64,67 Cu was recovered. The radionuclidic and chemical purity of 64 Cu was determined. The specific activity of 64 Cu produced by 63 Cu (n,c) and 64 Zn (n,p) was compared.

Dual control of cytosolic metals by lysosomal transporters in lobster hepatopancreas

This study describes the membrane transport mechanisms used by lobster (Homarus americanus) hepatopancreatic epithelial lysosomes to accumulate and sequester heavy metals from the cytosol, and thereby aid in the regulation of these ions entering the animal from dietary constituents. The present investigation extends previous work describing lysosomal metal uptake by cation exchange with protons and suggests that a second, parallel, lysosomal transport process involving metal-thiol conjugates may work in conjunction with the cation antiporter to control cytoplasmic metal concentrations. Transport of (65)Zn(2+) by lysosomal membrane vesicles (LMV) incubated in 1 mmol l(-1) glutathione (GSH) was not significantly different from metal transport in the absence of the tripeptide. However, preloading LMV with 1 mmol l(-1) alpha-ketoglutarate (AKG), and then incubating in a medium containing 1 mmol l(-1) GSH, more than doubled metal uptake, compared with vesicles equilibrated with chloride or possessing an outwardly directed chloride gradient. Kinetic analysis of lysosomal (65)Zn(2+) influx as a function of zinc concentration, in vesicles containing 1 mmol l(-1) AKG and incubated in 1 mmol l(-1) GSH, revealed the presence of a sigmoidal, low affinity, high capacity carrier process transporting the metal into the organelle. These data indicated the possible presence of an organic anion exchanger in lobster lysosomal membranes. Western blot analysis of LMV with a rabbit anti-rat OAT1 antibody showed the presence of an orthologous OAT1-like protein (approximate molecular mass of 80 kDa) signal from these membranes. These results, and those published previously, suggest the occurrence of two metal transporters on hepatopancreatic membranes, a high affinity, low capacity cation antiporter and a low affinity, high capacity organic anion exchanger. Together these two systems have the potential to regulate cytoplasmic metals over a wide concentration range.

Removal of radioactive caesium from low level radioactive waste (LLW) streams using cobalt ferrocyanide impregnated organic anion exchanger

The volumes of low level waste (LLW) generated during the operation of nuclear reactor are very high and require a concentration step before suitable matrix fixation. The volume reduction (concentration) is achieved either by co-precipitating technique or by the use of highly selective sorbents and ion exchange materials. The present study details the preparation of cobalt ferrocyanide impregnated into anion exchange resin and its evaluation with respect to removal of Cs in LLW streams both in column mode and batch mode operations. The Kd values of the prepared exchanger materials were found to be very good in actual reactor LLW solutions also. It was observed that the exchanger performed very well in the pH range of 3–9. A batch size of 6 g l −1 of the exchanger was enough to give satisfactory decontamination for Cs in actual reactor LLW streams. The lab scale and pilot plant scale performance of the exchanger material in both batch mode and column mode operations was very good.

Synthesis and characterization of cobalt ferrocyanides loaded on organic anion exchanger

Transition metal ferrocyanides have important applications in the selective removal of radioactive caesium from low level and intermediate level radioactive liquid waste streams. The microcrystalline nature of these materials renders them useless for application in column mode operations. Special preparation procedures have been developed to prepare granular solids by in situ precipitation of metal ferrocyanides on organic anion exchangers, which is suitable for column mode operations. The elemental compositions of the metal ferrocyanides precipitated inside the pores of anion exchanger were determined by analysing the dissolved samples using ICP–AES system and flame photometer. From the XRD and EDX analyses and the elemental composition of the synthesized materials, the nature of the compound formed inside the anion exchanger was found to be cobalt ferrocyanide. From SEM analysis of the samples, the particle size of the cobalt ferrocyanide precipitated inside the anion exchanger was found to be much less than that of cobalt ferrocyanide precipitated outside. The efficiency of these materials for removal of Cs was evaluated by measuring the distribution coefficient (Kd), ion exchange capacity and kinetics of Cs uptake. The Kd of the materials loaded on anion exchanger was found to be of the order of 10 5 ml/g. The Cs uptake kinetics of the materials loaded on anion exchanger was slower than that of precipitated materials. The ion exchange capacity of the cobalt ferrocyanide loaded on anion exchanger was found to be much higher than that of the precipitated cobalt ferrocyanide.

