Anion Exchange Properties Research Articles

Anion-directed assemblies of cationic metal-organic frameworks based on 4,4'-bis(1,2,4-triazole): syntheses, structures, luminescent and anion exchange properties.

Three cationic metal-organic frameworks (MOFs), Ag(btr)·PF6·0.5CH3CN (1), Ag2(btr)2(H2O)·2CF3SO3·H2O (2), and Ag2(btr)2(NO3)·NO3 (3), were prepared from reaction of 4,4'-bis(1,2,4-triazole) (btr) with silver salts containing different anions. Complex 1 is a three-dimensional (3-D) framework constructed from tetrahedral-shaped nanoscale coordination cages with PF6(-) as counteranions. 2 and 3 are 3-D architectures containing 1-D channels, in which charge-balancing CF3SO3(-) and NO3(-) are located in their respective channels. Luminescent emission of 1-3 shows an obvious red shift compared with the btr ligand. Anion exchange studies show that 1 is able to selectively exchange MnO4(-) in aqueous solution with a modest capacity of 0.56 mol mol(-1); the luminescent emission of 1 is quickly quenched upon MnO4(-) exchange.

Novel anion receptors: hybrid materials based on quaternary ammonium salts for selective extraction of dichromate ions

Novel hybrid materials were obtained by modification of three (poly)amine-appended mesoporous silica gels. For all matrices of different side chain lengths, the process proceeded with excellent modification rates. The free analogues of these hybrid materials, podand-type receptors, were also prepared employing a very similar procedure. The organosilicas synthesized were characterized by NMR, infrared spectroscopy, and semi-empirical methods. Their anion exchange properties were conveniently investigated using precise, but also time and cost-efficient titration experiments, and the products were found to be powerful complexing agents for dichromate ions.

A ‘kagome dual’ (kgd) sheet based on triangular rigid ligand: Synthesis, structure, photoluminescence and anion exchange properties

A cadmium coordination polymer with ‘Kagomé dual’ (kgd) sheet structure, {[Cd(tipa)2]·2NO3·5DMF}n (1), has been synthesized by employing an elongated triangular rigid N-containing ligand tris(4-(1H-imidazol-yl)phenyl)amine (tipa) and structurally characterized by X-ray single-crystal diffraction. The Cd(II) ion is six coordinated with N atoms from tipa ligands, forming a CdN6 octahedron geometry. The tridentate tipa ligand connects the Cd(II) ions into a 2D sheet. Topologically, if the triangular tipa ligand and the Cd(II) ions are regarded as 3- and 6-connected nodes respectively, the overall 2D sheet can be simplified to a (3,6)-connected kgd net with a Schläfli symbol of (43)2(46·66·83). Moreover, the photoluminescence at 298 and 77K and anion exchange properties of 1 were also discussed.

HPLC/ESI-MSn method for non-amino bisphosphonates: Application to the detection of tiludronate in equine plasma

Tiludronate is a non-nitrogen-containing biphosphonate drug approved in equine veterinary medicine for the treatment of navicular disease and bone sparvin in horse. Its hydrophilic properties and its strong affinity for the bone have made the control of its use quite difficult. After an initial step of method development in plasma and urine, due to a strong matrix effect and erratic detection in urine, the final method development was conducted in plasma. After addition of (3-trifluoromethylphenyl) thiomethylene biphosphonic acid as internal standard, automated sample preparation consisted of a filtration on a Nexus cartridge followed by a Solid Phase Extraction on an Oasis WAX cartridge with weak anion exchange properties. After methylation of the residue with trimethyl orthoacetate (TMOA), analysis was conducted by HPLC/ESI-MS(n) on a LTQ mass spectrometer. The method has been validated with a LOD and LOQ of respectively 1 and 2.5ng/mL. Using a weighting factor of 1/concentration(2), a linear model was suitable in the range of 2.5 up to 500ng/mL. Precision and accuracy data determined at two concentrations were satisfactory (i.e. less than 15%). Carryover would have been a problem but this has finally been fixed using the additional steps of washing during robotised SPE extraction and analysis on both the autosampler and the analytical column. The method was successfully employed for the first time to the quantification of tiludronate in plasma samples collected from horses treated with Tildren™ (Intravenous administration at the dose of 0.1mg/kg/day for 10 days).

