Amidoxime Adsorbent Research Articles

Simple and convenient preconcentration procedure for the isotopic analysis of uranium in seawater.

The demand for monitoring anthropogenic U isotopes, 236U and 233U, in seawater will continue to increase due to radioecological issues and the need for tools for environmental dynamics research. In response to this growing demand, herein, a novel and simple method was developed for the collection of U isotopes in seawater, both in the laboratory and field, using a fabric-like amidoxime adsorbent. The results from the adsorption studies showed that the optimum conditions for processing seawater in a glass beaker were as follows: seawater pH 4, amidoxime adsorbent 0.20 mmol per 500 g seawater and an adsorption time of 9 hours. Alternatively, when using a closed polyethylene container in experiments on-board a ship and using the same ratio of adsorbent to seawater as in the beaker experiment in the laboratory, the optimum conditions were as follows: seawater pH 8 and an adsorption time of 24 hours. Under the above-mentioned conditions, more than 95% of the U underwent adsorption in both the beaker and the polyethylene container experiments. In the case of analyte desorption, more than 80% of U in seawater was recovered using 2-3 mol dm-3 HCl or HNO3 as the eluent. Thus, it was concluded that the amidoxime adsorbent can serve as a simple and effective pre-concentration method for the ultra-trace monitoring of U isotopes in seawater.

Mechanism for the seleikctive adsorption of uranium from seawater using carboxymethyl-enhanced polysaccharide-based amidoxime adsorbent

Land-based uranium resources are becoming scarce because of the widespread development and use of nuclear energy. Therefore, to make up for the shortage of uranium resources, a new chitosan/carboxymethyl-β-cyclodextrin/quaternary ammonium salt–functionalized amidoxime carbon adsorbent (CSAOCF) was designed and synthesized for extracting uranium from seawater. Experimental studies show that the adsorption of uranium by CSAOCF is a spontaneous endothermic reaction and chemical adsorption. The theoretical maximum adsorption capacity of uranium can reach 726 mg/g at 308 K and pH = 6. Moreover, the adsorption efficiency and selectivity of CSAOCF for uranium were significantly improved after the introduction of the carboxymethyl group, and the selection and partition coefficient of CSAOCF for uranium and vanadium increased from 16-fold to 30-fold under the same conditions. This indicates that there is a synergistic effect between carboxyl and amidoxime groups, which can promote the adsorption of uranium by CSAOCF. Furthermore, CSAOCF exhibits good oil resistance and can be reused more than five times. Therefore, CSAOCF containing carboxymethyl and amidoxime functional groups can considerably improve the selective adsorption of uranium and has great potential in the extraction of uranium from seawater.

Selective, rapid extraction of uranium from aqueous solution by porous chitosan–phosphorylated chitosan–amidoxime macroporous resin composite and differential charge calculation

Herein, a new porous chitosan–phosphorylated chitosan–amidoxime macroporous resin composite (PCAR) was designed and synthesized for the rapid and selective extraction of uranium resources from aqueous solution. This study showed that PCAR exhibited excellent adsorption toward uranium in a pH range of 5–9. The dynamic adsorption process aligned with the quasi-second-order kinetic model and corresponded to the chemical adsorption process. The maximum adsorption capacity was 561.28 mg·g−1 at pH 6 and 308 K. Mechanism analysis showed that the synergistic effect of the amidoxime group (−(NH2)C=N–OH), PO, and –NH2 on the PCAR surface improved the uranium adsorption performance. The differential charge density indicated that the amidoxime and phosphate groups provide lone-pair electrons for the adsorption of UO22+ and their synergistic effect improves the UO22+ adsorption performance of PCAR. The uranium distribution coefficients of PCAR and CAR are 4.6 and 2.4 times those of vanadium, respectively. These results indicate that phosphorylation can ameliorate the disadvantage of competitive vanadium adsorption of the amidoxime adsorbent. In addition, PCAR exhibits good reusability and stable adsorption capacity after five adsorption–desorption cycles. Hence, PCAR has excellent potential for uranium extraction from aqueous solution.

Branched fibrous amidoxime adsorbent with ultrafast adsorption rate and high amidoxime utilization for uranium extraction from seawater

Branched fibrous amidoxime adsorbent with ultrafast adsorption rate and high amidoxime utilization for uranium extraction from seawater

Synthesis of Amidoxime Adsorbent by Radiation-Induced Grafting of Acrylonitrile/Acrylic Acid on Polyethylene Film and Its Application in Pb Removal.

