Novel synthesis of natural cation exchange resin by crosslinking the sodium alginate as a natural polymer with 1,6-hexamethylene diisocyanate in inert solvents: Characteristics and applications.

Novel synthesis of natural polymeric cation exchanger from sodium alginate reagent as natural polymer (CAlg-Na)n has been developed. This procedure takes place by crosslinking the solid sodium alginate with 1,6-hexamethylene diisocyanate (HDI) in dryness benzene as inert solvent (DB). The experimental results for crosslinking the alginate using different degrees of crosslinking of HDI/DB (w/w) showed that the capacity of the synthesized resin for binding the polyvalent metal ions reached its maximum at 30% of (HDI/D) ratio. This work aims to present a novel synthesis of cation exchange resin from natural polymers as an alternative promising competitor of low-cost, high performance and non-toxicity for removal of the toxic heavy metal ions in wastewater remediation and radionuclide pollutants from environmental contaminated media. The results obtained from various applied techniques for determining the bounded metal ion concentrations with (CAlg-Na)n indicated that the resin capacity was followed the order U(VI) > Cu(II) > Sr(II) > Ca(II) at 25 °C, respectively. The factors influenced the alginate affinity for chelating the metal ions were explained in some correlation terms between the alginate capacity and some physicochemical properties of chelated metal ions and its respective formed complexes. Speculated geometrical configurations for chelation were suggested and discussed.

Strong cation exchange monoliths for HPLC by Reactive Gelation.

Polymeric monolithic stationary phases for HPLC can be produced by Reactive Gelation. Unlike the conventional method of using porogens, such novel process consists of a number of separate steps, thus enabling a better control of the quality of the final material. A suspension of polymer nanoparticles in water is produced and subsequently swollen with hydrophobic monomers. The particles are then destabilised (usually by salt addition) to make them aggregate into a large percolating structure, the so-called monolith. Finally, the added monomer can then be polymerised to harden the structure. In this work, a polystyrene latex is used as the base material and functionalised by introduction of epoxide groups on the surface and subsequent reaction to sulphonic acid groups, yielding a SO3(-) density of 0.7 mmol/g dry material. Morphological investigations show 54% porosity made of 300 nm large pores. Van Deemter measurements of a large protein show no practical influence of diffusion limitations on the plate number. Finally, a preliminary separation of a test protein mixture is shown, demonstrating the potential of using ion-exchange chromatography on Reactive Gelation monoliths.

Synthesis and characterization of nano-composite ion-exchanger; its adsorption behavior.

A novel organic-inorganic nanocomposite cation-exchanger has been synthesized via sol-gel method. It was characterized on the basis of FTIR, XRD, SEM, TEM, AFM and Raman studies. The structural studies reveal semi-crystalline nature of the material with the particle size ranging from 1-5 nm. Physiochemical properties such as ion-exchange capacity, chemical and thermal stability of composite material have also been determined. Bifunctional behavior of the material has been indicated by its pH titrations curves. The nanocomposite material exhibits improved thermal stability, higher ion-exchange capacity and better selectivity for toxic heavy metals. The ion-exchange material shows an ion-exchange capacity of 1.8 meq g(-1) for Na(+) ions. Sorption behavior of metal ions on the material was studied in different solvents. The cation exchanger was found to be selective for Pb(II), Hg(II) and Zr(IV) ions. The limit of detection (LOD) and the limit of quantification (LOQ) for Pb(II) ion was found to be 0.85 and 2.85 µg L(-1). Analytically important separations of heavy metal ions in synthetic mixtures as well as industrial effluents and natural water were achieved with the exchanger. The practical utility of polyanilineZr(IV)sulphosalicylate cation exchanger has been established for the analysis and recovery of heavy metal ions in environmental samples.

Immobilization of polyethylenimine nanoclusters onto a cation exchange resin through self-crosslinking for selective Cu(II) removal.