Solid-phase extraction of PFOA and PFOS from surface waters on functionalized multiwalled carbon nanotubes followed by UPLC–ESI-MS

This is the first report on the analytical application of multiwalled carbon nanotubes (MWCNTs) as solid-phase extraction (SPE) sorbents for determination in surface waters, at the nanograms per litre level, of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), the two predominant contaminants among the perfluorinated compounds detected. After the preconcentration step, the quantification was achieved by ultraperformance liquid chromatography-electrospray ionization mass spectrometry. To increase the extraction efficiency towards these amphiphilic compounds, MWCNTs were derivatized with amino-terminated alkyl chains, thus producing a mixed-mode material (MWCNT-R-NH2) combining hydrophobic affinity and anion-exchange properties. Experiments with distilled, tap and river water (pH 3) spiked at different concentrations (10, 15, 30, 100, 200 and 500 ng L(-1)) provided absolute recoveries in the range 71-102% (n = 3, relative standard deviations less than 10%). Analytes were eluted in a single fraction with 6 mL methanol (3 × 10(-4) M NaOH). The within-laboratory reproducibility of the MWCNT-R-NH2 SPE sorbent was evaluated with raw river water, and relative standard deviations less than 15% were obtained (n = 4). Preconcentration factors up to 125 (500-mL sample) made it possible to quantify PFOA and PFOS at low nanograms per litre levels in naturally contaminated river water. The method quantification limits of 10 ng L(-1) for PFOA and 15 ng L(-1) for PFOS were well below the advisory levels for drinking and surface waters. Comparison with non-derivatized MWCNTs highlighted the role of functionalization in improving the adsorption affinity towards these contaminants. MWCNT-R-NH2 maintained their extraction capability for at least eight repeated adsorption/desorption cycles.

Visually Recognizable Anion Exchange of a Three-dimensional Copper-based Interpenetrated Porous Coordination Polymer

Abstract A new three-dimensional copper-based interpenetrated porous coordination polymer (PCP) was synthesized using 1,2-di(4-pyridyl)ethylene (bpe), which is an N-donor neutral organic linker. The PCP has a cationic framework because all counter BF4− anions present as guest species to compensate the positive charge of the framework. The PCP shows anion-exchange properties for halogen ions, which can be recognized visually.

Zinc(ii) and cadmium(ii) metal–organic frameworks with 4-imidazole containing tripodal ligand: sorption and anion exchange properties

The use of a 4-imidazole containing tripodal ligand 1,3,5-tri(1H-imidazol-4-yl)benzene (H3L) enabled isolation of two three-dimensional (3D) porous metal-organic frameworks (MOFs) [Zn(HL)] · solvent (1) and [Cd(H3L)2](ClO4)2 · 10.5H2O (2) featuring 4,4- and 3,6-connected nets related to the structures of ecl and pyrite, respectively. Framework 1 has 3D channels based on Zn-Im(-) (Im(-) = imidazolate) moieties due to partial deprotonation of the 1H-imidazol-4-yl groups of H3L while porous framework 2 is constructed by the coordination of neutral H3L ligands with Cd(II). Desolvated solid 1' showed remarkable uptake for CO2, N2, H2, CH4 gases as well as the volatile organic vapor of MeOH, EtOH, i-PrOH and C6H6, significantly, exhibiting temperature dependent selective gas sorption for CO2 over N2. Grand Canonical Monte Carlo (GCMC) simulations were performed to elucidate the mechanism of the selective gas adsorption. Cage-like motifs are found in pyrite-net 2, in which ClO4(-) anions are hosted, and the results of IR, elemental analysis and PXRD measurements confirm that 2 has a reversible anion exchange property among perchlorate, nitrate and nitrite anions.

