Weak Ion Exchange Research Articles

Removal of cobalt, strontium and cesium from radioactive laundry wastewater by ammonium molybdophosphate–polyacrylonitrile (AMP–PAN)

Applicability of ammonium molybdophosphate–polyacrylonitrile (AMP–PAN) on the adsorptive removal of Co, Sr and Cs in the radioactive laundry wastewater generated from nuclear power plants was investigated. Single- and bi-solute competitive adsorptions of Co 2+, Sr 2+ and Cs + onto AMP–PAN were investigated. The influencing factors such as co-existing metal ion and surfactants were investigated. Adsorption of Co 2+, Sr 2+ and Cs + onto AMP–PAN occurs via both physical adsorption due to weak van der Waals forces and ion exchange of ammonium molybdophosphate. The results of adsorption model analyses showed that AMP–PAN has high selectivity for Cs +. The maximum adsorption capacities were 0.16, 0.18 and 0.61 mmol/g for Co 2+, Sr 2+ and Cs +, respectively. In bi-solute competitive adsorptions, adsorption of one metal ion was suppressed by the presence of competing metal ion. Alkali metal (Na +) inhibits adsorption of Cs + and the presence of Ca 2+ ion decreased the adsorption of Co 2+ onto AMP–PAN. Adsorption behaviors of Co 2+, Sr 2+ and Cs + onto AMP–PAN in the presence of surfactants were quiet different. The presence of cationic (OTMA and HDTMA) and anionic surfactants (SDBS and SOBS) decreased adsorption of Co 2+, Sr 2+ and Cs + onto AMP–PAN, but that of non-ionic surfactants (Tween 80 and Triton X-100) did not.

A novel solid phase extraction method for pre-concentration of gadolinium and gadolinium based MRI contrast agents from the environment

An efficient solid phase extraction (SPE) method using bis-(2-ethylhexyl)-phosphate (HDEHP) coated reverse phase C18 support has been developed for the pre-concentration of Gadolinium (Gd) and Gd contrast agents widely used in magnetic resonance imaging (MRI). Enrichment of Gd in the ionic form has been compared with strong cation exchange material Chromabond SA (SCX), weak ion exchange material Chelex-100 and also with lanthanide specific HDEHP modified reverse phase C18. The determination of Gd and its complexes after enrichment were performed using inductively coupled plasma mass spectrometry (ICP-MS) and on the basis of 158Gd. Among the three SPE materials, HDEHP coated reverse phase C18 SPE has been found to be most efficient, yielding a hundredfold Gd enrichment with > 95% recovery for linear and cyclic contrast agents like Gd-DTPA (Magnevist), Gd-DOTA (Dotarem), Gd-BOPTA (Multihance), and Gd-BT-DO3A (Gadovist). The developed SPE method has been successfully applied to the surface water and waste water samples originated from different places in Berlin, Germany. The results were in good agreement with the results obtained with direct measurement with ICP-MS. The developed pre-concentration method can be efficiently used for the determination of trace levels of gadolinium in the environment even with less sensitive analytical techniques.

Silver sorption on acrylic copolymers functionalized with amines. Equilibrium and kinetic studies

Abstract The sorption capacity of three weak base ion exchangers based on acrylic copolymers functionalized with ethylenediamine, triethylenetetramine and N, N- dimethylamino propylamine for Ag(I) ions was evaluated. Adsorption experiments were carried out by batch method. The effect of pH, crosslinking degree of copolymers, amount of sorbent, initial ion concentration, contact time and temperature was studied. The parameters which characterize the retention process were estimated using Langmuir and Freundlich isotherm models, the best fitting being for the first model. Kinetic data were fitted to pseudo-first order, pseudo-second order and intraparticle diffusion models. Experimental data were in good agreement with the pseudo second order.

The cleaning of burned and contaminated archaeological maize prior to 87Sr/ 86Sr analysis

Accurate trace-metal and strontium-isotope analyses of archaeological corn cobs require that metal contaminants be removed prior to chemical analysis. Archaeological cobs are often coated with construction debris, dust, or soil which contains mineral particles. In addition, most archaeological cobs are partially or completely burned and the burned parts incorporate mineral debris in their hardened residual structures. Unburned cobs are weak ion exchangers and most metals within a cob are not firmly bound to cob organic matter; therefore, immersing cobs in acids and rinsing them in deionized water to remove mineral contaminants may result in the undesirable loss of metals, including strontium, from the cob. In this paper we show that some cob metal-pair ratios are not substantially changed when the cob is “cleaned” with deionized water, if the water-cob contact time does not exceed five minutes. Additionally, we introduce a method for eliminating mineral contaminants in both burned and unburned cobs, thus rendering them acceptable for strontium-isotope analysis. However, the decontamination procedure results in the rapid non-stoichiometric leaching of trace metals from the unburned cobs and it is possible that most metals will be extracted from the cobs during the lengthy decontamination process. Trace metals, in particular Al and Ca, should be analyzed in order to determine the presence and level of mineral contamination after cleaning.

