Simultaneous Radiation Grafting Research Articles

Flame Retardancy of Short Flax Fibers Modified by Radiation-Induced Grafting of Phosphonated Monomers: Comparison between Pre- and Simultaneous Irradiation Grafting.

Short flax fibers have been modified by radiation-induced grafting using methacrylate monomers containing phosphorus to give them a flame-retardant character. Two methodologies, namely pre-irradiation and simultaneous irradiation grafting, were examined. Certain parameters, notably the dose and the irradiation source (e-Beam and γ rays), were evaluated. The grafting efficiency, in terms of phosphorus content (mass percentage), was measured by X-ray fluorescence spectrometry (XRF). Using simultaneous irradiation, 2.39 wt% phosphorus could be obtained from 10 kGy, compared to 100 kGy in pre-irradiation. Furthermore, for similar phosphorus levels, the location of the grafted polymer chains was different for the two methodologies. The effect of phosphorus content on thermal properties and fire behavior was evaluated on a microscopic scale using a pyrolytic flow combustion calorimeter (PCFC) and on a laboratory scale using a cone calorimeter. It was then pointed out that flammability was linked to the phosphorus content and likely its location, which is associated with the radiation-induced grafting methodology, showing that the grafting conditions influence the final fire properties. Simultaneous irradiation, thus, proved to be more interesting in terms of efficiency and final properties.

Adsorption of Zn(II) from aqueous solution and separation of zinc isotopes by displacement chromatography using chelating adsorbent

The removal of zinc ions (Zn(II)) in water and the separation of zinc isotopes were fully investigated in this study. Imidodiacetic acid (IDA) type adsorbent (named PSGI) based on polystyrene spheres (PS) was synthesized by simultaneous irradiation grafting. By adsorption method, the removal of Zn(II) from water by the chelating adsorbent was studied in batch experiments. Under optimized condition, PSGI showed the removal efficiency of more than 98 % for Zn(II) and the adsorption capacity of 70.1 mg/g. Langmuir isothermal and pseudo-second-order kinetic model fitted the experimental results better, indicating that the adsorption is dominated by chemical adsorption. The spent adsorbent (PSGI-Zn) was used for further zinc isotope separation by displacement chromatography using EDTA-NH4 solution as eluent. Due to the mass effect of isotopes, 70Zn was found to preferentially fractionated into the front-end effluents with the highest front enrichment values of 70Zn/64Zn. By extending the migration distance to 20 m, we obtained the best isotope enrichment with the front maximum enrichment values as 1.0949, 1.0739 and separation coefficient values as 1.977 × 10−3, 8.33 × 10−3 corresponding to the isotope pairs 66Zn/64Zn, 68Zn/64Zn.

Tailoring Acid Free-Paper based Analytical Devices (Af-PADs) via radiation assisted modification of cellulose paper

A novel green fabrication approach is being proposed based on radiation assisted modification of Whatman filter paper 1 (WFP) for development of Acid Free-Paper based Analytical Devices (Af-PADs). Af-PADs exude immense potential as handy tools for on-site detection of toxic pollutants such as, Cr(VI), boron, etc., which have established detection protocols involving acid mediated colorimetric reactions that necessitate external acid addition. The proposed Af-PAD fabrication protocol asserts its novelty through elimination of external acid addition step, making the detection process safer and simpler. To achieve this, poly(acrylic acid) (PAA) was grafted onto WFP via a single step, room temperature process of gamma radiation induced simultaneous irradiation grafting, introducing acidic -COOH groups in the paper thereon. Grafting parameters namely, absorbed dose and concentrations of monomer, homopolymer inhibitor and acid were optimized. The -COOH groups incorporated in PAA-grafted-WFP (PAA-g-WFP) provide localized acidic conditions for colorimetric reactions between pollutants and their sensing agents, anchored on the PAA-g-WFP. Af-PADs loaded with 1,5-diphenylcarbazide (DPC) have been ably demonstrated for visual detection and quantitative estimation of Cr(VI) in water samples using RGB image analysis, with LOD value of 1.2 mg.L−1 and a measurement range comparable to that of commercially available PADs based Cr(VI) visual detection kits.