In the aquatic environment, heavy metals such as lead ions Pb (II) are of particular importance. These are due to Pb (II) being toxic at concentrations over 0.01 mg/L, when taken continuously over an extended length of time. Organs including the heart, gut, and kidneys are seriously harmed by Pb (II) intoxication. The neurological, reproductive, and bone systems are also affected. The removal of Pb (II) from aquatic environments is, therefore, crucial. Low density Polyethylene (LDPE) is grafted by radiation with Acrylonitrile and acrylic acid (PE-g-AN/AAc) for the adsorption of Pb (II). Factors that control the grafting process for optimum conditions, such as the effect of solvents, the air atmosphere, inhibitors, comonomer concentration, and composition and irradiation dose, are studied to obtain a high grafting yield without homopolymer formation and a higher water uptake. The results showed that the addition of 2.5% by wt% ferric chloride salt effectively inhibits homoploymerization of a mixture of 30% methanol and 70% H2O used as a solvent in nitrogen. The highest graft yield obtained was 320% at a 25 kGy radiation dose with an 80/20 monomer composition and 60% comonomer concentration. The resulting composite films were characterized by XRD to analyze the dispersion properties of the material, SEM for the surface morphology, FTIR analysis for the functional groups, TGA, DSC for the thermal stability and elongation, and tensile strength for the mechanical properties. The uptake of Pb (II) from lead nitrate aqueous solution by (PE-g-AN/AAc) was observed under different conditions of the degree of grafting, contact time, metal ion concentration, and pH. The results obtained suggest LDPE-g-p (AN/AAc) as a superabsorbent for the Pb (II) ion’s removal from an aqueous solution.

Rapid recovery of uranium with magnetic-single-molecular amidoxime adsorbent

Highly efficient treatment of uranium contamination is of great importance for the sustainable development of the environment. The recovery of uranium by adsorbents is a feasible strategy for treating uranium contamination. However, due to insufficient exposure of the contact interfaces, currently available adsorbents usually take extremely long time for uranium adsorption. Herein, a magnetic-single-molecular amidoxime adsorbent M−AO−Fc is fabricated for highly efficient recovery of uranium from nuclear wastewater by endowing the amidoximated cyanoferrocene with magnetism. The adsorbent M−AO−Fc shows a maximum uranium adsorption capacity of 510.60 mg/g in uranium solution. In an acidic simulated nuclear wastewater containing a large number of interfering ions, M−AO−Fc also shows a high uranium adsorption capacity of 84.31 mg/g within a short equilibrium time of 60 min. The full dispersion of M−AO−Fc and full exposure of functional groups are the critical reasons for the excellent uranium adsorption performance. Attributing to the magnetism of M−AO−Fc, this adsorbent can be efficiently recovered by magnetic recovery and shows high reusability. This study proves that the magnetic-single-molecule would be a promising adsorbent for uranium recovery and opens up a new direction for designing a uranium adsorbent.

Catalyst: Challenges in development of adsorbents for recovery of uranium from seawater

Sheng Dai is currently a section head of separations and polymer chemistry and a UT-Battelle Corporate Fellow at the Chemical Sciences Division of the Oak Ridge National Laboratory and a professor of chemistry at the University of Tennessee, Knoxville. He served as a national technical director for a US Department of Energy project aimed at recovering uranium from seawater (2010–2016). His current research interests include ionic liquids, porous materials, and their applications for separation sciences and energy storage, as well as catalysis by nanomaterials.

Removal of Cu(II), Pb(II) and Cr(VI) ions from aqueous solution using amidoximated non-woven polyethylene-g-acrylonitrile fabric.

Pre-irradiation method was applied to graft acrylonitrile (AN) onto non-woven polyethylene film. Graft yield reached 130% at 70kGy radiation dose, 60% monomer concentration and 4h reaction time when H2SO4 was used as an additive. The modification of AN grafted films with hydroxyl amine hydrochloride was done for the preparation of amidoxime adsorbent. The constructed adsorbent was characterized using FTIR, DMA and SEM. The amidoxime adsorbent was used for adsorption of Cu(II), Pb(II) and Cr(VI). Adsorption capacity was investigated under different conditions: contact time, pH and initial metal ion concentration. The optimum condition for maximum adsorption was found to be contact time 72h and initial metal concentration 500ppm for all the metal ions studied and pH5.2 for Cu(II), 5.4 for Pb(II), 1.5 for Cr(VI). Kinetic adsorption data was elucidated using pseudo-first-order and pseudo-second-order equations. The equilibrium experimental data of metal adsorption matched Langmuir isotherm model. From the Langmuir equation, the monolayer saturation adsorption capacity (highest adsorption capacity) of the adsorbent was found to be 74.62mg/g for Cu(II), 107mg/g for Pb(II) and 156.25mg/g for Cr(VI). The thermodynamics of metal adsorption was also investigated. Furthermore, desorption and reuse of the adsorbent film was studied. The results suggest that the adsorbent can be effective for adsorption of Cu(II), Pb(II) and Cr(VI).

