Selective Separation of Thorium Using Ion Imprinted Chitosan‐Phthalate Particles via Solid Phase Extraction

Abstract

We have studied a new method for the preparation of Th(IV)‐imprinted chitosan‐phthalate particles, which can considerably enhance the adsorption capacity and selectivity of thorium ions. In this study, chitosan‐phthalate was used as the complexing monomer, Th(IV) as template, epichlorohydrin as crosslinking agent. Initially, chitosan was modified with phthalic anhydrides and complex formation occured between carboxylic acid functional groups and Th(IV) ions. Secondly, particles were crosslinked with epichlorohydrin. After the removal of Th(IV) ions, thorium solid phase extraction (SPE) on the Th(IV) ion‐imprinted particles from aqueous solutions containing their different amounts, selectivity study of thorium versus other interfering metal ions mixture which are Fe³⁺, La³⁺, and Mn²⁺ and distribution and selectivity coefficients were reported here. A comparison of the selectivity coefficient of Th(IV)‐imprinted chitosan‐phthalate particles with the selectivity coefficient of non‐imprinted polymers showed that the imprinted matrix for Th(IV)/Fe(III), Th(IV)/La(III) and Th(IV)/Mn(II) was 8.35, 8.75 and 10.81 times greater than non‐imprinted matrix, respectively.     

Molecular Imprinted Polymer of Methacrylic Acid Functionalised β-Cyclodextrin for Selective Removal of 2,4-Dichlorophenol

This work describes methacrylic acid functionalized β-cyclodextrin (MAA-βCD) as a novel functional monomer in the preparation of molecular imprinted polymer (MIP MAA-βCD) for the selective removal of 2,4-dichlorophenol (2,4-DCP). The polymer was characterized using Fourier Transform Infrared (FTIR) spectroscopy, Brunauer-Emmett-Teller (BET) and Field Emission Scanning Electron Microscopy (FESEM) techniques. The influence of parameters such as solution pH, contact time, temperature and initial concentrations towards removal of 2,4-DCP using MIP MAA-βCD have been evaluated. The imprinted material shows fast kinetics and the optimum pH for removal of 2,4-DCP is pH 7. Compared with the corresponding non-imprinted polymer (NIP MAA-βCD), the MIP MAA-βCD exhibited higher adsorption capacity and outstanding selectivity towards 2,4-DCP. Freundlich isotherm best fitted the adsorption equilibrium data of MIP MAA-βCD and the kinetics followed a pseudo-second-order model. The calculated thermodynamic parameters showed that adsorption of 2,4-DCP was spontaneous and exothermic under the examined conditions.     

Extraction of Parabens from Water Samples Using Cloud Point Extraction with a Non-Ionic Surfactant with β-Cyclodextrin as Modifier

A cloud point extraction process using a silicone non-ionic surfactant to extract selected parabens compounds from water samples was investigated using reversed phase high performance liquid chromatography. The cloud point extraction process, in the presence of β-cyclodextrin (β-CD) as a modifier, is a new extraction process which was optimized with five parameters, i.e. salt concentration, pH of the solution, temperature, surfactant concentration and β-CD concentration. The developed method with the β-CD modifier results in an excellent performance on detection of parabens from water samples with limits of detection in the range of 0.017–0.043 μg/L and percentage recoveries from 90.5 to 98.9 %.     

Head Space—Solid Phase Micro Extraction Profile of Volatile Organic Compounds Emitted from Parquet Samples

The potential health risks posed by volatile organic compounds (VOCs) in homes are of concern. There is little information on indoor VOC emissions from wood flooring, called parquet. Six parquet samples were examined for VOCs in this preliminary study using Head Space—Solid Phase Micro Extraction (SPME) gas chromatography, a powerful and versatile analytical method which has been only minimally employed previously in wood chemistry. Prefinished composite samples released the highest levels of VOCs, mainly due to adhesives and finishes, with acetic acid the main component released from the oak component. As some VOCs from parquet present a health hazard, more comprehensive studies employing the SPME technique described herein are needed.     