Enrichment specificity of micro and nano‐sized titanium and zirconium dioxides particles in phosphopeptide mapping

Owning to their anion-exchange properties, titanium and zirconium dioxides are widely used in phosphopeptide enrichment and purification protocols. The physical and chemical characteristics of the particles can significantly influence the loading capacity, the capture efficiency and phosphopeptide specificity and thus the outcome of the analyses. Although there are a number of protocols and commercial kits available for phosphopeptide purification, little data are found in the literature on the choice of the enrichment media. Here, we studied the influence of particle size on the affinity capture of phosphopeptides by TiO2 and ZrO2. Bovine milk casein derived phosphopeptides were enriched by micro and nanoparticles using a single-tube in-solution protocol at different peptide-to-beads ratio ranging from 1 : 1 to 1 : 200. Unsupervised hierarchical cluster analysis based on the whole set of Matrix Assisted Laser Desorption/Ionization time-of-flight mass spectra of the phosphopeptide enriched samples revealed 62 clustered peptide peaks and shows that nanoparticles have considerably higher enrichment capacity than bulk microparticles. Moreover, ZrO2 particles have higher enrichment capacity than TiO2. The selectivity and specificity of the enrichment was studied by monitoring the ion abundances of monophosphorylated, multiphosphorylated and non-phosphorylated casein-derived peptide peaks at different peptide-to-beads ratios. Comparison of the resulting plots enabled the determination of the optimal peptide-to-beads ratios for the different beads studied and showed that nano-TiO2 have higher selectivity for phosphopeptides than nano-ZrO2 particles.

Preparation of Mg–Al layered double hydroxide doped with Fe2+ and its application to Cr(VI) removal

Mg–Al layered double hydroxide (Mg–Al LDH) doped with Fe2+ was prepared by dropwise addition of a mixed solution of MgCl2, FeCl2, and AlCl3 to NaOH solution at a constant pH. The Fe2+-doped LDH was found to be able to remove Cr(VI) from an aqueous solution through the anion exchange of Cr2O72- with the intercalated Cl−, the production of Cr(OH)3, and the adsorption of Cr2O72- on the surface of the produced FeO(OH). The excellent performance of this LDH for Cr(VI) removal is caused by both the anion exchange properties of Mg–Al LDH and the reducing activity of the Fe2+ doped into the Mg–Al LDH. This process can be considered to occur through Langmuir-type adsorption, and the maximum adsorption amount and equilibrium adsorption constant are 12.5mmolg−1 and 242.1, respectively.

Preparation and Characterization of Fe-, Co-, and Ni-Containing Mg-Al-Layered Double Hydroxides

AbstractSyntheses of Fe-, Co-, and Ni-containing Mg-Al-layered double hydroxides (LDHs) are described here because Fe, Co, and Ni represent the major constituents in steel containers used for storing spent nuclear fuel. Much evidence exists for the formation of LDHs during the corrosion of such containers under repository-relevant conditions. Because of their anion-exchange properties, LDHs can be considered as materials with the potential to retain and immobilize anionic radionuclides. Evaluation of the thermodynamic properties of LDHs is essential for reliable prediction of their behavior (solubility, anion exchange properties) in geochemical environments. The impact on the thermodynamic properties of the isostructural incorporation of divalent cations into the LDH was the main focus of the present study.Mg-Al-Cl-LDH and the Fe-, Co-, and Ni-doped LDHs were synthesized by the co-precipitation method and then characterized (using powder X-ray diffraction (PXRD), extended X-ray absorption fine structure (EXAFS), X-ray absorption near edge structure (XANES), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy energy-dispersive X-ray spectroscopy (SEM-EDX), and thermogravimetric analyses (TGA)).The PXRD and EXAFS analyses indicated that all synthesized samples were pure LDHs where Co, Ni, and Fe were incorporated isostructurally. The EXAFS and XANES results demonstrated that Ni and Co were incorporated as divalent cations and Fe as a trivalent cation. Thermodynamic calculations were performed assuming an equilibrium state between aqueous solutions and corresponding precipitates after synthesis. The first estimates of the molar Gibbs free energies for Fe-, Co-, and Ni-containing LDHs at 70ºC were provided. The calculated Gibbs free energy of the pure Mg-Al-LDH (-3629 kJ/mol) was slightly less than those for Fe-, Co-, and Ni-containing compositions (-3612±50, -3604±50, -3593±50kJ/mol).

