Properties and evaluation of amidoxime-based UHMWPE fibrous adsorbent for extraction of uranium from seawater

An amidoxime-based ultra-high molecular weight polyethylene (UHMWPE) fibrous adsorbent was successfully prepared by γ-irradiation-induced graft copolymerization of acrylonitrile (AN) and acrylic acid (AA), followed by amidoximation. The grafting of AN and AA on the UHMWPE fiber and the amidoximation of the grafted fiber were confirmed by Fourier transform infrared spectroscopy, scanning electron microscopy, and thermogravimetric analysis. The mechanical property of the original and modified UHMWPE fibers was compared by single-filament strength test. The adsorption property of the UHMWPE fibrous adsorbent was evaluated by adsorption test in uranyl nitrate solution and seawater. The surface of the modified UHMWPE fibers was covered by the grafting layer and became rough. The tensile strength of the amidoxime-based UHMWPE fibrous adsorbent was influenced by the absorbed dose and hydrochloric acid elution, but was independent of the grafting yield and amidoximation. The uranium adsorption amount of the amidoxime-based UHMWPE fibrous adsorbent after immersing in seawater for 42 days was 2.3 mg-U/g.     

Poly(amidoxime)-reduced graphene oxide composites as adsorbents for the enrichment of uranium from seawater

The development of efficient materials for high extraction of uranium(UO22+) from seawater is critical for nuclear energy. Poly(amidoxime)-reduced graphene oxide(PAO/rGO) composites with excellent adsorption capability for UO22+ were synthesized by in situ polymerization of acrylonitrile monomers on GO surfaces, followed by amidoximation treatment with hydroxylamine. The adsorption capacities of PAO/rGO composites for UO22+ reached as high as 872 mg/g at pH 4.0. The excellent tolerance of these composites for high salinity and their regeneration-reuse properties can be applied in the nuclear-fuel industry by high extraction of trace UO22+ ions from seawater.     

Diethylenetriamine functionalized silica gel for adsorption of uranium from aqueous solution and seawater

Journal of Radioanalytical and Nuclear Chemistry - The diethylenetriamine (DETA) organic moiety was anchored covalently on the surface of silica gel to obtain a surface-modified adsorbent...     

Poly(amidoxime) functionalized MoS2 for efficient adsorption of uranium(VI) in aqueous solutions

Journal of Radioanalytical and Nuclear Chemistry - A novel adsorbent for enrichment of trace uranium (U(VI)) ions in aqueous solution is designed based on the excellent adsorption capacity of...     

Application of poly(amidoxime)/scrap facemasks in extraction of uranium from seawater: from dangerous waste to nuclear power

Journal of Radioanalytical and Nuclear Chemistry - To effectively kill microorganisms on scrap facemasks (FMs) surface and provide new material for extracting uranium (U(VI)) from seawater, scrap...     

Optimization of layered double hydroxide stability and adsorption capacity for anionic surfactants

Low cost adsorption technology offers high potential to clean up laundry rinsing water. From an earlier selection of adsorbents (Schouten et al. 2007), layered double hydroxide (LDH) proved to be an interesting material for the removal of anionic surfactant, linear alkyl benzene sulfonate (LAS) which is the main contaminant in rinsing water. The main research question was to identify the effect of process parameters of the LDH synthesis on the stability of the LDH structure and the adsorption capacity of LAS. LDH was synthesized with the co-precipitation method of Reichle (1986); a solution of M²⁺(NO₃)₂ and M³⁺(NO₃)₃ and a second solution of NaOH and Na₂CO₃ were pumped in a beaker and mixed. The precipitate that was formed was allowed to age and was subsequently washed, dried and calcined. The process parameters that were investigated are the concentration of the initial solutions, M²⁺/M³⁺ ratio and type of cations. The crystallinity can be improved by decreasing the concentration of the initial solutions; this also decreases the leaching of M³⁺ from the brucite-like structure into the water. The highest adsorption capacity is obtained for Mg²⁺/Al³⁺ with a ratio 1 and 2 because of the higher charge density compared to ratio 3. Storing the LDH samples in water resulted in a reduction of adsorption capacity and a decrease in surface area and pore volume. Therefore, LDH is not applicable in a small device for long term use in aqueous surroundings. The adsorption capacity can be maintained during storage in a dry N₂ atmosphere.     