Preparation of Amidoxime Adsorbent by Radiation Induced Grafting of Acrylonitrile on Polyethylene Film and Its Application in Cr(VI) Removal

Preparation of Amidoxime Adsorbent by Radiation Induced Grafting of Acrylonitrile on Polyethylene Film and Its Application in Cr(VI) Removal

Efficient removal of methyl orange from aqueous solution using amidoxime adsorbent

ABSTRACT The amidoxime adsorbent was prepared by radiation grafting of acrylonitrile on non-woven polyethylene followed by chemical treatment with hydroxyl amine hydrochloride. The prepared amidoxime adsorbent was used for adsorption of methyl orange (MO) from aqueous solution. The effect of different conditions such as contact time, pH and initial metal ion concentration on the adsorption capacity was investigated. Pseudo-first-order and pseudo-second-order equations were used to study the kinetic adsorption data. A Langmuir isotherm model was used to investigate the equilibrium experimental data. The monolayer saturation adsorption capacity of the adsorbent for MO, as determined from the Langmuir equation, was 142 mg/g of the adsorbent. Moreover, desorption and reuse of the adsorbent film showed satisfactory results. Large-scale recycling of the adsorbent will reduce the production cost, and thereby make the practical application of the adsorbent economically feasible. Abbreviations: Acrylonitrile - AN, Polyethylene - PE, Methylene Orange - MO

Nitrogen-Containing Fabric Adsorbents Prepared by Radiation Grafting for Removal of Chromium from Wastewater.

To remove chromium from wastewater effectively, two types of nitrogen-containing fabric adsorbents, having amidoxime ligand groups and quaternary ammonium anion exchange groups, respectively, were prepared by radiation grafting. In brief, the amidoxime adsorbent is obtained by grafting of acrylonitrile (AN)/methacrylic acid (MAA) onto a nonwoven fabric and subsequent amidoximation with hydroxylamine, while the ammonium adsorbent is obtained by grafting of chloromethylstyrene (CMS) followed by quaternization with trimethylamine. The AN/MAA-grafting reaches a high degree of grafting more than 100%, and the resulting amidoxime adsorbent reaches a high amidoxime density of 4.53 mmol/g. On the other hand, the CMS-grafting reaches a much higher degree of grafting above 200%, and the resulting ammonium adsorbent reaches a high ammonium density of 3.51 mmol/g. FTIR/ATR and TGA/DTA are used for the characterization of the grafted fabrics as well as the relevant fabric adsorbents. Furthermore, the chromium removal of the prepared fabric adsorbent is tested in both batch and column modes. It has been confirmed that the chromium removal was largely dependent on the pH of the solution. At pH 5.0, the amidoxime adsorbent shows a high Cr(III) adsorption capacity of 31.68 mg/g, while the ammonium adsorbent shows a much higher Cr(VI) adsorption capacity of 130.65 mg/g.

Upcycling of polypropylene waste by surface modification using radiation-induced grafting

In this work, upcycling of polypropylene waste into amidoxime functionalized polypropylene adsorbent was studied using radiation-induced grafting technique. Polypropylene waste (PPw) was resulted from accelerated thermal ageing of polypropylene (PP). Bulk grafting of acrylonitrile (AN) onto PPw was achieved by simultaneous radiation grafting method using gamma rays. Degree of grafting of AN on PPw is affected by absorbed dose and dose rate. The acrylonitrile groups of grafted PPw were chemically converted into amidoxime functionality. Both the acrylonitrile-grafted PP waste and its amidoxime product were investigated by FTIR, XRD, SEM-EDX and TGA techniques. The prepared amidoxime adsorbent with amidoxime group density of 8.06mmol/g was used for removal of copper ions from aqueous solutions. The effects of various physicochemical conditions such as: solution pH, adsorbent content, initial metal ion concentration and time on adsorption were studied to maximize adsorption of metal ion. Pseudo-first-order, pseudo-second-order and intra-particle diffusion models were applied to study the kinetics of adsorption. Maximum Langmuir adsorption capacity of 208.3mg/g at pH 5.0 with optimum contact time of 120min was observed. Utilization of PP waste and its comparable adsorption capacity with existing radiation grafted polymer-based adsorbents provide a new, cheap and cost effective system.