Applications versus properties of Mg–Al layered double hydroxides provided by their syntheses methods: Alkoxide and alkoxide-free sol–gel syntheses and hydrothermal precipitation

A tremendous number of studies have examined layered double hydroxides (LDH) for their technological applications in the ion exchange removal of toxic ions, recovery of valuable substances, catalysis, CO2 capture, as a layered host for storage/delivery of biologically active molecules, additives to plastics and building materials, and other functions. Numerous publications always conclude that the materials (prepared, as a rule, using the oldest synthesis method) are very promising for each investigated application; however, the main chemical industries producing these materials advertise them mainly (or only) as plastic additives. The authors performed extensive research using many of the appropriate methods to compare the structure, surface and adsorptive properties of three Mg–Al LHDs produced by advanced synthesis methods. One industrial sample (by Sasol, Germany) prepared by the alkoxide sol–gel method and two novel Mg–Al LDHs synthesised in-house by alkoxide-free sol–gel and hydrothermal precipitation approaches were investigated. Reasons for the very different adsorptive selectivity of the three LDHs towards arsenate, selenate, phosphate, arsenite and selenite have been provided, highlighting the role of speciation of the interlayer carbonate, aluminium, magnesium, interlayer hydration and moisture content in the adsorptive selectivity towards each toxic anion. This work is the first report presenting the regularities of the LDHs structure, surface and anion exchange properties as a function of their syntheses method. It establishes the links to potential technological applications of each investigated LDH and explains the necessary properties required to make the technological application cost-effective and efficient. The paper might accelerate industrial applications of these advanced materials.

Release behavior and toxicity profiles towards A549 cell lines of ciprofloxacin from its layered zinc hydroxide intercalation compound

BackgroundLayered hydroxides salts (LHS), a layered inorganic compound is gaining attention in a wide range of applications, particularly due to its unique anion exchange properties. In this work, layered zinc hydroxide nitrate (LZH), a family member of LHS was intercalated with anionic ciprofloxacin (CFX), a broad spectrum antibiotic via ion exchange in a mixture solution of water:ethanol.ResultsPowder x-ray diffraction (XRD), Fourier transform infrared (FTIR) and thermogravimetric analysis (TGA) confirmed the drug anions were successfully intercalated in the interlayer space of LZH. Specific surface area of the obtained compound was increased compared to that of the host due to the different pore textures between the two materials. CFX anions were slowly released over 80 hours in phosphate-buffered saline (PBS) solution due to strong interactions that occurred between the intercalated anions and the host lattices. The intercalation compound demonstrated enhanced antiproliferative effects towards A549 cancer cells compared to the toxicity of CFX alone.ConclusionsStrong host-guest interactions between the LZH lattice and the CFX anion give rise to a new intercalation compound that demonstrates sustained release mode and enhanced toxicity effects towards A549 cell lines. These findings should serve as foundations towards further developments of the brucite-like host material in drug delivery systems.

Anion-exchange properties of nickel–aluminum layered double hydroxide prepared by liquid phase deposition

The optimum coordination structure of Ni–fluoro complexes for the preparation of Ni–Al LDH by LPD process and the diverse anion-exchange properties of as-deposited Ni–Al on α-alumina powder were quantitatively evaluated for the industrial application of new positive material for alkali secondary batteries. The [NiF6−x−y(NH3)x(OH−)y]n+ was more suitable than [NiF6]4− as the precursor of the deposition of Ni–Al LDH in the LPD reaction, and the improved LPD reaction achieved the synthesis of high purity and high crystallinity Ni–Al LDH. All anion-exchanged Ni–Al LDHs for OH−–, Cl−–, SO42−–, and CH3COO−–forms kept the high crystallinity and showed the enlargement of interlayer distances. The tilting angle of the intercalated CH3COO− anions was about 15°. Anion-exchange capacity remained constant at a minimum of 0.8 meq g−1 in pH >10, increased as pH decreased, and reached a maximum of 8 meq g−1 at pH 2. Anion-exchange of OH−–form of Ni–Al LDH was accelerated by the neutralization of hydroxide ions in interlayers, in addition, the anion-exchange capacity and the crystallinity of Ni–Al LDH could be controlled by the amount of doped aluminum ions.