Stoichiometry of Removal of Natural Organic Matter by Ion Exchange

Five anion exchange resins, including a magnetic ion exchange (MIEX) resin, were evaluated for removal of Suwannee River Fulvic Acid (SRFA) in the presence of bicarbonate and chloride. The charge density of SRFA, obtained by potentiometric titration, was used to perform charge balances for ion exchange reactions involving SRFA, bicarbonate, and chloride under different solution conditions. The results clearly show the equivalence of SRFA uptake and chloride release by ion exchange. Although the structure of the anion exchange resins did not affect the stoichiometry of the reaction, the polyacrylic resins did exhibit greater removal of SRFA than the polystyrene resins. The hindered removal of SRFA by the polystyrene resins was hypothesized to be a result of size exclusion. The MIEX resin, which has a polyacrylic structure, performed similarly to the other polyacrylic resins. For the MIEX resin, the separation factor for SRFA over chloride was approximately 8 times greater than for bicarbonate over chloride. This work provides an improved understanding of the interactions between natural organic matter (NOM), inorganic anions, and anion exchange resins, and should result in more effective applications of ion exchange for the removal of NOM in the treatment of drinking water.

Involvement of organic anion transport system in transdermal absorption of flurbiprofen

We previously demonstrated that transdermal permeation of flurbiprofen is mediated by a nonlinear transport mechanism(s). Here, we aimed to characterize this transport mechanism by employing an Ussing-type chamber method with tape-stripped hairless mouse skin. Transdermal permeation of [ 3H]flurbipofen was vectorial, saturable and energy-dependent, suggesting the involvement of a carrier-mediated transport system. Transdermal permeation and uptake from the epidermal side of [ 3H]flurbiprofen were inhibited by various nonsteroidal anti-inflammatory drugs (NSAIDs). The inhibitory potency did not correlate well with lipophilicity; anionic NSAIDs tended to be more potent inhibitors than non-anionic NSAIDs. The inhibition profile of both [ 3H]flurbiprofen permeation and uptake, and the Michaelis constants, were similar for a given anionic compound. These results suggest that an organic anion transport system is involved in flurbiprofen uptake from the epidermal side during the process of transdermal absorption. Efflux of [ 3H]flurbiprofen from the skin to the epidermal side, but not to the hypodermal side, increased in the presence of flurbiprofen or several anionic compounds. Such trans-stimulation may suggest the involvement of an organic anion exchanger system. Organic anion transporter 2 (OAT2) is a candidate for the exchanger involved in uptake and/or efflux of flurbiprofen in the skin.

The Chloride Dependence of the Human Organic Anion Transporter 1 (hOAT1) Is Blunted by Mutation of a Single Amino Acid

Organic anion transporter 1 (OAT1) is key for the secretion of organic anions in renal proximal tubules. These organic anions comprise endogenous as well as exogenous compounds including frequently used drugs of various chemical structures. The molecular basis for the polyspecificity of OAT1 is not known. Here we mutated a conserved positively charged arginine residue (Arg(466)) in the 11(th) transmembrane helix of human OAT1. The replacement by the positively charged lysine (R466K) did not impair expression of hOAT1 at the plasma membrane of Xenopus laevis oocytes but decreased the transport of p-aminohippurate (PAH) considerably. Extracellular glutarate inhibited and intracellular glutarate trans-stimulated wild type and mutated OAT1, suggesting for the mutant R466K an unimpaired interaction with dicarboxylates. However, when Arg(466) was replaced by the negatively charged aspartate (R466D), glutarate no longer interacted with the mutant. PAH uptake by wild type hOAT1 was stimulated in the presence of chloride, whereas the R466K mutant was chloride-insensitive. Likewise, the uptake of labeled glutarate or ochratoxin A was chloride-dependent in the wild type but not in R466K. Kinetic experiments revealed that chloride did not alter the apparent K(m) for PAH but influenced V(max) in wild type OAT1-expressing oocytes. In R466K mutants the apparent K(m) for PAH was similar to that of the wild type, but V(max) was not changed by chloride removal. We conclude that Arg(466) influences the binding of glutarate, but not interaction with PAH, and interacts with chloride, which is a major determinant in substrate translocation.