Carbon dioxide and nitrogen adsorption on porous copolymers of divinylbenzene and acrylic acid

Porous copolymers of divinylbenzene (DVB) and acrylic acid (AA) having DVB:AA ratios of 6:4, 8:2 and 9:1 were prepared following a distillation-precipitation method, using toluene as the porogenic agent. The materials thus obtained, which showed specific surface area in the range of 380–600 m² g^?1 and pore volume in the range of 0.14–0.18 cm³ g^?1, were investigated as possible adsorbents for CO₂ capture from the flue gas of coal-fired power stations. For that purpose, the isosteric heat of adsorption (and CO₂ adsorption capacity) was analysed from N₂ and CO₂ adsorption equilibrium isotherms obtained over a temperature range. For CO₂, q _st resulted to be in the range of 27–31 kJ mol^?1 (the highest value corresponding to the 6:4 sample), while for N₂ a value of q _st ≈ 12 kJ mol^?1 was obtained. Equilibrium adsorption capacity for CO₂ (at ambient temperature and pressure) showed the value of about 1.35 mmol g^?1. These results are discussed in the broader context of corresponding literature data for CO₂ capture using protonic zeolites.     

Changes in the properties of HDPE fibers upon radiation grafting with acrylic acid

The morphology and the physical and mechanical properties of graft-modified polyethylene fibers have been studied. Two types of fibers, with the diameters of 10 μm (1.1 dtex) and 40 μm (7.5 dtex), were modified by radiation-induced grafting with acrylic acid. The extent of grafting was determined gravimetrically. Confirmation of gravimetrically obtained values was achieved using conductometric titration. The fibers were hydrated at pH 2 and pH 7. The degree of swelling was 120% at pH 2 and 200% at pH 7. The transversal distribution of polyacrylic acid in the fibers was determined. Fibers were stained and observed with an optical microscope. The diffusion of the monomer into the bulk was found to be rather fast. The changes in the total crystalline content and the lamellar thickness distributions in consequence of irradiation and grafting were determined by differential scanning calorimetry analysis. The measurements showed no effects of irradiation on the crystallinity in either type of fiber, whereas a decreasing crystallinity caused by grafting was noticed in the 40 μm fibers. The lamellar thickness distributions narrowed upon irradiation, indicating recrystallization as a result of chain scission. Wide angle x-ray scattering and Raman analysis of dry and hydrated fibers were conducted to study the behavior of the fibers in an aqueous environment. These results both showed a decreasing crystalline content caused by fiber hydration. Tensile tests were carried out to evaluate how grafting, hydration and Ca²⁺-crosslinking of grafts affected the fiber strength. Grafting and Ca²⁺-crosslinking, as well as hydration, resulted in a decreasing E-modulus for the 40 μm fibers, whereas no significant change could be noticed in the 10 μm fibers. © 1995 John Wiley & Sons, Inc.     

Optimization of conditions for grafting acrylic acid to polyethylene terephthalate by radiation

The swelling behaviour of polyethylene terephthalate (PET) film in different media has been examined; the γ-ray induced graft copolymerization to PET of acrylic acid in these media has also been investigated. The influence of film thickness and crystallinity as well as the nature of the swelling agent are discussed with reference to the resultant degrees of equilibrium swelling and grafting. Aqueous dichloracetic acid is a suitable swelling agent for grafting to crystalline PET; methanol is adequate, but less efficient, for grafting to amorphous PET. Swelling and grafting in the case of PET fabric are complicated by dissolution and physical disintegration, respectively. However, grafting to a fairly low extent can be accomplished in dilute aqueous dichloracetic acid.     