CellUSorb: A high-performance, radiation functionalized cellulose based adsorbent for Uranium (VI) remediation in ground water

A state of the art, phosphate functionalized cotton cellulose based green U(VI) adsorbent has been synthesized via single step, 60Co gamma radiation mediated simultaneous irradiation grafting process, wherein bis(2-methacryloxyethyl) phosphate (B2MEP) was grafted onto cotton cellulose fabric. Samples were characterized using 13C NMR, FTIR, EDXRF, XRD and SEM techniques. Poly(B2MEP)-g-cellulose adsorbent (CellUSorb) was tested for removal of Uranyl (U(VI)) ions from water, adsorption capacities being 79.9 mg.g−1 and 135.9 mg.g−1 in batch and column modes, respectively. The equilibrium adsorption data were analyzed using Langmuir, Freundlich and Redlich-Peterson isotherm models, and kinetic data using pseudo first order, pseudo second order, intra-particle diffusion and Boyd’s models. The adsorbent viability was enhanced through regeneration achieved using ammonium oxalate as eluent, ensuring reusability for five cycles with < 20 % attrition loss/cycle. A standalone, portable water treatment set up, housing a ∼ 100 g CellUSorb cartridge (maximum theoretical U(VI) adsorption capacity ∼ 27,200L for [U(VI)] = 500 µg.L−1), has been conceptualized, fabricated and successfully tested for U(VI) removal to < 30 µg.L−1 (WHO permissible limit) from contaminated water. With potential upscaling for large scale, onsite U(VI) remediation, CellUSorb is a promising prospect that spotlights the role of cellulose in accomplishing UNO’s Sustainable Development Goal of “clean water for all” (SDG6).

Efficient removal of 110mAg nanoparticles (110mAg Nps) in nuclear wastewater by Amines-containing anionic adsorbent PP-g-GMA@EDA

110mAg nanoparticles (110mAg Nps) is a radioactive contaminant in the process wastewater of nuclear power plants. In this study, the novel material containing amines PP-g-GMA@EDA as the adsorbent is proposed for the removal Ag Nps. PP-g-GMA@EDA is synthesized by γ ray-induced simultaneous irradiation grafting and its removal performances for Ag Nps from aqueous solutions has been studied. In Ag Nps solution at different pH values, PP-g-GMA@EDA possesses better removal efficiency than the commercial resin IRN9766 commonly used in nuclear power plants, especially at pH 4. XPS helps confirm that the adsorption mechanism is mainly ion exchange to negatively-charged Ag Nps by protonated secondary amines on the adsorbent. At the optimal pH 4, the effects of different parameters such as the initial Ag Nps concentration, the ratio of adsorbent dosage to solution volume and the adsorption time on adsorption performances are considered. 100% adsorption efficiency of Ag Nps can be achieved and the maximum adsorption capacity is 101.44 mg/g. The Langmiur isotherm model and the pseudo-first-order kinetic model better describe the adsoption process. In the simulated nuclear power plant process wastewater, even though the concentration of competitive ions is 40 times that of Ag Nps, the removal efficiencies still maintain above 85%. In addition, 5 wt% ammonia water can effectively desorb Ag Nps from the used adsorbent to ensure the recyclability of PP-g-GMA@EDA. The well designed adsorbent with excellent removal efficiency and selectivity provides a very efficient, sustainable, and industrially feasible way for Ag Nps decontamination from nuclear wastewater.

Highly promising recycled low-density polyethylene sheet adsorbents for uranium recovery from seawater

ABSTRACT Amidoximated absorbers based on recycled low-density polyethylene (LDPE) sheets (food packaging bags, breast milk storage bags and grocery bags) for uranium recovery from seawater were investigated. Simultaneous irradiation grafting by gamma ray was performed. A 40-µm thick LDPE sheet submerged in the acrylonitrile (AN): methacrylic acid (MAA) solution of 60: 40 v/v% with the optimal gamma ray dose of 40 kGy showed the highest cografting degree of 85.28% and the highest amidoxime group density of 4.38 mol/kg. The field study was performed along the coastal area of the Gulf of Thailand. After 56 days of soaking, the highest adsorption capacity reached 1.79 g-U/kg-adsorbent. The reusability study for up to 6 cycles revealed about 20% of the adsorption capacity remaining in the last cycle. The study demonstrated that recycled LDPE sheets can be utilized as a substrate to synthesize uranium absorbers. It showed an acceptable uranium loading with good reusability in natural seawater environment. This method of reusing discarded LDPE sheets also helps alleviate environmental issues of non-degradable plastic wastes.