Donnan membrane principle provides great opportunities for development of highly efficient adsorbents for toxic metals abatement. Based on the principle we prepared a new composite adsorbent by immobilizing polyethylenimine (PEI) nanoclusters within a macroporous cation exchanger D001 through self-crosslinking by glutaraldehyde upon Cu(II)-template process. Negligible PEI loss was observed from the resultant composite adsorbent D001-PEI-GA to solution of pHs 1-12. Increasing solution pH from 1 to 6 results in more favorable Cu(II) retention by D001-PEI-GA, and Cu(II) adsorption onto D001-PEI-GA follows the pseudo-second-order kinetic model well. Compared to D001, D001-PEI-GA displays more preferable Cu(II) sequestration in the presence of co-ions Mg(2+), Ca(2+), Sr(2+) at higher levels. Fixed-bed adsorption of a synthetic solution containing Cu(II) and other co-ions showed that Cu(II) sequestration on D001-PEI-GA could result in its conspicuous decrease from 5mg/L to below 0.01 mg/L with the treatment volume as high as 630 BV per run, while that for D001 was only ∼ 85 BV. Also, the spent composite adsorbent can be readily regenerated by HCl (0.3M)-NaCl (0.5M) binary solution for repeated use with negligible capacity loss.

Preparation and characterization of chitosan-grafted-poly(2-amino-4,5-pentamethylene-thiophene-3-carboxylic acid N'-acryloyl-hydrazide) chelating resin for removal of Cu(II), Co(II) and Ni(II) metal ions from aqueous solutions.

The graft copolymerization of ethylacrylate (EA) onto chitosan initiated by potassium persulphate and Mohr's salt combined redox initiator system in limited aqueous medium was carried out in heterogeneous media. Moreover, modification of the grafted chitosan was carried out by reaction of the ester group (-COOEt) with 2-amino-4,5-pentamethylene-thiophene-3-carboxylic acid hydrazide which eventually produce chitosan-grafted-poly(2-amino-4,5-pentamethylene-thiophene-3-carboxylic acid N'-acryloyl-hydrazide) (chitosan-g-ATAH) chelating resin. The application of the modified resin for metal ion uptake was studied using Cu(2+), Co(2+) and Ni(2+) ions. The modified chelating resins were characterized using FTIR spectroscopy, SEM and X-ray diffraction.

Weak cation-exchange monolithic column for capillary liquid chromatography of peptides and proteins.

A stable poly(2-carboxyethyl acrylate-co-poly(ethylene glycol) diacrylate) monolith was synthesized inside a 75-µm id capillary by direct in situ photo-initiated polymerization in a binary porogenic solvent consisting of methanol and ethyl ether. The resulting monolith was evaluated for weak cation-exchange capillary liquid chromatography of peptides and proteins. A high dynamic binding capacity of 72.7 mg lysozyme per cm3 column volume was measured. Fast mass transfer was demonstrated by steep breakthrough curves. The resulting monolith exhibited negligible hydrophobicity, leading to good separation of peptides and proteins. Peak capacities of 11 for peptides with a 10-min salt gradient and 39 for proteins with a 20-min salt gradient were measured. An efficiency of 37,000 plates/m for proteins was obtained under isocratic conditions. The effects of functional group concentration, porogenic solvent composition, mobile phase pH, salt gradient rate, and hydrophobicity on the retention of analytes were investigated. Good run-to-run relative standard deviation (RSD) <1.93% and column-to-column RSD <4.63% were achieved.

[Preparation of strong cation-exchange monolithic column and its application in polypeptide separation by capillary electrochromatography].

A strong cation-exchange monolithic column was prepared by polymerization inside the fused-silica capillary. The solution consisted of acrylic acid and 2-acrylamido-2-methyl-1-propanesulfonic acid as functional monomers, N,N'-methylenebisacrylamide as a cross-linking agent, dimethyl suiphoxide and dodecanol, 1 , 4-butanediol as organic porogenic solvents and azobisisobutyronitrile as a suitable initiator. The effects of the applied voltage, concentrations of organic modifier and salt solution, pH value on the electroosmotic flow were investigated. The experimental results showed that there existed a good linear relationship between the applied voltage and electroosmotic flow with a correlation coefficient of 0.9981; When the concentration of organic modifier (acetonitrile, ACN) was less than 70%, the swelling degree of stationary phase played a main role and the electroosmotic flow was decreased abnormally with the increase of ACN concentration; The electroosmotic flow was decreased with the increase of the concentration of phosphate. When the pH value was in the range of 3-9, it did not exert a significant change in electroosmotic flow. These results were consistent with the theoretical role. At the same time, five peptides were separated successfully under the optimal experimental conditions on the monolithic column for capillary electrochromatography. The column has obvious advantages in polypeptide separation and will be favorable for the protein investigation.

Synthesis and application of hypercrosslinked polymers with weak cation-exchange character for the selective extraction of basic pharmaceuticals from complex environmental water samples.

