Ion-exchange Groups Research Articles

Effect of gamma irradiation on ammonium ion production and ion exchange capacity of pyridinium-type anion exchange resin

Radiolysis of pyridinium-type exchange resin has been investigated by gamma-ray irradiation. This study focused on the effect of absorbed doses, pH and NO3− concentrations on the NH4+ concentrations and the changes of ion exchange capacity (IEC) after irradiation. It was found that hydrated electron could destroy the resin to generate pyridine and polymeric phenacyl radical, and pyridine was further degraded to NH4+. Test results of IEC showed 2% ion exchange groups were lost from resin in 5 mol/L HNO3 at 100 kGy absorbed dose. Adsorption efficiency of irradiated resin under the absorbed dose of 100 kGy for TcO4− was 94.3%.

Adsorption characteristics and mechanism of Pb(II) by agricultural waste-derived biochars produced from a pilot-scale pyrolysis system

The objective of this study was to investigate the feasibility of removing Pb2+ by pilot-scale fluidized bed biochar, and then to put forward an industrial-scale fluidized bed pyrolysis progress of cogeneration of biochar and high-temperature gas. Corn stalk biochars (CSBs) were prepared at 400–600 °C, in which the maximum Pb2+adsorption capacity (Qm) of CSB450 is 49.70 mg⋅g−1 at the optimal condition. Adsorption isotherms, kinetics, and thermodynamics were determined, and Pb2+-loaded biochar was analyzed by fourier transform infrared spectroscopy (FTIR), x-ray photoelectron spectroscopy (XPS), x-ray diffraction (XRD) and scanning electron microscope with energy dispersive spectrometer (SEM-EDS). Ion exchange, complexation and mineral precipitation together contributed to Pb2+ adsorption on CSBs. For high-temperature CSBs with fewer oxygen functional groups (OFGs) and stronger aromatization, Pb2+ adsorption by ion exchange and functional group complexation was reduced. The mineral precipitationwas formed during the adsorption process. Using the pilot-scale fluidized bed in this study, the carbon yield per year would achieve 31.79 t, and about 1.58 t of Pb2+ would be adsorbed according to the adsorption capacity at the pyrolytic temperature of 450 °C.The results are beneficial to screen for effective biochar as a cost-effective industrial adsorbent to remove Pb2+ in contaminated water.

Three-Dimensional Stable Cation-Exchange Membrane with Enhanced Mechanical, Electrochemical, and Antibacterial Performance by in Situ Synthesis of Silver Nanoparticles.

In this study, a simple and facile approach was proposed to synthesize silver nanoparticles (AgNPs) loaded cation-exchange membranes (CEMs). A wide analytical study involving scanning electronic microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy was accomplished to corroborate that the in situ generated AgNPs were uniformly dispersed in the polymer matrix. In addition, as a result of the proposed synthesis strategy, the cross-linking structure inside the membrane was formed. The proper particle size and dispersibility of the AgNPs improved the mechanical properties of the membranes. Besides, the optimal AgNP-loaded CEM exhibited excellent bacterial killing activities against Gram-negative bacteria and showed a controlled improvement in the electrochemical performance of the prepared membranes. These effects were caused by the obtained distribution of AgNPs near ion-exchange groups that increased the aggregation of water molecules around them, improving the efficiency of ion transport due the formation of array broad ion-transport channels. The optimized CEM [sulfonated polysulfone (60SPSF)-C3#-Ag-2] exhibited an enhanced NaCl removal ratio of 67.5% with a high current efficiency (96.9%) and a low energy consumption (5.84 kWh kg–1). The distance of the inhibition zone from the boundary of the membrane of SPSF-C3#-Ag-2 reached 4.8 mm. These results led us to suggest that the proposed synthesis strategy may have potential applications in the field of antibacterial and desalting ion-exchange membranes.