Investigations on amidoxime grafted sepiolite based chitosan organic–inorganic nanohybrid composite beads towards wastewater detoxification

This work explores the fabrication of organic–inorganic nanohybrid based biopolymer composite systems for the cleaning of different contaminants from wastewater. This system involves the simultaneous radiation grafting techniques for sepiolite (SP) modification and the simple mixing of modified-SP with biopolymer matrix, chitosan (CS). The SP beads were chemically modified with amidoxime prior to its use in composite systems. The synthesized composite beads were characterized using scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), nitrogen physical adsorption (BET) investigations, Fourier transform infrared (FT-IR), atomic absorption and UV–visible spectroscopy. Hydrolytic stability of beads was also investigated in aqueous media, beads showed excellent stability in aqueous medium and in acidic environment. Here, the sorption profile of copper over amidoxime grafted SP-nanohybrid (MSP) incorporating CS-beads is reported. Furthermore, the key adsorptive variables, i.e. contact time, adsorbent dose, and concentration of adsorbate are discussed. Different isothermal (Langmuir and Freundlich) and kinetics model were also elaborated. Langmuir isotherm and pseudo-second-order models are proved to be the best fit models for Cu (II) removal in aqueous system. To explore the efficacy of the material towards organic pollutants, methylene blue (MB) was selected as model compound and adsorbed on nanohybrid beads. The results revealed that organic–inorganic nanohybrid incorporating CS beads are quite effective for contaminated water remediation, owing to their better adsorptive performance, high stability and easy application.

Synthesis of modified sepiolite-g-polystyrene sulfonic acid nanohybrids by radiation induced graft polymerization

In this study, polystyrene (PS) grafted sepiolite nanohybrid (MS-g-PS) was synthesized by using simultaneous radiation grafting technique in the presence of dichloromethane (DCM) as solvent. The radiation grafting process was carried out under inert atmosphere at room temperature using gamma rays from a Co-60 irradiator. The degree of grafting was affected by absorbed dose and monomer concentration in the mixture. Sulfonation of synthesized nanohybrid was carried out with sulfuric acid. Both the grafting of styrene and its sulfonate derivative were verified by Fourier transform infrared spectroscopy (FT-IR). The structural and morphological investigations of these nanohybrids have been investigated by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The gravimetric investigations showed that grafting yield increases with the absorbed dose. Results showed that the system allows the controlled grafting of styrene onto sepiolite (Sep) in DCM.

Removal of copper using novel amidoxime based chelating nanohybrid adsorbent

Novel poly(acrylonitrile) grafted sepiolite nanohybrid material (RGS) has been synthesized by using simultaneous radiation grafting technique. The grafting yield was measured by varying the absorbed dose and monomer concentration in the mixture. The acrylonitrile group present in nanohybrid material was chemically modified into amidoxime. Both the grafting yield and degree of conversion of acrylonitrile to amidoxime was examined by gravimetric analyses. The structural and morphological investigations of these nanohybrid materials were performed by FT-IR, XRD and FESEM. Batch adsorption studies were carried out for copper uptake onto amidoximated nanohybrid adsorbents to envisage the effects of pH, adsorbent dose, contact time and initial concentration. Removal of copper ion attained equilibrium within 30 minutes following pseudo-second order kinetics. The equilibrium process was well described by the Langmuir isotherm model and the maximum adsorption capacity (Qm) was found to be 278mg/g for 5kGy irradiated sample. This environmental friendly and cost effective adsorbent can be used for the removal of copper ion from aqueous solutions.

Effects of RAFT Agent on the Chloromethylstyrene Polymerizations in a Simultaneous Radiation Grafting System.

Reversible addition-fragmentation chain transfer (RAFT) agent was added into a simultaneous radiation grafting system and its effects on graft polymerization and homopolymerization were investigated. Chloromethylstyrene (CMS) was graft polymerized onto ethylene-tetrafluoroethylene copolymer (ETFE) films under γ-ray sources via simultaneous irradiation. The non-grafted poly(CMS) in the grafted films were extracted by xylene at 120 °C. The poly(CMS) was characterized by NMR and GPC instruments. Addition of the RAFT agent suppressed both graft polymerization and homopolymerization. However, under a high concentration of RAFT agent, the homopolymerization in the monomer solution could occur through a typical RAFT polymerization while polymerization in the ETFE films proceeded via RAFT and conventional radical polymerization, resulting in poly(CMS) in the ETFE films with molecular weight dispersity higher than 1.0 but lower than that without RAFT agent. Furthermore, it was found that the molecular weight of the poly(CMS) in the ETFE films was several times higher than that of the poly(CMS) in the monomer solution.

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.