Synthesis, Structure, and Properties of a Zinc Coordination Polymer With Flexible Ligand 1,4-Bis(1,2,4-triazol-1-ylmethyl)-2,3,5,6-tetramethylbenzene

A new zinc coordination polymer, {[Zn(tmtz)2(H2O)2](NO3)2}n (1) (tmtz = 1,4-bis(1,2,4-triazol-1-ylmethyl)-2,3,5,6-tetramethyl benzene), has been synthesized and characterized by elemental analysis, IR, and single-crystal X-ray diffraction. 1 consists of one-dimensional cationic chains [Zn(tmtz)2(H2O)2]n containing alternative two kinds of perpendicular rings [Zn2(tmtz)2]. Each [Zn2(tmtz)2] ring encapsulates two nitrate anions through the O-H…O hydrogen bond interactions. Each cationic chain is surrounding by four nearest identical chains and four second nearest chains. A three-dimensional supramolecular network is constructed through the benzene ring π···π stacking interactions. The interesting properties of inverse anion exchange were observed. Also, the luminescence and thermal stability were investigated. Supplemental materials are available for this article. Go to the publisher's online edition of Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry to view the supplemental file.

Thermal characterization of polymeric anion exchangers with a dendrimeric structure

The thermal properties of new anion exchangers prepared via the grafting process to polymeric particles having hydroxyl groups on their surface were evaluated by thermogravimetry and differential scanning calorimetry. The support microspheres were copolymers of 1,4-di(2-hydroxy-3-methacryloyloxypropoxy)benzene (1,4 DMH) and trimethylolpropane trimethacrylate (TRIM). They were coated with polymeric layers formed by condensation polymerization of primary amines with diepoxides. Synthesized copolymers of methylamine and 1,4-butanedioldiglycidyl ether have a dendrimer structure. By TG/FTIR/MS, it was observed that new dendrimeric materials exhibited one stage of mass loss with T max1 400 °C, connected with degradation of organic layers. DSC and TG experiments showed that water molecules are absorbed on the materials surface. The synthesized anion exchangers exhibited good thermal stability, suitable for their use in chromatographic experiments carried out with higher temperatures.

Ionic liquid–kaolinite nanohybrid materials for the amperometric detection of trace levels of iodide

A nanohybrid kaolinite material with anion exchange properties was obtained by the grafting of an ionic liquid in the interlayer spaces of kaolinite. It was used successfully for the amperometric detection of iodide in aqueous solution and tap water after a pre-concentration step, with a detection limit of 1.5 × 10(-7) M. This electrode has an excellent stability. Its selectivity was tested in the presence of several anions.

Zn2+ substitution effects in layered double hydroxide (Mg(1−x)Znx)2Al: textural properties, water content and ionic conductivity

Recently, layered double hydroxides (LDHs) have been studied as anion conductors for fuel cell applications because of their anion exchange properties and better thermal stability (up to 150 °C) than those of anion exchange polymers. However, the conductivity of the LDHs is very low, under 10−3 S cm−1 at room temperature, and the mechanism of anion conduction has not been explained clearly. In the present study, we investigate the physical properties of LDHs affecting anion conductivity by synthesizing trimetallic LDHs, (Mg(1−x)Znx)2Al–CO32− with different ratios of Mg2+ and Zn2+. The amount of anion in these LDHs and the particle size were kept the same in all LDHs by controlling the amount of Al3+ and the synthesis methods, respectively. The LDHs synthesized were characterized using techniques such as XRD, ICP-AES, TEM, zeta-potential measurements, XPS and TG and also by measuring the adsorbed water content in a range of temperatures and humidities. The ratio of Zn2+ to divalent metal in the LDH framework affected the interlayer distance and the water content. Among the series of LDHs of (Mg(1−x)Znx)2Al–CO32−, the ones with a Zn2+ : divalent metal ratio of around 0.5 presented the largest interlayer distance, the largest amount of adsorbed water and the highest ion conductivity. Interestingly, the anion conductivity showed a good correlation with the interlayer distance and the adsorbed water content. The anion conductivity increased as the interlayer distance increased and also as the amount of adsorbed water increased. These results imply that the anion conduction may occur primarily in the interlayer space and the adsorbed water assists the anion conduction.