Characterization of monoclonal antibodies using polymeric cation exchange monoliths in combination with salt and pH gradients

The characterization of three different mAb formulations of pharmaceutical interest is demonstrated using cation exchange polymethacrylate-based monolithic columns as well as imaged CE (iCE). Elution of the mAbs from both a strong cation exchanger (ProSwift SCX-1S) and a weak cation exchanger (ProSwift WCX-1S) was readily achieved employing a linear salt gradient or a mixed buffer pH gradient indicating that either approach can be used in purification or isolation. Using a linear salt gradient, the elution profile on the two types of exchangers was found to differ indicating that the combination of both strong and weak ion exchangers is needed for complete characterization. The elution profile of two of the mAbs on the strong cation exchanger used in combination with a linear pH gradient from pH 4 to 10 showed signs of charge heterogeneity. The use of iCE was found to be the best choice for characterization of charge heterogeneity, showing a clear charge distribution for all three mAbs.

1 mm ID poly(styrene‐co‐divinylbenzene) monolithic columns for high‐peak capacity one‐ and two‐dimensional liquid chromatographic separations of intact proteins

The LC performance of a 1x50 mm polymer monolithic column format was demonstrated with high-peak capacity one- (1D) and offline two dimensional (2D) LC separations of intact proteins. After optimizing the RP 1D-LC conditions, including column temperature, flow rate and gradient time, a peak capacity of 475 was achieved within a 2-h analysis. The suitability of the monolithic column was also demonstrated for fast 1 min protein separations yielding 1 s peak widths determined at half peak height. In addition, an offline 2D-LC method was developed using the micro-fraction collection capabilities of the autosampler allowing automatic fractionation of intact proteins after the weak-ion-exchange (WAX) separation, and re-injection of the fractions onto the second-dimension RP monolithic column. The best peak capacity-to-analysis time ratio was obtained when applying 10 min second-dimension RP gradients. At optimized conditions, the WAX/x/RPLC separation of intact Escherichia coli proteins was performed within 6 h yielding a maximum theoretical peak capacity of 4880.

Extraction and Determination of Cefazolin Sodium and Cefotaxime Sodium in Human Urine with a Weak Ion Exchange Monolithic Column

An online solid phase extraction (SPE) method was developed for the simultaneous screening of cefazolin sodium and cefotaxime sodium in human urine. A short weak anion exchange monolithic column was prepared and used as the selective extraction sorbent. The column exhibited good permeability and biocompatibility. During the online SPE process, most matrices in the urine samples were removed rapidly, while cefazolin sodium and cefotaxime sodium were effectively trapped in this monolithic column. Reversed phase high performance liquid chromatography (HPLC) was performed on a C18 column with ultraviolet detection at 254 nm. The mobile phase consisted of methanol-0.005 mol/L phosphate (21/79, v/v, pH = 5.0) and the flow rate was set to 0.7 mL/min. A good linear relationship was demonstrated at analyte concentrations ranging from 1 to 100 µg/mL. The absolute recovery ranged from 79.4% to 81.5% and the inter- and intra-day relative standard deviations were <5.0%. These results suggest that the online SPE-HPLC method is suitable for the simultaneous monitoring of cefazolin sodium and cefotaxime sodium in human urine samples because it avoids tedious pretreatments and provides a fast, economical, and reproducible method for assaying trace drugs in biological samples.

Proteomics analysis of liver pathological calcification suggests a role for the IQ motif containing GTPase activating protein 1 in myofibroblast function.