Bifunctionalized mesoporous molecular sieve for perchlorate removal

Abstract Quaternary ammonium functionalized mesoporous media were synthesized for the effective removal of perchlorate. As a support host, mesoporous molecular sieve, SBA-15, was mono- or bifunctionalized with quaternary ammonium ions, N-((trimethoxysilyl)propyl)-N,N,N-trimethylammonium chloride (TSPMC) and N-((trimethoxysilyl)propyl)-N,N,N-tributylammonium chloride (TSPBC), by an incipient wetness impregnation method. Pore structures of the media were characterized by using nitrogen adsorption–desorption isotherms and an X-ray diffraction (XRD) analysis. The perchlorate adsorption speeds and capacities for the mono- or bifunctionalized SBA-15 were also examined, and compared with a conventional anion exchange resin (IRA-900). All the functionalized SBA-15 showed fast adsorption equilibriums within 10 min, while IRA-900 had a quite slow removal speed and did not reach an equilibrium for 5 h, as shown in other studies on a perchlorate removal with organic polymer anion exchange resins. The ammonium bifunctionalized mesoporous medium, 2 mmol of TSPMC and 2 mmol of TSPBC grafted into 1 g of SBA-15 (designated as MB22), showed a 1.14–1.39 (or 1.31–1.88) times higher adsorption capacity (or distribution coefficient) than those of monofunctionalized SBA-15. Compared to IRA-900, MB22 had about a 1400 times faster initial sorption rate. By considering the molecular size-selectivity, biodegradability, and thermal/chemical stability, quaternary ammonium bifunctionalized mesoporous molecular sieves are thought to have lots of merits for a perchlorate-containing water treatment.

Functional characterization of human organic anion transporter 4 (hOAT4) in a Baculovirus expression system

In the renal proximal tubule, organic anion transporters (OATs) mediate the removal of endogenous and exogenous toxins from blood for excretion in urine. OATs at the basolateral membrane drive organic anions into the cells, through exchange for dicarboxylates. At the apical membrane, different transporters deliver organic anions to the lumen. hOAT4 resides in the apical membrane, but its role in transport is unclear. Here we describe a new expression system to characterize hOAT4 and other OATs. An insect cell line (Sf9) was infected with Baculovirus containing hOAT4 cDNA under the control of the polyhedrin promoter. Although ABC transporters have been expressed using Baculovirus, this is the first report of insect cell expression of any OAT. Membrane vesicles from infected Sf9 cells transported known hOAT4 substrates (DHEAs, MTX and OTA) in a time-dependent manner. hOAT4-specific accumulation was inhibited by probenecid and increased when vesicles were preloaded with glutarate, suggesting organic anion exchange. In summary, Baculovirus-expressed hOAT4 is functionally consistent with protein from other systems. Isolated membrane vesicles derived from Baculovirus-infected Sf9 cells can therefore be used to characterize the mechanisms by which OATs function. This research was supported by the Intramural Research Program of the NIH, NIEHS.

Functional Role of the C Terminus of Human Organic Anion Transporter hOAT1

Functional Role of the C Terminus of Human Organic Anion Transporter hOAT1

Exchange characteristics of monocarboxylic acids and monosulfonic acids onto anion-exchange resins

In the previous paper (N. Kanazawa, K. Urano, N. Kokado, Y. Urushigawa, J. Colloid Interface Sci. 238 (2001) 196), the equilibria of propionic acid and benzoic acid adsorption onto three anion-exchange resins were investigated, and an equation was proposed that summed of the physical adsorption of the carboxylic acid molecule and the ion exchange of the dissociated carboxylate ion. The ion exchange equation, including a selectivity coefficient to chloride ion for each combination between carboxylate ions and anion-exchange resins, could be used in wide ranges of concentration and pH. In this research, ion-exchange equilibria using 16 anion-exchange resins and 9 organic acids including monocarboxylic and monosulfonic acids were investigated. It could be confirmed that the proposed equation applied to the ion exchange with these monoorganic acids. Characteristics of ion exchange between the organic anions and anion exchange were also studied by the selectivity coefficients.

Uric acid transport.

The goal of this article is to review the physiology and describe newly defined molecular mechanisms that are responsible for renal urate transport. Four complementary DNAs have recently been cloned whose expressed proteins transport urate. Two of these proteins have been localized to the apical membrane of proximal tubular cells: one, a urate transporter/channel, a galectin, is an electrogenic transporter (an ion channel); the second is a urate-anion electroneutral exchanger, a member of the organic anion transporter family. The other urate transport proteins, organic anion transporters 1 and 3, are also members of the organic anion transporter family. These proteins have been localized to the basolateral membrane of proximal tubular cells: organic anion transporter 1 is an electroneutral organic anion exchanger; the mechanism of urate transport on organic anion transporter 3 remains to be determined. The molecular definition and localization of four urate transport proteins provides a basis for developing a molecular model of the bi-directional transport of urate in renal proximal tubules. It seems likely that the urate-anion exchanger is responsible for luminal reabsorption while the urate transporter/channel permits secretion of urate from the cell into the lumen. Since organic anion transporters 1 and 3 reside in the basolateral membrane, one or both may be relevant in the reabsorptive flux of urate into the peritubular capillary as well as in the cellular uptake of urate from the peritubular space, the first step in the process of urate secretion. Knowledge of the molecular basis of urate transport should provide greater insights into states of altered transport as well as assist in development of drugs to modify urate flux.