The synthesis of high specific surface area sorbents (HXLPP-WCX) in the form of hypercrosslinked polymer microspheres with narrow particle size distributions, average particle diameters around 6 microm, and weak cation-exchange (WCX) character, is described. The WCX character arises from carboxylic acid moieties in the polymers, derived from the comonomer methacrylic acid. A novel HXLPP-WCX sorbent with an attractive set of chemical and physical properties was then used in an off-line solid-phase extraction (SPE) protocol for the selective extraction of a group of basic compounds from complex environmental samples, a priority being the clean separation of the basic compounds of interest from acidic compounds and interferences. The separation power of the new sorbent for basic pharmaceuticals was compared to two commercially available, mixed-mode sorbents, namely Oasis WCX and Strata-X-CW. Under identical experimental conditions, HXLPP-WCX was found to deliver both higher capacity and better selectivity in SPE than either of the two commercially available materials. In an optimised SPE protocol, the HXLPP-WCX sorbent gave rise to quantitative and selective extractions of low microg l(-1) levels of basic pharmaceuticals present in 500 ml of river water and 250 ml of effluent waste water.

Improved performance of a biomaterial-based cation exchanger for the adsorption of uranium(VI) from water and nuclear industry wastewater.

The amine-modified polyhydroxyethylmethacrylate (poly(HEMA))-grafted biomaterial (tamarind fruit shell, TFS) carrying carboxyl functional groups at the chain end (PGTFS-COOH) was prepared and used as an adsorbent for the removal of uranium(VI) from water and nuclear industry wastewater. FTIR spectral analysis revealed that U(VI) ions and PGTFS-COOH formed a chelate complex. The adsorption process was relatively fast, requiring only 120 min to attain equilibrium. The adsorption kinetic data were best described by the pseudo-second-order equation. The equilibrium adsorption data were correlated with the Sips isotherm model. The maximum U(VI) ions uptake with PGTFS-COOH was estimated to be 100.79 mg/g. The complete removal of 10mg/L U(VI) from simulated nuclear industry wastewater was achieved by 3.5 g/L PGTFS-COOH. The reusability of the adsorbent was demonstrated over 4 cycles using NaCl (1.0M)+HCl (0.5M) solution mixture to de-extract the U(VI). The results show that the PGTFS-COOH tested is very promising for the recovery of U(VI) from water and wastewater.

Synthesis and characterization of a new inorganic cation-exchanger-Zr(IV) tungstomolybdate: analytical applications for metal content determination in real sample and synthetic mixture.

An amorphous sample of inorganic cation-exchanger Zr(IV) tungstomolybdate was prepared by mixing varying ratios of 0.1M aqueous solution of sodium tungstate and 0.1M aqueous solution of sodium molybdate into 0.1M aqueous solution of zirconium oxychloride at pH 1. This cation-exchanger was found to have a good ion-exchange capacity (2.40 mequiv.g(-1) for Na(+)), high thermal and chemical stability. A tentative structural formula was proposed on the basis of chemical composition, FTIR and thermogravimetric analysis. Distribution coefficients (K(d)) values of metal ions in various solvent systems were determined. Some important and analytically difficult quantitative binary separations viz. Ni(II)-Pb(II), Ni(II)-Zn(II), Ni(II)-Cd(II), Mg(II)-Al(III), etc. were achieved. The practical applicability of the cation-exchanger was demonstrated in the separation of Cu(II)-Zn(II) from a synthetic mixture as well as from real samples of pharmaceutical formulation and brass alloy.

New cationic exchanger support for reversible immobilization of proteins.

New tailor-made cationic exchange resins have been prepared by covalently binding aspartic-dextran polymers (e.g. MW 15 000-20 000) to porous supports (aminated agarose and Sepabeads). More than 80% of the proteins contained in crude extracts from Escherichia coli and Acetobacter turbidans have been strongly adsorbed on these porous materials at pH 5. This interaction was stronger than in conventional carboxymethyl cellulose (e.g., at pH 7 and 25 degrees C, all proteins previously adsorbed at pH 5 were released from carboxymethyl cellulose, whereas no protein was released from the new supports under similar conditions). Ionic exchange properties of such composites were strongly dependent on the size of the aspartic-dextran polymers as well as on the exact conditions of the covalent coating of the solids with the polymer (optimal conditions: 100 mg aspartic-dextran 20 000/(mL of support); room temperature). Finally, some industrially relevant enzymes (Kluyveromices lactis, Aspergillus oryzae, and Thermus sp. beta-galactosidases, Candida antarctica B lipase, and bovine pancreas trypsin and chymotrypsin) have been immobilized on these supports with very high activity recovery and immobilization rates. After enzyme inactivation, the enzyme can be fully desorbed from the support and the support could be reused for several cycles.

