Amidoxime Groups Research Articles

Amidoxime surface modification of polyindole nanofiber membrane for effective removal of Cr(VI) from aqueous solution

Surface amidoxime-modified polyindole (SAMPI) nanofiber membrane was prepared by a facile method using electrospun poly(5-cyanoindole) nanofibers treated by hydroxylamine for removal of hexavalent chromium (Cr(VI)) from aqueous solution. FTIR and XPS results confirm the presence of amidoxime groups on the surface of SAMPI nanofiber membrane. The SAMPI nanofiber membrane shows higher hydrophilicity which can favor the Cr(VI) adsorption. The maximum adsorption capacities (Q m ) calculated from Langmuir model are 340.14, 380.23 and 404.86 mg/g at 25, 35 and 45 °C, respectively. The adsorption equilibrium can be reached in the range of 20–30 min with initial solution concentration increasing from 100 to 200 mg/L, and the adsorption process can be better described using pseudo-second-order model than pseudo-first-order and intraparticle diffusion model. The isotherm data fit better to Langmuir model than Freundlich, Temkin and D–R isotherm models. The adsorption capacity can remain 81% after 10 cycle’s usage, and the flux and rejection rate can keep about 84 and 86% after 5 cycle’s usage, which show good durability performance. All these results indicate that the SAMPI nanofiber membrane might have potential applications in wastewater treatment for removal of Cr(VI).

Synthesis and characterization of magnetic amidoximated chitosan-g poly(polyacrylonitrile)/laponite RD nanocomposites with enhanced adsorption capacity for Cu$^{2+}$

Magnetic amidoximated nanocomposites based on a combination of chitosan and magnetic laponite RD were prepared and examined for the removal of Cu$^{2+}$ from aqueous solutions. Magnetic laponite RD was prepared by an in situ method. In order to prepare magnetic amidoximated nanocomposites, acrylonitrile was grafted to chitosan in the presence of magnetic laponite RD. Then the nitrile pendants on magnetic chitosan-g-polyacrylonitrile/laponite RD (mChtioPANLap) were converted to amidoxime groups. We developed a polyamidoximated magnetic nanocomposite based on a mixture of chitosan/laponite RD, possessing a high adsorption capacity for Cu$^{2+}$. By introducing magnetic laponite RD the adsorption capacity of nanocomposites for Cu$^{2+}$ was significantly improved. The effects of contact time, initial concentration of Cu$^{2+}$, initial pH of Cu$^{2+}$ solutions, and temperature on adsorption process were investigated. Studying adsorption kinetics showed that the experimental data are described better by the pseudo-second-order kinetic model. The adsorption of Cu$^{2+}$ on nanocomposites followed the Langmuir isotherm model well. Additionally, the fitting of isotherm data by the Dubinin-Radushkevich model showed that the adsorption process occurred by physisorption mechanism. The thermodynamic data indicated that the adsorption process was spontaneous and endothermic.

Amidoxime-functionalized nanocrystalline cellulose–mesoporous silica composites for carbon dioxide sorption at ambient and elevated temperatures

Nanocrystalline cellulose–mesoporous silica composites with attached double amidoxime groups show high CO2sorption at elevated temperatures.

Maghemite nanoparticles bearing di(amidoxime) groups for the extraction of uranium from wastewaters

Polyamidoximes (pAMD) are known to have strong affinities for uranyl cations. Grafting pAMD onto the surface of functionalized maghemite nanoparticles (MNP) leads to a nanomaterial with high capacities in the extraction of uranium from wastewaters by magnetic sedimentation. A diamidoxime (dAMD) specifically synthesized for this purpose showed a strong affinity for uranyl: Ka = 105 M-1 as determined by Isothermal Titration Calorimetry (nano-ITC). The dAMD was grafted onto the surface of MNP and the obtained sorbent (MNP-dAMD) was characterized. The nanohybrids were afterward incubated with different concentrations of uranyl and the solid phase recovered by magnetic separation. This latter was characterized by zeta-potential measurements, X-Ray Photoelectron Spectroscopy (XPS) and X-Ray Fluorescence spectroscopy (XRF), whereas the supernatant was analyzed by Inductively Coupled Plasma coupled to Mass Spectrometry (ICP-MS). All the data fitted the models of Langmuir, Freundlich and Temkin isotherms very well. These isotherms allowed us to evaluate the efficiency of the adsorption of uranium by MNP-dAMD. The saturation sorption capacity (qmax) was determined. It indicates that MNP-dAMD is able to extract up to 120 mg of uranium per gram of sorbent. Spherical aberration (Cs)-corrected High-Resolution Scanning Transmission Electron Microscopy (HRSTEM) confirmed these results and clearly showed that uranium is confined at the surface of the sorbent. Thus, MNP-dAMD presents a strong potential for the extraction of uranium from wastewaters.