Modification and Evaluation of Non‐Polar Sorbents for Solid‐Phase Extraction

Abstract

Modification of packings for solid‐phase extraction through high‐frequency low‐temperature plasma treatment is a new method to obtain a wide variety of sorbents. This method is still in the process of investigation and application. In this study, several commercial sorbents have been modified in high‐frequency low‐temperature plasma with the mixed hydrogen/benzene system. The solvation parameter model is used to characterize the sorption properties of commercially available and plasma treated sorbents for solid‐phase extraction. Chromatographic test mixtures from the literature were used to probe hydrophobicity, free silanol interactions and shape selectivity of the sorbents. The physical and retention properties of the plasma treated sorbents indicate their suitability to be used in solid‐phase extraction. Some suggestions concerning the possible practical application of the newly obtained sorbents have been made.     

Micelle‐Mediated Extraction for Direct Spectrophotometric Determination of Trace Uranium(VI) in Water Samples

Abstract

The possibility of using Dibenzoylmethane (DBM) for uranium(VI) concentrating by the way of micellar extraction at cloud point temperature and later spectrophotometric determination was investigated. Under the optimum conditions, preconcentration of 50 mL of water samples in the presence of 0.2% (w/v) octylphenoxypolyethoxy ethanol (Triton X‐114), 2×10^?4 mol L^?1 DBM and 2×10^?3 mol L^?1 buffer solution (pH=9) gave a limit of detection 11 ng mL^?1, and the calibration graph was linear in the range of 15–300 ng mL^?1. The recovery under optimum working conditions was higher than 98%.

The proposed method has been applied to the spectrophotometric determination of uranium(VI) in natural water samples after cloud point extraction with satisfactory results.     

Electrochemical Sensor for Detection of Trichlorfon Based on Molecularly Imprinted Sol–Gel Films Modified Glassy Carbon Electrode

Thin films of molecularly imprinted sol–gel polymer with specific binding sites for trichlorfon were prepared, fixed on glassy carbon electrodes and used as recognition material. The binding characteristic of the imprinted films to trichlorfon was evaluated by equilibrium binding experiments; and, the morphology was studied by scanning electronic microscope. A novel electrochemical sensor for determination of trichlorfon was developed based on the reaction between trichlorfon and the molecularly imprinted sol–gel film, which was a modified glassy carbon electrode. The sensor displayed excellent selectivity and high sensitivity. The linear response range of the sensor was 10⁻⁸ –10⁻⁶ g mL⁻¹, and the limit of detection was 2.8 × 10⁻⁹ g mL⁻¹. The relative standard deviation for the determination of 10⁻⁷ g mL⁻¹ trichlorfon was 3.5%. The sensor was applied to the determination of trichlorfon in vegetables with satisfactory results.     

Ion Imprinted Polymer Solid Phase Extraction (IIP‐SPE) for Preconcentrative Separation of Erbium(III) From Adjacent Lanthanides and Yttrium

Abstract

Erbium(III) ion imprinted polymer (IIP) materials were prepared by photochemical polymerization of the ternary complex, Erbium(III)—5,7‐dichloroquinoline‐8‐ol‐4‐vinylpyridine, with methyl methacrylate (functional monomer) and ethylene glycol dimethacrylate (crosslinking monomer) in the presence of 2,2′‐azobisisobutyronitrile (initiator). The synthesis was carried out in 2‐methoxy ethanol (porogen) medium and the resultant material was filtered, dried and powdered to form unleached polymer particles. The imprint ion (erbium(III)) was removed by stirring the above particles with 6 mol/l HCl to obtain leached polymer particles. These leached particles are termed erbium(III) ion imprinted polymer (IIP) particles as it selectively rebind erbium(III) ions. Non‐imprinted/control polymer (CP) particles were similarly prepared without the imprint ion. CP and unleached and leached IIP particles were characterized by XRD, microanalysis, and UV‐visible spectrophotometric studies. Various parameters that influence ion imprinted polymer—solid phase extraction such as pH, weight of polymer particles, preconcentration time, elution time, eluent volume, and aqueous phase volume were varied and optimal conditions for each parameter for quantitative enrichment of erbium(III) were established. The selectivity coefficients of erbium(III) ion over Y, Dy, Ho and Tm were compared with separation factors reported for two of the best liquid—liquid extractants viz. di‐2‐ethylhexyl phosphoric acid and 2‐ethylhexyl‐ethylhexyl phosphate.     