[Studies of chromatographic behaviors of proteins on synthesized cation-exchanger].

A chelating weak cation-exchanger has been synthesized by indirect method using domestic materials. The chromatographic performance of the synthesized packing was studied in detail, and compared with separation efficiency of commercial columns (Shim-Pack WCX-1 and Poly CATA). The chromatographic thermodynamics of proteins in weak cation-exchange system was studied over a wide temperature range. The thermodynamic parameters (deltaH0 and deltaS0) and the compensation temperature (beta) at protein denaturation were determined by their chromatographic thermal behaviors. By using the obtained standard entropy change (deltaS0), the conformational change of proteins can be judged. The compensation relationship between deltaH0 and deltaS0 was used to identify the identity of individual protein retention mechanism in chromatographic system. The interaction between chelating weak cation-exchanger and metal ions was examined. The retention mechanism of protein in metal chelating chromatography was explored.

Preparation of weak cation exchange packings based on monodisperse poly(glycidyl methacrylate- co-ethylene dimethacrylate) beads and their chromatographic properties.

The monodisperse, macroporous poly(glycidyl methacrylate- co-ethylene dimethacrylate) beads were synthesized by a single-step swelling and polymerization method. Based on this media, a weak cation exchange (WCX) stationary phase for HPLC was synthesized by a new chemically modified method. The prepared resin has advantages for biopolymer separation, high column efficiency, low column backpressure, high protein mass recovery, and good resolution for proteins. The measured bioactivity recovery for lysozyme was 98+/-5%. The dynamic protein loading capacity of the WCX packings was 17.3 mg g(-1). The experimental results show that the synthesized WCX resin has very weak hydrophobicity.

Synthesis and characterization of silica-based aliphatic ion exchangers.

The chemical literature describing preparation of aliphatic ion exchangers is limited, and although such phases are available commercially, the synthetic schemes are proprietary. The course of our research required the preparation of silica-based aliphatic cation and anion exchangers for which the desired base silica and/or ligand properties were not commercially available. We developed synthetic schemes to prepare silica-based aliphatic sulfonic acid, carboxylic acid and quaternary ammonium ion-exchange phases with active exchange capacities of 0.2-0.9 mumol/m2. Multiple techniques were used to characterize the intermediate and final phases produced in the syntheses, including Fourier transform diffuse reflectance infrared spectroscopy, spot tests, elemental analysis, acid-base titration and elution analysis.

Immobilization of penicillin G acylase on methacrylate polymers.

Macroporous weak cation-exchange methacrylate polymers were synthesized for the immobilization of penicillin G (Pen G) acylase. The role of certain factors such as pore-generating solvent, cross-linking agent, cross-linking density, and comonomer, in enzyme adsorption and expression was studied. Kerosene was a superior pore-generating solvent to paraffin oil. Ethylene glycol dimethacrylate and acrylic acid served as the best cross-linking agent and comonomer, respectively, in the systems studied. 80.3% of the activity of the enzyme adsorbed onto polymer beads prepared with 0.05 mol of acrylic acid (polymer PM-39) was expressed. Properties of the Pen G acylase, immobilized on PM-39 by adsorption and cross-linking with glutaraldehyde (IME-PM-39) were studied. The optimum pH, optimum temperature and Km of Pen G acylase shifted from 8.0 to 7.5-7.8, 50 degrees C to 55 degrees C and 0.038 mol dm-3 to 2.4-3.0 mol dm-3, respectively, as a result of immobilization on PM-39. IME-PM-39 was used repeatedly for 15 cycles in the production of 6-amino penicillanic acid (6-APA).

High-performance cation-exchange chromatography of proteins.

Approximately one-third of all proteins reported in the literature have a pI sufficiently high to be resolved by cation-exchange chromatography. This paper reports the preparation and use of new high-performance polymeric-bonded-phase cation-exchange columns. Starting from a very stable, covalently bonded polyamide coating on microparticulate silica, simple derivatization produces a versatile cation-exchange material useful for separations traditionally performed on classical carboxymethylated soft gel supports. Column behavior was monitored using chymotrypsinogen, cytochrome c, and lysozyme as standards. The polymeric bonded phase was stable to pH 2.5 and exhibits enhanced selectivity for proteins due to a slight hydrophobic character of the matrix. Several separations of biological interest that demonstrate the utility of these small cation-exchange columns for modern biochemical separations are shown.