Relationships between biological and physico-chemical soil characteristics in a mediterranean agricultural area

Fourteen agricultural soils from various areas of Tuscany were characterized by a range of measurements indicative of soil biological activity. The objective of our research was to identify soil parameters suitable as indicators for evaluating their quality. In general, enzyme activities were found to vary widely, with the highest activity for each enzyme being distributed among only five of the 14 soils studied. The narrowest range (14-fold) in enzyme activities for the various soils was observed for catalase and the widest range (577-fold) for g -glucosidase. Biomass C and, among the measured enzyme activities, amylase, were well correlated with total organic carbon, total N, cation and anion exchange capacity. Positive correlations were found between the maximum water holding capacity and dehydrogenase, amylase, biomass C, FDA hydrolytic activity, the biological index of fertility and the enzyme activity number, so showing that soil moisture may play an important role in affecting soil biological characteristics. No significant correlations were observed among the soil enzymes themselves. The FDA hydrolytic activity appeared to be the index most related with the other biological characteristics tested in this study and, for this reason, can be considered the most effective index for putting in evidence relationships existing between the different biological characteristics in the soils investigated.

SORPTION OF TUNGSTEN(VI) AND RHENIUM(VII) ON VARIOUS ION-EXCHANGE MATERIALS

The comparative distribution coefficients of W and Re on Al2O3, H-ZrO2, Silica-gel, Charcoal, HAP, Lead, H-MnO2, H-CeO2, H-TiO2, H-SnO2, organic anion, and cation exchangers were determined at different pH values and acid concentrations, in order to choose the most suitable exchanger for construction of a188W → 188Re generator. The experimental results clearly select Al2O3 as the best adsorbent. Other adsorbents may find application as tandem a column matrix to reduce the 188W breakthrough in the final 188ReO− 4 eluate.

Human platelets express gangliosides with LKEactivity and ABH blood group activity

Platelets express several neutral glycosphingolipids with ABH and P blood group activity that may play a role in infectious, autoimmune, and alloimmune thrombocytopenia. In RBCs, sialylated glycosphingolipids or gangliosides with blood group activity have also been reported. To determine whether similar antigens are expressed by platelets, the total platelet ganglioside fraction was isolated and screened for blood-group-active glycosphingolipids. Platelet gangliosides were isolated by organic extraction, base hydrolysis, anion exchange, silicic acid, and high-performance liquid chromatography. Gangliosides were identified and characterized by high-performance thin-layer chromatography-immunostaining with blood group-specific MoAbs and glycosidase digestion. Group A, but not group O, platelets express five gangliosides with group A activity. Of five A MoAbs and lectins examined, only MoAbs Birma-1 and MHO4 recognized all five sialyl A bands. The sialyl A bands were sensitive to endoglycoceramidase and neuraminidase. One sialyl A band may represent a branched ganglioside with sialyl-I and group A activity. Platelets also express an LKE-active ganglioside consistent with sialyl-galactosylgloboside. In addition to sialyl-iI and sialyl-Le(x) gangliosides, group A platelets express gangliosides with LKE activity and group A activity. Like RBCs, group A-active gangliosides may act as alloantigens and autoantigens to naturally occurring isohemagglutinins.

Drug secretion systems in renal tubular cells: functional models and molecular identity.

For the last several decades, functional characterization of renal drug handling has provided the conceptual framework of drug transport, especially drug secretion by the renal tubular cells. Functional models have been postulated for the two distinct groups of drugs with regard to their ionization characteristics at physiological pH (i.e., organic cations and organic anions). Organic cations are predicted to cross the basolateral membranes through a potential-sensitive uptake system along an inside-negative potential gradient, with secretion of organic cations into urine across apical membranes appearing to occur via a proton-organic cation antiport system. Organic anions are predicted to enter the cells against an electrical-potential gradient through basal membranes via an organic anion-dicarboxylic acid exchanger. Secretion of organic anions into urine across apical membranes is less well characterized, but the presence of an organic anion exchanger and a potential-driven transporter is hypothesized. Recent data obtained using molecular biology techniques have helped to elucidate molecular identity of each system postulated in these models. Novel drug transport proteins have also been discovered that were not part of the original organic cation/anion model, such as P-glycoprotein for hydrophobic neutral and cationic compounds. Moreover, the search for homologous genes of these transporters has led to the discovery of previously unknown transporter proteins, whose function has yet to be identified. Integral roles of these transport proteins in overall tubular handling of drugs remain to be determined.