Determination of uranium in seawater samples by liquid chromatography using mandelic acid as a complexing agent

The determination of uranium at different stages of the recovery process as well as in seawater is important in its recovery study. A previous study developed a high-performance liquid chromatography (HPLC) method for uranium determination in seawater using α-hydroxy isobutyric acid as a chelating agent. However, this method causes turbidity in process samples containing high amounts of iron, resulting in the clogging of the HPLC column. In the present work, use of mandelic acid as a chelating agent for uranium has been explored. Elution conditions were optimized for the separation of iron [Fe(III)] and uranium [U(VI)] by studying the effect of an ion interaction reagent, the concentration of mandelic acid, and methanol content in the mobile phase. Different parameters were optimized to develop off- line pre-concentration of uranyl-mandelate on the reversed stationary phase. The method offers quantitative recovery of uranium and linearity in the U(VI) concentration range of 0.5 ppb to 500 ppb and can be used for the determination of U(VI) in process samples with Fe/U amount ratios up to 3,000. The method has been successfully used for the determination of U(VI) in seawater samples and process samples. The developed methodology was validated by comparing the results with those of isotope dilution-thermal ionization mass spectrometry.     

Non-isothermal crystallization kinetics and melting behavior of EAA with different acrylic acid content

Non-isothermal crystallization kinetics and subsequent melting behavior for three kinds of ethylene-acrylic acid copolymer (EAA) are investigated via differential scanning calorimetry (DSC). From the Jeziorny method, the crystallization rate of the primary stage is significantly influenced by the competitive mobility of chains. While the crystallization rate in the secondary stage decreases in order of acrylic acid (AA) content in copolymers. Mo’s method can also provide a good fitting. Difference between the Jeziorny method and Mo’s method analysis is because of a higher effect of non-crystallizable chain ends. The effective activation energy is also determined via Kissinger’s method.     

Extraction of domoic acid from seawater and urine using a resin based on 2-(trifluoromethyl)acrylic acid

A new solid-phase extraction (SPE) matrix with high affinity for the neurotoxin domoic acid (DA) was designed and tested. A computational modelling study led to the selection of 2-(trifluoromethyl)acrylic acid (TFMAA) as a functional monomer capable of imparting affinity towards domoic acid. Polymeric adsorbents containing TFMAA were synthesised and tested in high ionic strength solutions such as urine and seawater. The TFMAA-based polymers demonstrated excellent performance in solid-phase extraction of domoic acid, retaining the toxin while salts and other interfering compounds such as aspartic and glutamic acids were removed by washing and selective elution. It was shown that the TFMAA-based polymer provided the level of purification of domoic acid from urine and seawater acceptable for its quantification by high performance liquid chromatography-mass spectrometry (HPLC-MS) and enzyme-linked immunosorbent assay (ELISA) without any additional pre-concentration and purification steps.     

Water-absorption capacity of cross-linked copolymers of acrylic acid and acrylamide,containing various ionic groups

Radical copolymerization of acrylic acid with acrylamide in the presence of sodium 1,3-diallyl isocyanurate cross-linking agent was studied.     

Wettability of carbon fibers modified by acrylic acid and interface properties of carbon fiber/epoxy

The oxidation-reduction and pre-irradiation induced methods were employed to study the effect of acrylic acid modification on the wetting and adsorption ability of carbon fiber (CF) in epoxy solution and the interfacial properties of CF/epoxy. Systematic experimental work was conducted to determine the surface topography, surface energy, surface chemical composition, absorbability and tensile strength of carbon fibers and interfacial adhesion of CF/epoxy before and after modification. The roughness, surface energy, amount of containing-oxygen functional groups and wetting ability were all found to increase significantly after modifications. The tensile strength of carbon fibers was improved marginally by γ-ray pre-irradiation while was decreased little by oxidation-reduction modification. Consequently, the surface modifications of carbon fibers via both oxidation-reduction and pre-irradiation led to an improvement (more than 15%) of the interlaminar shear strength of CF/epoxy composites. The mechanisms of interfacial improvement of modified CF/epoxy composites are proposed.     