Solid Phase Extraction and Preconcentration of Trace Heavy Metal Ions in Natural Water with 2,2′‐Dithiobisaniline Modified Amberlite XAD‐2

Abstract

A solid phase extraction and preconcentration methodology utilizing a new chelating resin is described for the separation of Cd, Ni, Co, Cu, and Zn. The chelating resin matrix was prepared by covalently linking 2,2′‐dithiobisaniline synthesized from 2‐aminothiophenol with the benzene ring of polystyrene‐divinylbenzene resin Amberlite XAD‐2 through a –N?N– group. Its adsorption and preconcentration behavior for Cd, Ni, Co, Cu, and Zn in aqueous solution was studied using batch and column procedures in detail. The newly designed resin quantitatively adsorbs Cd, Ni, Co, Cu, and Zn above pH 5.0. Subsequent elution with 2 M HCl readily strips the sorbed metal ions from the resin. The sorption capacity is 360, 230, 170, 200, and 150 mol g^?1 for Cd, Ni, Co, Cu, and Zn, respectively. Their preconcentration factors are 80–200. The time for 80% sorption was less than 10 min for all five metal ions. The effects of electrolytes on the preconcentration were also investigated with the recoveries >95%. The procedure was validated by analysis of a standard reference river sediment material (GBW 08301 China). The developed method was successively utilized for the determination of Cd, Ni, Co, Cu, and Zn in tap water and river water by flame atomic absorption spectrometry (FAAS) after column SPE and preconcentration. The 3σ detection limits for these metal ions were found to be 0.10, 0.34, 0.42, 0.16, and 0.52 g L^?1, respectively. The relative standard deviation was <10% for the determination of 10 g each of Cd, Ni, Co, Cu, and Zn in a 100 mL water sample.     

Kinetic Study for Biphasic Recognition Chiral Extraction of Naproxen Enantiomers with Hydrophobic L-iso-butyl Tartrate and Hydrophilic Hydroxypropyl-β-Cyclodextrin

The kinetics of biphasic recognition chiral extraction of naproxen (HA) enantiomers was investigated to determine the extraction mechanism, with hydrophobic L-iso-butyl tartrate (L-IBTA) in the organic phase and hydrophilic hydroxypropyl-β-cyclodextrin (HP--CD) in the aqueous phase. The two-phase homogeneous reaction model was selected over the interfacial reaction model, because there is a clear physical solubility of naproxen enantiomers in both the aqueous phase and the organic phase. The reactions between the HA enantiomers and L-iso-butyl tartrate in a stirred cell fall in Regime 3; the extraction is accompanied by two fast chemical reactions in the diffusion film. The reactions have been found to be first order with respect to HA enantiomers and second order with respect to L-IBTA. The forward rate constants for S-HA and R-HA are 1.26?×?10^?4 mol^?2 m⁶ s^?1 and 2.52?×?10^?4 mol^?2 m⁶ s^?1, respectively. With the increase of HP--CD concentration in the aqueous phase, high enantioselectivity was obtained, but the extraction rates decreased. These data will be useful in the design of extraction processes.     

Homogeneous Liquid–Liquid Extraction and Determination of Cobalt,Copper, and Nickel in Water Samples by Flame Atomic Absorption Spectrometry

Abstract

A simple and effective homogeneous liquid–liquid extraction method has been used for the simultaneous extraction and preconcentration of cobalt, copper, and nickel after the formation of complex with 4‐benzylpiperidinedithiocarbamate potassium salt (K‐4‐BPDC), and later they were determined by flame atomic absorption spectrometry (FAAS) using (water/tetrabutylammonium ion (TBA⁺)/chloroform) as a ternary component system. The phase separation phenomenon occurred by an ion‐pair formation of TBA⁺ and perchlorate ion. After the optimization of complexation and extraction conditions ([K‐4‐BPDC]=2.0×10^?4 mol l^?1, [TBA⁺]=2.0×10^?2 mol l^?1, [CHCl₃]=60.0 µl, [ClO₄ ^?]=2.0 ×10^?2 mol l ^?1 and pH=6.0), a preconcentration factor of 200 was obtained for only 10 ml of the sample.

The analytical curves were linear in the range of 20–1500, 15–2000, 35–1600 µg l^?1 and the limits of detection were 10, 5, and 15 µg l^?1 for Co²⁺, Cu²⁺, and Ni²⁺, respectively. The proposed method was applied for the extraction and determination of Co²⁺, Cu²⁺, and Ni²⁺ in natural water samples with satisfactory results.     