An Amidoximated-UHMEPE Fiber for Selective and High Efficient Removal of Uranyl and Thorium from Acid Aqueous Solution

High efficient removal and recovery of uranium and thorium from nuclear waste solution are essential for environmental preservation and fuel recycle. A new polymer fiber adsorbent (UHMEPE-g-PAO fiber), prepared by amidoximation of grafted polyacrylonitrile onto Ultra High Molecular Weight Polyethylene (UHMWPE) fiber, was used to remove the uranyl and thorium ions from acid aqueous solutions and its performance was carefully investigated. It was found that uranyl ion can penetrate the fiber through the connected pore structures, forming (UO2) (R-C(NH2)-NO)2 chelates with the amidoxime groups within the fiber. Two amidoxime groups (U-N and U-Oeq) and two water molecules (U-Oeq2) are bound to uranyl ion in the fiber. On the contrary, thorium ions are adsorbed mainly on the fiber surface in the form of Th(OH)4 precipitate that blocks the entrance of Th4+ ion into fiber pores. The maximum included other two capacities of uranyl and thorium ions were estimated to be 262.01 mg/g and 160 mg/g at room temperature with pH 3.0, respectively. The results also indicate that the UHMWPE-g-PAO fiber has higher adsorption selectivity for uranyl ion than thorium ion. Uranium and thorium oxide particles were obtained as the ultimate product after sintering of the fiber adsorbent. This novel and environmentally friendly adsorption process is feasible to extract uranium or thorium from acidic aqueous solution.

Preparation of hollow SiO2 microspheres functionalized with amidoxime groups for highly efficient adsorption of U(VI) from aqueous solution

The amidoxime-functionalized hollow SiO2 microspheres (HSA) were prepared for highly efficient U(VI) adsorption. Results showed that amidoxime modification could improve both sorption capacity and sorption selectivity for U(VI), however, excess functionalization might block the mesopores and thus restricting U(VI) sorption. The maximum U(VI) sorption capacity was 109.6 mg/g for HSA15 at 298 K and pH 5.0. The U(VI) sorption isotherms could be described by Langmuir model; whereas the sorption kinetics fitted well with the pseudo-second-order equation, indicating of monolayer chemisorption mechanism. The HSA sorbents could be efficiently regenerated by 0.6 M HNO3 and reused for several sorption–desorption cycles.

Unprecedented stereoselective synthesis of 3-methylisoxazolidine-5-aryl-1,2,4-oxadiazoles via 1,3-dipolar cycloaddition and study of their in vitro antioxidant activity

ABSTRACTThe stereoselective 1,3-dipolar cycloaddition between allyl cyanide and a menthone-derived nitrone led to the desired isoxazolidine in good yield. Once the nitrile group transformed to an amidoxime group, the cyclocondensation of various aldehydes with chiral amidoxime led to unprecedented enantiopure 3-methylisoxazolidine-5-aryl-1,2,4-oxadiazoles. The menthone chiral auxiliary was then removed with acid hydrolysis. The new compounds were also screened for their in vitro antioxidant activity using DPPH and FRAP assays. Some of the compounds showed promising antioxidant activity.

Preparation of Amidoxime-Based Nylon-66 Fibers for Removing Uranium from Low-Concentration Aqueous Solutions and Simulated Nuclear Industry Effluents

Amidoximated nylon-66 fiber containing double amidoxime groups per repeating unit (coded as PA66-g-PGMA-IDPAO) for the purpose of removing low uranium concentrations (1–25 mg/L) from aqueous solutions and application in simulated nuclear industry effluents was prepared by a simultaneous radiation-induced emulsion graft polymerization method. It was characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, and single fiber tensile strength tester. Batch adsorption experiments were conducted to investigate the effect of initial pH, sorption isotherm, adsorption kinetics, and thermodynamics. It was found that the optimum initial pH is 5.0. The sorption isotherm followed the Langmuir isotherm. The adsorption kinetics fit the pseudo-second-order model. The thermodynamics parameters revealed that the adsorption process was spontaneous and endothermic. The sorption test performed in a simulated nuclear industry effluent demonstrated a high adsorption effi...