To date the cellular and molecular mechanisms by which liver pathological calcifications occur and are regulated are poorly investigated. To study the mechanisms linked to their appearance, we performed a proteomics analysis of calcified liver samples. To this end, human liver biopsies collected in noncalcified (N), precalcified (P), and calcified (C) areas of the liver were subjected to weak ion exchange chromatography, SDS-PAGE, and LC-ESI MS/MS analyses. As we previously demonstrated that alpha-smooth muscle actin (α-SMA) expressing myofibroblasts were involved in liver pathological calcification, we performed a targeted analysis of actin cytoskeleton remodeling-related proteins. This revealed dramatic changes in protein expression patterns in the periphery of the calcified areas. More particularly, we found that IQGAP1 and IQGAP2 proteins were subjected to major expression changes. We show that IQGAP1 expression within P and C areas of the liver correlates with the high abundance of myofibroblasts and that IQGAP1 is specifically expressed in these cells. In addition, we find that IQGAP1 is part of a protein complex including β-catenin and Rac1 mainly in P and C regions of the liver. These results suggest that IQGAP1 may play a critical role in the regulation of cytoskeleton remodeling in liver myofibroblasts in response to liver injury and consequently impact on their function.

High‐Throughput Process Development: Determination of Dynamic Binding Capacity Using Microtiter Filter Plates Filled with Chromatography Resin

Steadily increasing demand for more efficient and more affordable biomolecule-based therapies put a significant burden on biopharma companies to reduce the cost of R&D activities associated with introduction of a new drug to the market. Reducing the time required to develop a purification process would be one option to address the high cost issue. The reduction in time can be accomplished if more efficient methods/tools are available for process development work, including high-throughput techniques. This paper addresses the transitions from traditional column-based process development to a modern high-throughput approach utilizing microtiter filter plates filled with a well-defined volume of chromatography resin. The approach is based on implementing the well-known batch uptake principle into microtiter plate geometry. Two variants of the proposed approach, allowing for either qualitative or quantitative estimation of dynamic binding capacity as a function of residence time, are described. Examples of quantitative estimation of dynamic binding capacities of human polyclonal IgG on MabSelect SuRe and of qualitative estimation of dynamic binding capacity of amyloglucosidase on a prototype of Capto DEAE weak ion exchanger are given. The proposed high-throughput method for determination of dynamic binding capacity significantly reduces time and sample consumption as compared to a traditional method utilizing packed chromatography columns without sacrificing the accuracy of data obtained.

Identification of trimeric peptides that bind porcine parvovirus from mixtures containing human blood plasma.

Virus contamination in human therapeutics is of growing concern as more therapeutic products from animal or human sources come into the market. All biopharmaceutical processes are required to have at least two distinct viral clearance steps to remove viruses. Most of these steps work well for enveloped viruses and large viruses, whether enveloped or not. That leaves a class of small non‐enveloped viruses, like parvoviruses and hepatitis A, which are not easily removed by these typical steps. In this study, we report the identification of trimeric peptides that bind specifically to porcine parvovirus (PPV) and their potential use to remove this virus from process solutions. All of the trimeric peptides isolated completely removed all detectable PPV from buffer in the first nine column volumes, corresponding to a clearance of 4.5–5.5 log of infectious virus. When the virus was spiked into a more complex matrix consisting of 7.5% human blood plasma, one of the trimers, WRW, was able to remove all detectable PPV in the first three column volumes, after which human blood plasma began to interfere with the binding of the virus to the peptide resin. These trimer resins removed considerably more virus than weak ion exchange resins. The results of this work indicate that small peptide ligand resins have the potential to be used in virus removal processes where removal of contaminating virus is necessary to ensure product safety.

Determination of immobilized enzyme apparent kinetic parameters in packed-bed reactors: Presentation of a new methodology

A new explicit equation is proposed for the determination of immobilized enzyme apparent Michaelis–Menten kinetic parameters in packed-bed reactors. The mathematical analysis is based on recycling systems. The present methodology is easily applicable for a wide range of operating conditions. It is free from the probable limitations of the single-pass apparent immobilized enzyme kinetic parameter estimation technique that requires simultaneous measurement of column substrate inlet and effluent concentrations at a specified time. The experimental system is composed of a substrate reservoir and a circulating flow packed-bed immobilized enzyme reactor. The experimental data is gathered for glucose decomposition reaction in a recirculation system with immobilized glucose oxidase on a weak base ion exchanger resin. The apparent kinetic parameter, K ′ m values were calculated with a new explicit equation, proposed in this work, and they are found to be 0.48 × 10 −3 and 0.60 × 10 −3 mmol cm −3 for the recirculation rates of 75 and 25 cm 3 min −1, respectively.