Optimization of acrylic acid grafting onto polypropylene using response surface methodology and its biodegradability

Simultaneous radiation grafting was optimized to graft acrylic acid monomer on the polypropylene (PP) films to make them hydrophilic and enhance their biodegradability. Experiments were designed based on full factorial central composite design (response surface methodology) and influence of monomer concentration, radiation dose, inhibitor concentration, solvent concentration on degree of grafting was investigated. The extent of grafting was found to increase with increasing monomer concentration, inhibitor concentration and radiation dose. The targeted 35% grafting could be achieved at optimum condition viz. monomer concentration 12.09wt%, radiation dose 12.40 kGy, inhibitor concentration 0.07M and solvent concentration 0.12M. The grafted PP films at different degrees of grafting were tested for tensile properties and characterized by swelling studies, fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). Successful grafting of acrylic acid onto polypropylene films was indicated by FTIR and confirmed quantitatively by determination of carboxylic groups on the film surface. Tensile strength of grafted PP films decreased with increase in degree of grafting. The crystallinity of the grafted PP films was lower than that of PP film as indicated by DSC studies. Grafting of acrylic acid increased the roughness on the surface of PP films indicated by SEM studies. The maximum biodegradability of the 34.55% grafted film was 5.5%.

Catalase immobilized-radiation grafted functional cellulose matrix: A novel biocatalytic system

The work highlights a unique, one step protocol for room temperature immobilization of enzyme catalase onto epoxy functionalised cellulose matrix developed via gamma radiation induced simultaneous irradiation grafting of Glycidylmethacrylate (GMA). Effect of grafting parameters, such as radiation dose, monomer concentration and solvent composition on the grafting yield, was studied in order to optimize the radiation grafting process. Poly(GMA)-g-cellulose matrices were characterized by grafting yield determination, FTIR, SEM and TGA techniques. The epoxy functionalized poly(GMA)-g-cellulose matrix was subsequently employed for covalent immobilization of an industrially relevant enzyme catalase. The catalytic activity of catalase-immobilized-poly(GMA)-g-cellulose was assayed by spectrophotometrically monitoring the enzymatic degradation of H2O2 at 240nm. Catalase-immobilized-poly(GMA)-g-cellulose was observed to be reusable for over 5 cycles within ten days. Catalase was observed to show improved activity at higher pH after immobilization. Thermal stability of Catalase-immobilized-poly(GMA)-g-cellulose was also enhanced in comparison to the free enzyme system.

Morphological Study of Poly(vinylbenzyl chloride)-Grafted Poly(ethylene-co-tetrafluoroethylene) [ETFE-g-PVBC] Films Using Small-Angle Neutron Scattering Analysis.

In this study, the effect of degree of the grafting and crosslinking on the morphology of the crystalline domain in poly(vinylbenzyl chloride)-grafted poly(ethylene-co-tetrafluoroethylene) [ETFE-g-PVBC] films was investigated using a SANS (small-angle neutron scattering) analysis. The grafted films can be used as a precursor for ion-exchange membrane. ETFE-g-PVBC films with various degrees of cross-linking were prepared by a simultaneous irradiation grafting of vinylbenzyl chloride (VBC) and divinylbenzene (DVB) onto an ETFE film. The SEM-EDX (scanning electron microscopy-energy dispersive X-ray spectroscopy) results of a cross-sectional distribution of ETFE-g-PVBC films showed that the chlorine atoms were well-distributed throughout the films. SANS profiles of the PVBC-grafted films in the absence of a DVB crosslinker showed that the crystalline domain peaks were observed and the peak maximum position shifted significantly from 0.032 Å-(-1) to 0.02 Å(-1) with an increase in the degree of grafting. However, peak maximum positions of the PVBC-grafted films in the presence of a DVB crosslinker shifted slightly from 0.02 Å(-1) to 0.024 Å(-1) with an increase in the amount of DVB monomer at same degree of grafting. These results indicate that the degree of grafting and crosslinking affect the morphology of the crystalline domain in the ETFE-g-PVBC films.

Ethylene vinyl acetate based radiation grafted hydrophilic matrices: Process parameter standardization, grafting kinetics and characterization

A transparent, elastomeric, grafted matrix for several potential applications was synthesized by single-step simultaneous radiation grafting of methacrylic acid onto ethylene vinyl acetate (EVA). CuSO4 was found to be the most suitable homo-polymerization inhibitor among different inhibitors tried. The grafting kinetics was found to be a strong function of dose rate (D) and monomer content (M) and an equation relating grafting rate Rg=Kg [M]1.13D0.23 was deduced. Crystallinity of the grafted matrices as assessed from XRD and DSC measurements indicated decrease in crystalline content with increase in grafting yield, suggesting crystalline domain of EVA get disrupted on grafting. Elastic modulus increased linearly with the increase in grafting yield, though elongation at break decreased precipitously from 900% to 30% at even ~9% grafting. Thermo-gravimetric analysis showed three step weight loss of the grafted EVA matrix. The grafting of MAA resulted in increase in surface energy mainly due to enhanced polar component.