Facile regeneration and modification of industrial used chelating resin for fuel oil desulfurization

A systematic study was carried out on the preparation and application of metal-loaded polypropylene-divinyl benzene resin for dibenzothiophene adsorption. Amidoxime groups over used industrial polypropylene-divinyl benzene chelating resin were regenerated through a chemical graft reaction, and the highest regeneration efficiency of about 90 % can be reached. Different metal phases (Zn, Ni, Cu, Fe, Bi, and Ag) were introduced to the regenerated resin via an incipient-wetness impregnation method to examine their desulfurization efficiency. The desulfurization efficiency of ca. 86.3 % can be gained over Zn-loaded resin (Zn-R) under optimized reaction conditions. The order of different desulfurization influencing factors was further verified according to the orthogonal experiments, that is, desulfurization temperature > metal loading content > space velocity > organic sulfur concentration. Distribution of adsorption products was analyzed, and the results reveal that the metal-modified resins can effectively remove the organic sulfur compounds in diesel oil without loss of its octane value. The desulfurization effect of metal-contained resins is primary determined by the π-complexation.

Iron phthalocyanine supported on amidoximated PAN fiber as effective catalyst for controllable hydrogen peroxide activation in oxidizing organic dyes

Iron(II) phthalocyanine was immobilized onto amidoximated polyacrylonitrile fiber to construct a bioinspired catalytic system for oxidizing organic dyes by H2O2 activation. The amidoxime groups greatly helped to anchor Iron(II) phthalocyanine molecules onto the fiber through coordination interaction, which has been confirmed by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and UV⿿vis diffuse reflectance spectroscopy analyses. Electron spin resonance studies indicate that the catalytic process of physically anchored Iron(II) phthalocyanine performed via a hydroxyl radical pathway, while the catalyst bonded Iron(II) phthalocyanine through coordination effect could selectively catalyze the H2O2 decomposition to generate high-valent iron-oxo species. This may result from the amidoxime groups functioning as the axial fifth ligands to favor the heterolytic cleavage of the peroxide OO bond. This feature also enables the catalyst to only degrade the dyes adjacent to the catalytic active centers and enhances the efficient utilization of H2O2. In addition, this catalyst could effectively catalyze the mineralization of organic dyes and can be easily recycled without any loss of activity.

Preparation of amidoximated coaxial electrospun nanofibers for uranyl uptake and their electrochemical properties

Abstract In this work, the core-shell nanofibers of polyacrylonitrile@polystyrene (PS@PAN) with PS as core and PAN as shell were prepared initially via coelectrospinning technique. The cyano groups of PAN shell were converted into amidoxime groups to obtain surface active PS@PAN-oxime via subsequent amidoximation process. The surface morphologies, compositions and amidoximation of the coaxial nanofibers based on PS@PAN were determined by scanning electron microscope (SEM), transmission electron microscope (TEM), Fourier transform infrared spectra (FT-IR) and X-ray photoelectron spectroscopy (XPS). The proposed PS@PAN-oxime nanofibrous mats were used as absorbents for uranyl ions in aqueous solutions. The absorption mechanism and performance were investigated by electrochemical measurements. Furthermore, the quantitative measurement of uranium adsorption on nanofibers was firstly achieved by differential pulse voltammetry (DPV). The analysis of absorption experimental data revealed that uranyl ions on PS@PAN-oxime coaxial nanofibers followed pseudo-second-order model and the Langmuir isotherm. The effect of interferences with potential metal ions was examined and the recovery studies in lake water samples were also conducted. The adsorption capacity of the uranyl ions could reach 127 mg U/g.

Mesoporous Alumina with Amidoxime Groups for CO2 Sorption at Ambient and Elevated Temperatures

Development of various mesostructures with introduced basic species such as amine groups represents a viable strategy for enhancing adsorption of acidic molecules such as CO2. To follow this strategy, mesoporous alumina-based materials with incorporated amidoxime functionality were prepared by evaporation induced self-assembly of commercial boehmite nanoparticles as an alumina precursor, (3-cyanopropyl)triethoxysilane as an organosilica precursor, and Pluronic P123 triblock copolymer as a soft template under acidic conditions. In the next synthesis step, the resulting mesoporous materials with cyanopropyl groups were subjected to hydrothermal reaction with hydroxylamine hydrochloride at slightly basic conditions and 80 °C to convert cyanopropyl groups to amidoxime functionalities. The latter sorbents showed fairly high CO2 uptake at ambient conditions (25 °C, 1.2 atm) and remarkably high sorption capacity (3.84 mmol/g) at 120 °C. Good thermal and chemical stabilities of these materials combined with high ...