Kinetics Characterization of Ion Release under Dynamic and Batch Conditions. I. Weak Acid and Weak Base Ion Exchange Resins

The aim of the present work is concerned with a study of the kinetics of release of both Ca2+ and F− from the corresponding loaded ion-exchange resins (weak acid and weak base character for Ca2+ for F−, respectively), using both dynamic and batch experimental conditions with an artificial saliva solution as the ion-exchange media at 293 and 310 K. The influence of resin particle size and the temperature were evaluated by the kinetics parameters for the effective rate of release (B) and diffusion coefficient (D). The rate of ion release increases with temperature and decreases with particle size. The experimental data were well fitted by models based on intraparticle diffusion-controlled processes. In dynamic studies, the linear dependence of −log 10(B) with the diameter of the resin particles can be applied for the estimation of B values when resins of low particle size are considered. In batch processes, although resins of low particle size can be studied, a linear relationship was only attained for the case of slow ion-exchange kinetic systems.

New technology for heavy oil exploitation wastewater reused as boiler feedwater

Abstract Steam Assisted Gravity Drainage (SAGD) or non-SAGD heavy oil recovery process uses a considerable amount high-pressure steam and produces significant amount of oily wastewater. Conventional water treatment and steam generation process is very complex, producing poor quality water for reuse and low energy efficiency. Using evaporation process to replace those conventional treatment processes first emerged in Albert, North America. This eventually resulted in introducing conventional drum boiler to replace once-through steam generator to produce steam. The paper introduces evaporation technology to treat heavy oil wastewater and produce high-quality boiler feed water. It also provides comparison data between evaporation and conventional process (warm lime softening and weak acid cation ion exchange) from technical and operational aspects. Conclusion is that evaporation provides an alternate approach to produced water treatment, which is simpler, more cost effective and more reliable, and reduces complexity of the steam generation system. Additional steps can be taken to recover all liquid waste streams for reuse in the plant, resulting in zero liquid discharge.

Characterization of ion exchange stationary phases via pH transition profiles

New non-destructive method for characterization of ion exchange chromatographic columns based on transient pH formed by a step change in ionic strength of buffer solutions was examined. The method was used to distinguish between cation and anion or weak and strong ion exchange chromatographic supports and to determine the capacity of the chromatographic resins. The general scheme to distinguish between most commonly used types of ion exchange chromatographic columns was proposed. The duration of pH transient was shown to be linearly proportional to the total ionic capacity and was used to estimate protein dynamic binding capacity of the resin. The effects of pH, concentration and temperature on transient pH duration were examined.

On-line clean-up and screening of oxacillin and cloxacillin in human urine and plasma with a weak ion exchange monolithic column

A weak ion exchange monolithic column prepared by modifying the GMA–MAA–EDMA (glycidyl methacrylate–methacrylic acid–ethylene glycol dimethacrylate) monoliths with ethylenediamine was applied to remove matrix compounds in biological fluid. Using this monolithic column, on-line clean-up and screening of oxacillin and cloxacillin in human urine and plasma samples had been investigated. Chromatography was performed by reversed-phase HPLC on a C 18 column with ultraviolet detection at 225 nm. Results showed that the ion exchange monolithic column could be used for deproteinization and retaining oxacillin and cloxacillin in human urine and plasma, which provided a simple and fast method for assaying drugs in human urine and plasma.

A Tentative Explanation for the Substantial Rise of the Gelatinization Temperature of Starch by Adding Salt and Hydroxide

The effects of three saline solutions, LiCl, NaCl, and KCl, on the gelatinization temperature of starch-salt systems were studied. The same but systems with the addition of NaOH were also studied. A rise of gelatinization temperature of all starch-salt-water systems studied was observed. The gelatinization range (ΔTgr) of starch-salt-water systems, was not affected by the nature of the cation; instead it was affected by its concentration; the rise of the gelatinization temperature (ΔTgel) and gelatinization enthalpy (ΔH) were not affected by the nature and concentration of the cation. The rise of the gelatinization temperature (ΔTgel) of starch-salt-NaOH-water systems was significantly affected by the nature and concentration of the cation, and by the concentration of NaOH. Li+ was responsible for a smaller rise of gelatinization temperature and K+ for a greater rise of gelatinization temperature. Increases in the gelatinization temperature of up to 48.0°C were measured. These results may indicate that the rise in gelatinization temperature of starch-salt-NaOH-water systems could be explained based on the assumption that starch behaves as a weak ion exchanger governed by the Donnan potential.