Adsorption of Re and 99Tc by means of radiation-grafted weak basic anion exchange resin

To avoid using toxic solvents, weak basic anion exchange resin with aromatic amine groups was prepared by grafting 4-vinyl pyridine onto polystyrene microspheres through simultaneous radiation grafting method. In batch adsorption experiments toward Re(VII) which was selected to simulate 99Tc, the adsorption efficiency maximized when the concentration of HNO3 was set at 0.02 M. Using reductive eluents SnCl2 it was found a method to efficiently regenerated resin at low acidity. For adsorption toward 99Tc, the results matched well with Re, which indicates that the prepared exchangers will have wide applications in the future to remove 99Tc from spent nuclear fuel.

Anisotropic radio-chemically pore-filled anion exchange membranes for solid alkaline fuel cell (SAFC)

Anion exchange pore-filled membranes based on meso-porous polyethylene support are fabricated through a radio-chemical grafting process. Vinylbenzylchloride (VBC) monomers are grafted onto porous polyethylene substrate by a simultaneous irradiation grafting method. The porous polyethylene substrate provides high chemical and mechanical stability. The pore-filled membranes are subsequently functionalized by trimethylamine (TMA) and ion exchange with sodium hydroxide, yielding alkaline anion exchange membranes that are capable of conducting hydroxide ions. The meso-porous support structure contributes to a reduction in dimensional swelling while maintaining high water uptake, high ion exchange capacity, and enhanced mechanical strength of over 50MPa. In particular, these radio-chemically pore-filled membranes exhibits anisotropic through-plane oriented ion conductive behavior due to the low resistance of the hydrated cross-sectional structure derived from the nonwoven porous substrate. As a result of reinforced mechanical strength and anisotropic electrochemical property, the membrane exhibits good membrane-electrode assembly (MEA) performance (at 0.6V, max. current density=174mAcm−2 and max. power density=127mWcm−2) in solid alkaline fuel cell.

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.

Highly cross-linked poly(styrene sulfonic acid)-grafted poly(tetrafluoroethylene-co-perfluoropropyl vinyl ether) membranes with various thicknesses and their application to direct methanol fuel cell

Highly cross-linked poly(styrene sulfonic acid)-grafted poly(tetrafluoroethylene- co-perfluoropropyl vinyl ether) (PFA- g-PSSA) membranes with various thicknesses have been successfully prepared through the simultaneous irradiation grafting of styrene/divinylbenzene (DVB) onto PFA films with thicknesses of 25, 50, and 100 μm followed by sulfonation to introduce sulfonic acid moiety. It was observed that a concentrated chlorosulfonic acid solution and a high reaction temperature are needed to provide sufficient sulfonic acid as the thickness of the PFA films and the content of DVB both increase. The physicochemical properties of the prepared membranes such as water uptake, proton conductivity, methanol permeability, and chemical stability, were also investigated in this study.

Poly(vinylbenzyl sulfonic acid)-grafted poly(ether ether ketone) membranes

In this study, an aromatic hydrocarbon based polymer electrolyte membrane, poly(vinylbenzyl sulfonic acid)-grafted poly(ether ether ketone) (PEEK-g-PVBSA), has been prepared by the simultaneous irradiation grafting of vinylbenzyl chloride (VBC) monomer onto a PEEK film and subsequent sulfonation. Each chemical conversion was monitored by FT-IR and SEM–EDX instruments. The physicochemical properties including IEC, water uptake, proton conductivity, and methanol permeability of the prepared membranes were also investigated and found that the values of these properties increase with the increase of degree of grafting. It was observed that the IEC values of the prepared PEEK-g-PVBSA membranes with 32%, 58%, and 80% DOG values were 0.50, 1.05, and 1.22meq/g while the water uptakes were 14%, 20%, and 21%, respectively. The proton conductivities (0.0272–0.0721S/cm at 70°C) were found to be somewhat lower than Nafion 212 (0.126S/cm at 70°C) at a relative humidity of 90%. However, the prepared membranes showed a considerably lower methanol permeability (0.61–1.92×10−7cm2/s) compared to a Nafion 212 membrane (5.37×10−7cm2/s).