The applications of populus fiber in removal of Cr(VI) from aqueous solution

The surface modification of natural materials to be applied in removal of Cr(VI) from aqueous solutions has attracted much attention. A natural sorbent for Cr(VI) based on natural populus fibers (PF) is prepared by transforming the cyano groups (AN) in polyacrylonitriles (PAN) grafted from PF into amidoxime groups (AO), which has strong ability to attract and chelate heavy metal ions. The prepared sorbent is characterized by Fourier Transform Infrared Spectra (FT-IR), thermogravimetric analysis (TGA), solid-state nuclear magnetic resonance (13C NMR) and scanning electron microscope (SEM). As potassium dichromate solution (K2Cr2O7) is used as a target solution for detecting adsorption capacity of the sorbent, the adsorption kinetics of the sorbent for chromiun is consistent with the pseudo-second-order kinetic model by analyzing the adsorption amount as a function of the sorbent dispersed duration in solution at pH=2. The expected adsorption mechanism is that the Cr(VI) in anionic ions Cr2O72− and HCrO4− are adsorbed through electrostatic attraction but when Cr(VI) is reduced to Cr(III) by AO, the electronegative nitrogen and oxygen in AO chelate it through coordination bond. The as-prepared PF derivant with high adsorption efficiency of chromium 180.5mg/g (3.47mmol/g), low cost, reusability and greenly preparation process suggests that the development of natural PF as a sorbent in removal of Cr(VI) from aqueous solutions is a destined significant approach.

A Conductive Copolymer Based on Graphene Oxide and Poly (amidoxime-pyrrole) for Adsorption of Uranium (VI)

A novel conducting copolymer based on amidoxime groups, polypyrrole and graphene oxide was synthesized by in situ copolymerization by usin g two monomers. The monomer, amidoxime-pyrrole, was synthesized by amidoximation of 1-(2-cyanoethyl) pyrrole. The other monomer, GO-pyrrole, was prepared via esterification between –COOH of GO and –NH2 of 1-(3-aminopropyl) pyrrole. The conductive ability of the copolymer was based on conductive [Formula: see text]-conjugated system of polypyrrole backbone. The copolymer was able to be used as an effective sorption material for the preconcentration and recovery of uranium. The maximum of adsorption capacity for uranyl ion is as high as 149.57[Formula: see text]mg/g.

Introduction of double amidoxime group by double post surface modification on poly(vinylbenzyl chloride) beads for higher amounts of organic dyes, As (V) and Cr (VI) removal

In this study, the synthesis of micron-sized poly(vinylbenzyl chloride) (p(VBC)) beads and subsequent conversion of the reactive chloromethyl groups to double amidoxime group containing moieties by post modification is reported. The prepared beads were characterized by SEM and FT-IR spectroscopy. The amidoximated p(VBC) beads were used as adsorbent for the removal of organic dyes, such as eosin y (EY) and methyl orange (MO), and heavy metals containing complex ions such as dichromate (Cr2O72−) and arsenate (HAsO42−) from aqueous media. The effect of the adsorbent dose on the percent removal, the effect of initial concentration of adsorbates on the adsorption rate and their amounts were also investigated. The Langmuir, Freundlich and Temkin adsorption isotherms were applied to the adsorption processes. The results indicated that the adsorption of both dichromate and arsenate ions obeyed the Langmuir adsorption model. Interestingly, it was found that the prepared beads were capable of removing significant amounts of arsenate and dichromate ions from tap and river (Sarıcay, Canakkale–Turkey) water.

Preparation of corn stalk-based adsorbents and their specific application in metal ions adsorption

AbstractCorn stalk-based adsorbents modified from corn stalk were prepared by Cu(0)-mediated reversible-deactivation radical polymerization (Cu(0)-mediated RDRP). They were applied to remove metal ions and they exhibited good adsorption capacity, especially for Hg(II). Adsorption properties of corn stalk can be enhanced by introducing cyano, amino, amidoxime, and carboxyl groups onto its surface, which results in efficient adsorbents for different metal ions. TGA, SEM, EA, and FTIR analyses were employed to characterize the structures of corn stalk-

Bifunctional Ion-Conducting Polymer Electrolyte for the Vanadium Redox Flow Battery with High Selectivity

The need for electrochemical energy storage increases along with the growing share of fluctuating renewables for power generation. The all-vanadium redox flow battery (VRB) has experienced increasing attention in this context. Its electrolyte membrane is a key component, yet currently perfluorinated materials (e.g., Nafion) are mainly used in VRBs, which have neither been designed for this particular application, nor are they cost-effective. The cross-over of redox active vanadium species impairs cell efficiency, in particular in case of thin Nafion membranes with low ohmic resistance. Here, we present a potentially generic concept of a bifunctional ion-conducting membrane prepared by radiation grafting with sulfonic acid proton exchange sites and amidoxime moieties. The crossover of vanadium-ions is reduced four-fold in the presence of amidoxime groups without markedly impairing the conductivity of the membrane. A VRB cell containing such membrane shows increased energy efficiency and negligible capacity fading over 122 charge / discharge cycles compared to cells with Nafion membrane, which showed a loss of discharge capacity of around 35% after 35 cycles and considerable electrolyte imbalance.