Adsorption of Lactic Acid on Weak Base Polymeric Resins

Sorption of lactic acid from a simulated broth has been investigated using weak base ion exchange polymeric resins which behave as functionalized polymers because of tertiary amino groups on the polymer matrix. The equilibrium data for the uptake of lactic acid are represented by Langmuir‐Freundlich combination isotherm. The sorption has been modeled by a phase equilibrium approach using the extended Flory‐Huggins theory of polymer solutions. The interaction of media components, such as glucose and inorganic salts, with the resins and their effect on lactic acid sorption, also has been investigated.

Monodisperse porous polymer particles with polyionic ligands for ion exchange separation of proteins

A new “grafting to” strategy was proposed for the preparation of polymer based ion exchange supports carrying polymeric ligands in the form of weak or strong ion exchangers. Monodisperse porous poly(glycidyl methacrylate-co-ethylene dimethacrylate), poly(GMA-co-EDM) particles 5.9 μm in size were synthesized by “modified seeded polymerization”. Poly(2,3-dihydroxypropyl methacrylate-co-ethylene dimethacrylate), poly(DHPM-co-EDM) particles were then obtained by the acidic hydrolysis of poly(GMA-co-EDM) particles. The hydroxyl functionalized beads were treated with 3-(trimethoxysilyl)propyl methacrylate to have covalently linked methacrylate groups on the particle surface. The selected monomers carrying weak or strong ionizable groups (2-acrylamido-2-methyl-1-propane sulfonic acid, AMPS; 2-dimethylaminoethylmethacrylate, DMAEM and N-[3-(dimethylamino)propyl] methacrylamide, DMAPM) were subsequently grafted onto the particles via immobilized methacrylate groups. The final polymer based materials with polyionic ligands were tried as chromatographic packing in the separation of proteins by ion exchange chromatography. The proteins were successfully separated both in the anion and cation exchange mode with higher column yields with respect to the previously proposed materials. The plate heights obtained for poly(AMPS) and poly(DMAEM) grafted poly(DHPM-co-EDM) particles by using proteins as the analytes were 80 and 200 μm, respectively. Additionally, the plate height exhibited no significant increase with the increasing linear flow rate in the range of 1–20 cm/min. The most important property of the proposed strategy is to be applicable for the synthesis of any type of ion exchanger both in the strong and weak form.

Surface charge on loose nanofiltration membranes

The main objective of this work was to study the effect of salt concentration and pH on the surface charge of loose nanofiltration (NF) membranes through streaming potential measurements. A Dow pilot unit equipped with a plate-and-frame module allowed the simultaneous test of two commercial NF membranes: Celgard N30F and Celgard NF-PES-10. Permeation of 0.2–18 mol/m3 NaCl solutions was carried out at constant flow rate and ambient temperature, 2.5–12.5 bar, whereas pH ranged from 5 to 7. The ion exchange capacity (IEC) of the membranes was assessed by potentiometric titration. The streaming potential developed in NaCl solutions (0.2–5 mol/m3; pH = 5–7) flowing along a thin rectangular slit formed by two parallel identical membranes was measured by an EKA electrokinetic analyser, which automatically calculated the zeta potential through the Helmholtz-Smoluchowsky equation and corrected it for the membrane surface conductance. The membrane surface charge was determined through the Gouy–Chapmann equation. Both membranes bear low negative charge densities, the absolute magnitude of which decreased for decreasing pH, as the membrane isoelectric point was approached. The absolute magnitude of the membrane surface charge increased for increasing concentrations, due to the progressive adsorption of anions onto the membrane surface, though it was impossible to glimmer a Freundlich adsorption isotherm, due to the scattering of streaming potential data at concentrations above 5 mol/m3. The ion exchange capacities of the membranes permselective layers were in the range of weak ion exchange membranes. However, IEC data were one order of magnitude higher than the maximum charge densities assessed by electrokinetic measurements.

Binding kinetics of magnetic nanoparticles on latex beads and yeast cells studied by magnetorelaxometry

The ion exchange mediated binding of magnetic nanoparticles (MNP) to modified latex spheres and yeast cells was quantified using magnetorelaxometry. By fitting subsequently recorded relaxation curves, the kinetics of the binding reactions was extracted. The signal of MNP with weak ion exchanger groups bound to latex and yeast cells scales linearly with the concentration of latex beads or yeast cells whereas that of MNP with strong ion exchanger groups is proportional to the square root of concentration. The binding of the latter leads to a much stronger aggregation of yeast cells than the former MNP.