Use of apple seeds as new source for synthesis of polyacrylonitrile-based adsorbent to remove Pb(II)

Bromoactylated apple seeds (BAS) was used as new source for the synthesis of environmental adsorbent. Apple seeds were modified by bromoacetyl bromide to obtain a macroinitiator for single electron transfer-living radical polymerization (SET-LRP) of acrylonitrile (AN). The amidoxime (AO) adsorbent was prepared by the reaction of the graft copolymer bromoactylated apple seeds (BAS)/polyacrylonitrile (BAS-g-PAN) with hydroxylamine. Amidoxime BAS-g-PAN (AO BAS-g-PAN) was used to remove Pb(II) and the maximum adsorption for Pb(II) was 1.58 mmol/g. AO BAS-g-PAN could also selectively adsorb Pb(II) from binary ion systems in the existence of Ag(I), Ni(II) and Zn(II). This efficient modifying approach provides a new powerful mean toward filling the gap on apple waste as a potential source for controlling heavy metal pollution.

Enhancing Uranium Uptake by Amidoxime Adsorbent in Seawater: An Investigation for Optimum Alkaline Conditioning Parameters

A high-surface-area polyethylene-fiber adsorbent (AF160-2) has been developed at the Oak Ridge National Laboratory by radiation-induced graft polymerization of acrylonitrile and itaconic acid. The grafted nitriles were converted to amidoxime groups by treating with hydroxylamine. The amidoximated adsorbents were then conditioned with potassium hydroxide (KOH) by varying different reaction parameters such as KOH concentration (0.2, 0.44, and 0.6 M), duration (1, 2, and 3 h), and temperature (60, 70, and 80 °C). Adsorbent screening was then performed with simulated seawater solutions containing sodium chloride and sodium bicarbonate, at concentrations found in seawater, and uranium nitrate at a uranium concentration of ∼7–8 ppm and pH 8. Fourier transform infrared spectroscopy and solid-state NMR analyses indicated that a fraction of amidoxime groups was hydrolyzed to carboxylate during KOH conditioning. The uranium adsorption capacity in the simulated seawater screening solution gradually increased with co...

Enhancement of uranium extraction from seawater using chromic-acid-treated amidoxime adsorbent prepared by simultaneous irradiation grafting technique

Enhancement of uranium extraction from seawater using chromic-acid-treated amidoxime adsorbent was studied. Chromic-acid-treated amidoxime fibers were synthesized based on the simultaneous irradiation grafting method at a low temperature. Low-density polyethylene (LDPE) fibers were treated with chromic acid for up to 90 minutes. After the treatment, the fibers were submerged in 60:40 acrylonitrile:methacrylic acid monomer by volume and irradiated with 40 kGy γ-ray. The maximum grafting efficiency of about 90% occurred at 20 minutes of acid treatment time, as a significant enhancement of 30% compared to the literature-reported value of about 70%. When submerged in shallow seawater with an average temperature of 30 °C for 4 weeks, the amidoxime adsorbent exhibited the adsorption capacity of 2.06 g-U/kg-adsorbent, which was 37% higher than the literature-reported value. These significantly increased grafting and adsorption efficiencies were attributed to the increased surface area of chromic-acid-etched LDPE fibers. Moreover, for the submersion up to 8 weeks, the adsorption increased to 2.15 g-U/kg-adsorbent. The adsorption capacity was evaluated to reduce to about 65% after eight cycles of repeated usage. Uranium concentrations in Thailand's seawater collected at various depths and locations were analyzed using inductively coupled plasma-mass spectrometry (ICP-MS) to be about 3 ppb everywhere.