MCM-41 silica particles grafted with polyacrylonitrile: Modification in to amidoxime and carboxyl groups for enhanced uranium removal from aqueous medium

The uranium ion adsorption on the pristine MCM-41, amidoxime (AMD) and carboxyl (CA) groups modified particles was studied. The amounts of adsorbed U(VI) ions onto the pristine MCM-41, CA and AMD modified MCM-41 particles were found to be 58.9, 296.7 and 442.3 mg/g, respectively. The experimental equilibrium data was found to fit the Langmuir model well for all the tested adsorbents. The pristine, CA and AMD modified particles can be regenerated using 10 mM HNO3 solution with more than 95% recovery. Hence, AMD and CA modified particles are stable, and easily regenerated. Particularly, AMD modified MCM-41 particles with high adsorption capacity seems to be a promising adsorbent for removal of U(VI) ions from aqueous solutions.

Hg(II) adsorption using amidoximated porous acrylonitrile/itaconic copolymers prepared by suspended emulsion polymerization.

Initially, porous acrylonitrile/itaconic acid copolymers (AN/IA) were prepared by suspended emulsion polymerization. Successively, the cyano groups in AN/IA copolymers were converted to amidoxime (AO) groups by the reaction with hydroxylamine hydrochloride. The structures of the AN/IA and amidoximated AN/IA (AO AN/IA) were characterized by infrared spectroscopy, scanning electron microscopy, and porous structural analysis. The adsorption properties of AO AN/IA for Hg(II) were investigated. The results show that AO AN/IA has mesopores and macropores, and surface area of 11.71 m(2) g(-1). It was found that AO AN/IA has higher affinity for Hg(II), with the maximum adsorption capacity of 84.25 mg g(-1). The AO AN/IA also can effectively remove Hg(II) from different binary metal ion mixture systems. Furthermore, the adsorption kinetics and thermodynamics were studied in detail. The adsorption equilibrium can quickly be achieved in 4 h determined by an adsorption kinetics study. The adsorption process is found to belong to the second-order model, and can be described by the Freundlich model.

Radiation synthesis of a new amidoximated UHMWPE fibrous adsorbent with high adsorption selectivity for uranium over vanadium in simulated seawater

A new kind of highly efficient adsorbent material has been fabricated in this study for the purpose of extracting uranium from seawater. Ultra-high molecular weight polyethylene (UHMWPE) fiber was used as a trunk material for the adsorbent, which was prepared by a series of modification reactions, as follows: (1) grafting of glycidyl methacrylate (GMA) and methyl acrylate (MA) onto UHMWPE fibers via Co-60 gamma-ray pre-irradiation; (2) aminolyzation of UHMWPE fiber by the ring-opening reaction between of epoxy groups PGMA and ethylene diamine (EDA); (3) Michael addition of amino groups with acrylonitrile (AN) to yield nitrile groups; (4) amidoximation of the attached nitrile moieties by hydroxylamine in dimethyl sulfoxide-water mixture. Modified UHMWPE fibers were characterized by means of attenuated total reflectance-Fourier transformed infrared spectroscopy (ATR-FTIR), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) to confirm the attachment of amidoxime (AO) groups onto the UHMWPE fibers. The results of X-ray diffraction (XRD) and single fiber tensile strength verified that the modified UHMWPE fiber retained excellent mechanical properties at a low absorbed radiation dose. The adsorption performance of the UHMWPE fibrous adsorbent was evaluated by subjecting it to an adsorption test in simulated seawater using a continuous-flow mode. The amount of uranium adsorbed by this AO-based UHMWPE fibrous adsorbent was 1.97 mg-U/g after 42 days. This new adsorbent also showed high selectivity for the uranyl ion, and its selectivity for metal ions was found to decrease in the following order: U > Cu > Fe > Ca > Mg > Ni > Zn > Pb > V > Co. The adsorption selectivity for uranium is significantly higher than that for vanadium. In addition, preparation of this modified adsorbent consumes much smaller amounts of the toxic acrylonitrile monomer than the conventional preparation methods of AO-based polyethylene fibers. (C) 2016 Published by Elsevier Ltd.