Protein adsorption to poly(ethylenimine)-modified Sepharose FF: VIII: Impacts of surface ion-exchange groups at different polymer grafting densities

Our previous studies on protein adsorption to the anion-exchangers of poly(ethylenimine) (PEI)-grafted Sepharose FF found that both adsorption capacity and uptake rate of bovine serum albumin (BSA) increased greatly when the PEI grafting density reached over a critical ionic capacity (cIC) due to the 3D protein binding and occurrence of “chain delivery” of bound proteins. Moreover, by the investigation on the anion-exchangers of diethylaminoethyl (DEAE)-modified and DEAE-dextran-grafted Sepharose FF, we found the unique role of surface ligand in facilitating protein uptake kinetics on dextran-functionalized anion exchangers as the “transfer station” for the “chain delivery” of bound proteins. However, what would be the contribution of surface ligands on the transport of bound proteins on PEI chains at a wide range across cIC, particularly at the lower IC range where no “chain delivery” was present? We have thus designed this research to answer the question. To this purpose, we fabricated three series of PEI-Sepharose FF resins, one without surface ligand (i.e., FF-PEI) and two with surface DEAE modifications at DEAE coupling densities of 60 and 90 mmol/L (i.e., FF-D60-PEI and FF-D90-PEI), and focused on the role of surface DEAE at different PEI densities in BSA adsorption equilibrium and uptake kinetics in a wide IC range of PEI across cIC (∼600 mmol/L for BSA). It was found that, at low grafting-ligand densities (IC<cIC), both adsorption capacity and uptake rate increased significantly (5–14% and 40–140%, respectively) after adding surface DEAE groups. At IC > cIC, however, both adsorption capacity and uptake rate changed only slightly (<5% and <10%, respectively) by the addition of surface DEAE groups. The results revealed that at IC < cIC, the surface DEAE groups provided the supplement of available binding sites and facilitated the happenings of the “chain delivery” of bound proteins as the “transfer station”, both of which were limited at the low IC range. However, at IC > cIC, the extended flexible PEI chains have already afforded 3D binding space with high accessibility and easy happening of “chain delivery” of bound proteins, so the surface DEAE groups between neighboring PEI chains did not work in assisting the transport of bound proteins. Moreover, when the IC was lower but close to the cIC, the FF-D-PEI resins exhibited higher uptake rates than FF-PEI resins at a similar or even lower IC values. These findings indicate that surface modification of charged groups in PEI-based anion exchangers of low grafting density would be an efficient strategy to fabricate high performance protein ion exchangers.

Electrostatically-coupled graphene oxide nanocomposite cation exchange membrane

We report the preparation of an electrostatically-coupled graphene oxide nanocomposite cation exchange membrane (CEM) based on sulfonic group containing graphene oxide (SGO) (45 wt % loading) and polyvinylidene fluoride (PVDF), where the ion exchange groups were provided by the SGO additive. SGO was prepared via the mixing of graphene oxide (GO) with a mixture derived from 3,4-dihydroxy-l-phenylalanine (l-DOPA) and poly(sodium 4-styrenesulfonate) (PSS). A mold-casting technique was developed to fabricate the free-standing nanocomposite CEM. The presence of sulfonic groups in the nanocomposite was confirmed with FTIR spectroscopy. Energy dispersive spectroscopy analysis showed the SGO was distributed across the entire membrane matrix, with minimal aggregation. The resultant SGO/PVDF nanocomposite CEM membrane demonstrated high hydrophilicity and high water uptake, but low swelling ratio. Furthermore, evaluation of the electrochemical properties of the nanocomposite CEM showed favorable ion exchange capacity (0.63 ± 0.08 meq/g), permselectivity (0.95 ± 0.04), and area resistance (2.8 ± 0.2 Ω cm2). The nanocomposite CEM show good potential for use in electromembrane desalination applications.

Optimization and mechanisms of biosorption process of Zn(II) on rape straw powders in aqueous solution.

The different part powders of rape straw as adsorbents were performed to remove zinc ions from aqueous solution in this work. The various factors on influencing removal efficiency of Zn(II) were investigated, and the operational conditions were optimized using the Box-Behnken design of response surface methodology (RSM). Under the optimum conditions obtained, the removal rates of Zn(II) were attained to 100.00%, 78.02%, and 17.00% by straw pith core, seedpods, and shell of rape straw, respectively. Equilibrium and kinetic models were applied to evaluate the adsorption behaviors of Zn(II) on the adsorbents. The equilibrium data were best described by the Langmuir isotherm model, which indicated that the adsorption behaviors were favorably monolayer adsorption processes. The biosorption capacities of Zn(II) were 34.66mgg-1, 36.41mgg-1, and 36.74mgg-1 of rape straw pith core; 23.33mgg-1, 23.85mgg-1, and 24.30mgg-1 of seedpods; and 11.19mgg-1, 11.23mgg-1, and 11.27mgg-1 of shell, respectively, at the various temperatures of 20°C, 30°C, and 40°C based on Langmuir isotherm equation. The pseudo-second-order kinetic model was well to determine the adsorption kinetics, which suggested that ion exchange were occurred during adsorption processes of Zn(II). The characteristics of adsorbents before and after adsorption of Zn(II) were measured using the methods of scanning electron microscope (SEM), zeta potential classes, energy dispersive spectrometer (EDS), and Fourier transform infrared spectroscopy (FT-IR), respectively. The results provided evidences for the adsorption mechanisms of Zn(II) including electrostatic attraction, ion exchange, and functional group involvement on the three part powders of rape straw in aqueous water.