Sweet Potato Starch Residue as Starting Material To Prepare Polyacrylonitrile Adsorbent via SI-SET-LRP

Sweet potato starch residue (SPSR) was used as starting material to prepare an eco-friendly adsorbent. SPSR was modified by bromoacetyl bromide to obtain a macroinitiator for surface-initiated single electron transfer-living radical polymerization (SI-SET-LRP) of acrylonitrile (AN) catalyzed by La(0)/hexamethylenetetramine (HMTA) in N,N-dimethylformamide (DMF) in the presence of ascorbic acid (VC). The amidoxime (AO) adsorbent was prepared by the reaction of the graft copolymer bromoactylated sweet potato starch (BSPS)/polyacrylonitrile (BSPS-g-PAN) with hydroxylamine. The maximum adsorption capacity for Hg(II) was 4.03 mmol·g(-1). This simple method provided a novel approach to recycle and reuse agricultural residues for controlling heavy metal pollution.

Parametric studies on the synthesis of amidoximated adsorbent resins

AbstractThe main goal of this study was to obtain acrylonitrile (AN)‐divinylbenzene (DVB) copolymer beads that can serve as the matrix for preparation of amidoxime resins. AN‐DVB amidoxime resin was synthesized via suspension polymerization and the effect of different parameters such as the speed of stirrer, the amounts of suspending agent, hydrophilic agent, diluent agent, and initiator on its properties was investigated by fractional factorial (Taguchi) experimental design method. This method gives much‐reduced variance for the experiments with optimum control parameters setting and provides a set of minimum experiments compared to the conventional methods. The results showed that the most effective parameters on the amidoximation of resins were hydrophilic agent content, speed of stirrer, and the amount of suspending agent, respectively. Furthermore, anion‐exchange capacity of the amidoxime resins was utilized as a criterion for the evaluation of amidoxime adsorbent groups and the adsorption potential of the synthesized resins was determined by cation‐exchange capacity. The amount of methylacrylate as a hydrophilic agent had the most significant effect on the ion‐exchange capacity of the final product. Swelling ratio was also measured to evaluate the adsorption capacity of the synthesized resin. The results showed that the amounts of hydrophilic and diluent agents had significant effects on swelling ratio of resin. Finally, cation‐exchange capacity and swelling ratio of amidoxime resin were changed greatly because of alkaline treatment, but it had no significant effect on the anion‐exchange capacity of the synthesized resin. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Current status of adsorbent for metal ions with radiation grafting and crosslinking techniques

Removal of toxic metals from streaming water and ground water is important task to preserve environment. Radiation processing of grafting and crosslinking can synthesis adsorbent having high performances. Graft adsorbent can be synthesized by using the conventional polymer like polyethylene having variety shapes such as membrane, cloth, and fiber. Especially, the obtained fibrous adsorbent has 100 times higher rate of adsorption than that of commercialized resin. Fibrous adsorbent of iminodiacetate was applied to the removal of cadmium from the scallop waste. Furthermore, the amidoxime adsorbent is useful for recovery of rare metals such as uranium and vanadium in seawater. Novel fibrous adsorption for arsenic was synthesized by direct grafting of phosphoric monomer and following zirconium-loading. Crosslinked natural polymers like carboxymethyl chitin–chitosan in the paste-like state are applicable for the metal adsorbent. This adsorbent can be biodegraded after usage.

Fine Fibrous Amidoxime Adsorbent Synthesized by Grafting and Uranium Adsorption–Elution Cyclic Test with Seawater

Fibrous amidoxime adsorbents were prepared by radiation‐induced co‐grafting of acrylonitrile (AN) and methacrylic acid (MAA) and subsequent amidoximation. Adsorption of uranium in seawater was evaluated by pumping seawater into the adsorbent column. The best monomer ratio of AN and MAA was 7:3 for continual usage of uranium adsorption. Though hydrochloric acid is an effective eluting agent for the metals adsorbed on the adsorbent, amidoxime groups were simultaneously damaged after five cycles of adsorption–desorption. This deterioration was reduced by an alkaline treatment of the adsorbents after each elution. Furthermore, various organic acids were examined as elution agents. It was found that the 80% of adsorption activity was still maintained after five cycles of adsorption–desorption when tartaric acid was used for eluting agent.

Recovery of cadmium from waste of scallop processing with amidoxime adsorbent synthesized by graft-polymerization

Fabric adsorbent having amidoxime function was synthesized by radiation-induced graft-polymerization. This adsorbent was applied to the removal of Cd from the scallop waste. The scallop waste was homogenized as a pre-treatment. The obtained top layer was used for the Cd absorption experiment at various pH conditions. At pH 6, the adsorbent showed the highest performance in Cd adsorption. The concentration factor was thousand for Cd. Preliminary column experiment was also carried out. The amidoxime adsorbent recovered 96.1% of Cd in the waste solution.