A Simple and Highly Selective Biomimetic Oxidation of Alcohols with Hypervalent Iodine(III) Reagent Catalyzed by β-Cyclodextrin in Water

Abstract  

A simple, mild and highly efficient biomimetic oxidation of alcohols to the corresponding aldehydes or ketones with hypervalent iodine(III) reagent catalyzed by β-cyclodextrin was reported. β-cyclodextrin serves as a biological catalyst to enhance the reaction remarkably. The oxidation proceeded in water to afford aldehydes or ketones in excellent yields and high selectivity without remarkable over-oxidation to carboxylic acids. Selective oxidation of primary alcohols in the presence of secondary alcohols was also achieved. A possible mechanism for the oxidation was proposed.     

β-Cyclodextrin Based Nanosponge as a Biodegradable Porous Three-Dimensional Nanocatalyst in the One-Pot Synthesis of N- Containing Organic Scaffolds

The motivation behind the present study was to develop an application of β-cyclodextrin-based nanosponges with the tiny mesh-like structure as porous three-dimensional nanocatalyst in the one-pot three component condensations of various aromatic aldehydes with activated methylene compounds such as dimedone, thiobarbituric acid, 4-hydroxycoumarin, 4-hydroxy-6-methyl-2-pyrone and nucleophiles including indole and amines. This nanosponge catalyst afforded the privileged N- containing organic scaffolds as key intermediates in pharmaceutical chemistry in very short reaction times.

Graphical Abstract

Open image in new window

     

Phase Equilibria in the Sodium-Acetate–Sodium-Formate–Water System at Temperatures of from 0 to–22°C and the Anti-icing Properties of Compositions Based on These Salts

Phase equilibria in sections of the phase diagram of the sodium-acetate—sodium-formate–water ternary system with component ratios of NaCH₃COO : NaHCOO varying from 3 : 1 to 1 : 3 are studied, and the anti-icing properties of the compositions based on these salts are investigated. Polythermal sections of ice crystallization and the ice-melting ability for each of the prepared compositions are calculated from the experimental data. The formulation with a 1 : 1 ratio of the considered salts has a eutectic temperature of?22°C, which is 4–6°C lower than the eutectic temperatures of systems based on the individual salts. This formulation displays a high ice-melting ability and can be recommended for use as a de-icer in airports.     

Nanostructured β-Cyclodextrin-Hyperbranched Polyethyleneimine (β-CD-HPEI) Embedded in Polysulfone Membrane for the Removal of Humic Acid from Water

The synthesis of a new β-cyclodextrin-hyperbranched polyethyleneimine (β-CD-HPEI)/polysulfone (PSf) membranes via interfacial polymerization of trimesoyl chloride and β-CD-HPEI is described in this paper. The membranes were characterized by atomic force microscopy (AFM), high resolution scanning electron microscopy (HR-SEM) and contact-angle measurements. Water permeability and rejection data were obtained using a cross-flow filtration system at 0.69 MPa. The membranes were hydrophilic (25° to 63°), showed high humic acid rejection (>80%), and maintained a constant flux throughout the filtration. The modified membranes were rougher than the pristine PSf membranes but they exhibited better antifouling properties due to the hydrophilic surface which acted as a barrier against humic acid deposition. The modification of PSf with β-CD-HPEI resulted in enhanced hydrophilicity and water permeability while still maintaining high humic acid rejection. Supplemental materials are available for this article. Go to the publisher's online edition of Separation Science & Technology to view the supplemental file.     

M1 to M2 Phase Transformation and Phase Cooperation in Bulk Mixed Metal Mo–V–M–O (M=Te, Nb) Catalysts for Selective Ammoxidation of Propane

In the present study we systematically explored hydrothermal synthesis of bulk mixed metal Mo–V–(Te–Nb)–O catalysts and investigated the bulk characteristics of the resulting M1 and M2 phases as well as their roles in the selective ammoxidation of propane. It was found that unlike Mo–V–Te–Nb–O M1 phases, the Mo–V–Te–O M1 phases may be quantitatively transformed into M2 phases of the same chemical composition indicating that Nb stabilizes the M1 structure. The stabilizing role of Nb and Te was further observed in high resolution TEM studies of Mo–V–(Te–Nb)–O catalysts which indicated that structural order and the M1 phase domain size progressively decreased in this order: Mo–V–Te–Nb–O > Mo–V–Te–O > Mo–V–O. The cooperation between the M1 and M2 phases in propane ammoxidation to acrylonitrile was observed only at low propane conversions suggesting that the M1 phase is the only crystalline phase required for the activity and selectivity of the Mo–V–Te–Nb–O catalysts in propane ammoxidation to acrylonitrile at practical propane conversions.