Layered-double-hydroxide-modified electrodes: electroanalytical applications

Two-dimensional inorganic solids, such as layered double hydroxides (LDHs), also defined as anionic clays, have open structures and unique anion-exchange properties which make them very appropriate materials for the immobilization of anions and biomolecules that often bear an overall negative charge. This review aims to describe the important aspects and new developments of electrochemical sensors and biosensors based on LDHs, evidencing the research from our own laboratory and other groups. It is intended to provide an overview of the various types of chemically modified electrodes that have been developed with these 2D layered materials, along with the significant advances made over the last several years. In particular, we report the main methods used for the deposition of LDH films on different substrates, the conductive properties of these materials, the possibility to use them in the development of membranes for potentiometric anion analysis, the early analytical applications of chemically modified electrodes based on the ability of LDHs to preconcentrate redox-active anions and finally the most recent applications exploiting their electrocatalytic properties. Another promising application field of LDHs, when they are employed as host structures for enzymes, is biosensing, which is described considering glucose as an example.

Chemical and photochemical formation of gold nanoparticles supported on viologen-functionalized SBA-15

Viologen-functionalized SBA-15 was successfully prepared and used for the chemical and photochemical formation of supported gold nanoparticles. The anion exchange properties of viologen moieties were explored and AuCl4− anion were adsorbed and retained by electrostatic interactions inside the substrate porous structure. Subsequently, the formation of gold nanoparticles was accomplished by two different routes: (i) by chemical reduction, using NaBH4 as reducing agent; (ii) photochemical reduction, utilizing the redox properties of the grafted viologen groups under UV irradiation. Diffuse reflectance measurements and TEM images revealed that the chemical reduction generated gold nanospheres dispersed inside the host mesopores, while photochemical reduction produced gold nanorods.

Development of a new multi-residue laser diode thermal desorption atmospheric pressure chemical ionization tandem mass spectrometry method for the detection and quantification of pesticides and pharmaceuticals in wastewater samples

A new solid phase extraction (SPE) method coupled to a high throughput sample analysis technique was developed for the simultaneous determination of nine selected emerging contaminants in wastewater (atrazine, desethylatrazine, 17β-estradiol, ethynylestradiol, norethindrone, caffeine, carbamazepine, diclofenac and sulfamethoxazole). We specifically included pharmaceutical compounds from multiple therapeutic classes, as well as pesticides. Sample pre-concentration and clean-up was performed using a mixed-mode SPE cartridge (Strata ABW) having both cation and anion exchange properties, followed by analysis by laser diode thermal desorption atmospheric pressure chemical ionization coupled to tandem mass spectrometry (LDTD-APCI-MS/MS). The LDTD interface is a new high-throughput sample introduction method, which reduces total analysis time to less than 15s per sample as compared to minutes with traditional liquid-chromatography coupled to tandem mass spectrometry (LC–MS/MS). Several SPE parameters were evaluated in order to optimize recovery efficiencies when extracting analytes from wastewater, such as the nature of the stationary phase, the loading flow rate, the extraction pH, the volume and composition of the washing solution and the initial sample volume. The method was successfully applied to real wastewater samples from the primary sedimentation tank of a municipal wastewater treatment plant. Recoveries of target compounds from wastewater ranged from 78% to 106%, the limit of detection ranged from 30 to 122ngL−1 while the limit of quantification ranged from 90 to 370ngL−1. Calibration curves in the wastewater matrix showed good linearity (R2≥0.991) for all target analytes and the intraday and interday coefficient of variation was below 15%, reflecting a good precision.