Synthesis and characterization of magnetic poly(acrylic acid) hydrogel fabricated with cobalt nanoparticles for adsorption and catalytic applications

The present study aimed to synthesize poly(acrylic acid) hydrogel embedded with magnetic cobalt (Co) nanoparticles and to investigate their potential in adsorption and catalysis. The hydrogel was prepared by facile free radical polymerization reaction and Co nanoparticles were fabricated within hydrogel by reducing Co (II) ions using NaBH₄ as reducing agent. Co nanoparticles within hydrogel system imparted magnetic properties to the resulting composite gel and also increased the adsorption capacity. The swelling study of hydrogel was carried out by gravimetric analysis. Different functional groups were identified by Fourier Transform Infrared Spectroscopy and Transmission Electron Microscopy analysis was done to investigate dispersion of Co nanoparticles in hydrogel. The bare hydrogel along with Co nanoparticles loaded gel were tested as adsorbent systems for the removal of a cationic dye (methylene blue) from aqueous solution. 95% removal of methylene blue was achieved with a highest adsorption capacity of 836.5 mg/g of adsorbent. The famous adsorption isotherms were used to evaluate adsorption data. Results showed that Freundlich isotherm model was followed with R² value of 0.95. The hydrogel was also used for catalytic reduction in a toxic pollutant, i.e., 4-nitrophenol. Experimental data for 4-nitrophenol reduction followed pseudo first order kinetics model. Activation energy and apparent rate constant were calculated as 9.24 kJ/mol and 0.24 min⁻¹, respectively. Recycling of the magnetic poly(acrylic acid) hydrogel fabricated with Cobalt nanoparticles was carried out for four consecutive cycles and no significant loss in catalytic activity was observed.

     

Effect of copolymer architecture on the response of pH sensitive fibers based on acrylonitrile and acrylic acid

Copolymers of acrylonitrile and acrylic acid with high acrylic acid feed ratio of 43 mol% were synthesized using free radical polymerization. The architecture of copolymers was modified by regulating the dosing of more reactive comonomer-acrylic acid. ¹³C NMR analysis confirmed that two copolymers - one (A) containing enriched blocks of individual monomer-residues (architecture close to a block copolymer) and the second (B) having nearly random distribution of the comonomers, could be successfully synthesized. The resultant acrylic acid content was determined to be nearly 50 mol% for both the copolymers. These copolymers were converted to fine fibers by solution spinning in DMF-water system, drawn in coagulation bath, and annealed at 120 °C for 2 h. The fibers were evaluated for pH response behavior, mechanical stability, and retracting stresses. The fiber A was found to have significantly higher swelling percentage (3300-3700%), faster response, and higher stability to repeated cycling compared to fiber B. Also, Fiber A showed lower thermal shrinkage, better mechanical properties during swelling and higher retracting forces during deswelling. These results indicate that the copolymer with enriched block architecture could possibly form segregated domain structure with acrylic acid domains facilitating enhanced pH response while acrylonitrile domains providing physical crosslinks for stronger mechanical strength. The study suggests that above approach may be more useful than chemically cross-linked gel rods in producing artificial muscles with faster response and good mechanical properties.     

Characterization and antimicrobial properties of metal complexes of polypropylene fibers grafted with acrylic acid using gamma irradiation

Polypropylene fibers were treated against microbial effects by gamma radiation‐induced grafting of acrylic acid, followed by metal complexation with Zn²⁺ or Ag⁺ metal ions. The treated polypropylene fibers were characterized by using Fourier transform infrared spectroscopy and scanning electron microscopy. The effect of the treatment on the thermal stability was investigated by using thermogravimetric analysis, in which a slight increase in the major thermal stability was observed. The antimicrobial activity of the treated fibers was also evaluated. On the basis of the obtained results, it was found that the antimicrobial properties of the treated fibers were enhanced both qualitatively, as indicated by the distinct inhibition zone diameter towards Gram‐positive as well as Gram‐negative bacterial strains under study, and quantitatively, in which 100% inhibition of Staphylococcus aureus and Escherichia coli was achieved. Copyright © 2015 John Wiley & Sons, Ltd.