Practical considerations on the particle size and permeability of ion-exchange columns applied to biopharmaceutical separations

The goal of this study was to better understand the possibilities and limitations of modern cation exchange chromatography (CEX) columns for the separation of protein biopharmaceuticals (typically mAbs and related products). Several commercial and research columns consisting of a non-porous polymeric core particle with a thin hydrophilic coating and grafted ion-exchanger sulfonate groups, were compared. The impact of particle size, porosity and packing pressure on the separation of therapeutic proteins was evaluated in a systematic way.First, it was shown that the porosity of modern CEX columns depends on the applied conditions, and lower apparent porosity as well as increased column pressures were observed when using low ionic strength mobile phase (less than 0.01 M NaCl), due to swelling. Column pressure seemed to be dependent on the 1/dp3 to 1/dp5 relationships with particle size, depending on whether 0.3 M NaCl or pure water was used as mobile phase, respectively.Using 5 cm long columns packed with 2 or 2.5 µm particles could easily result in higher than 1000 bar pressure drops when the mobile phase ionic strength is low. Therefore, it is recommended that particle size not be decreased to below 2.5 µm so that technologies can remain compatible with the current state of ultra-high pressure (UHPLC) instrumentation.This recommendation is underscored by the fact that a decrease in particle size does not produce improved separations, since the particles are non-porous (no intra-particle diffusion nor resistance to mass transfer) and that large solutes follow an on-off (bind and elute) type retention mechanism.The only advantage of CEX columns packed with small particles is that they can provide more specific surface area per unit length of column, and thus facilitate higher throughput methods.In conclusion, it appears that there is no need to further decrease the particle size in CEX since decreasing their particle size may result in more drawbacks than benefits.

Novel crosslinked aliphatic anion exchange membranes with pendant pentafluorophenyl groups

To enhance the performance of anion exchange membranes (AEMs) by constructing effective ion channels, we synthesized novel aliphatic polymers with pentafluorophenyl pendent groups via superacid catalyzed polyhydroxyalkylation and quaternization by grafting multi-cation crosslinker through the Menshutkin reaction. The procedure adopted in this study for preparing the AEMs circumvented the utilization of precious metal catalysts and made it easy to control the reaction conditions. Compared with the traditional aliphatic AEMs, the AEMs prepared by the new strategy exhibited well-developed microphase-separated structures by increasing the hydrophilic/hydrophobic difference between the polymer backbones and the side chains. Moreover, the multi-cation crosslinker not only provides ion exchange groups but also constrains the swelling of the AEMs. As we expected, the well-defined ion channels were validated by transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS). The CPFBP-TQA-100 membrane shows a highest ion conductivity of 76.85 mS cm−1 and a swelling ratio of only 24.8% at 80 °C. A maximum power density of 116.7 mW cm−2 is achieved by a single cell using the CPFBP-TQA-100 membrane at a current density of 300 mA cm−2 at 80 °C. Besides, all the AEMs display excellent thermal stability and reasonable alkaline stability.

Structure of Water and Silica in Ion Exchange Resins

Abstract Dynamic and static structures of water sorbed in ion exchange resins have been investigated by 17O NMR and X-ray diffraction. Rotational motion of water molecules sorbed in ion exchange resins is significantly slowed according mainly to the amount of cross-linkage of polymer which decides the size of micropore surrounded by hydrophobic polymer networks, and not crucially affected by the difference of hydration properties of ion exchange groups. Static structure of water sorbed in anion exchange resin is revealed to be similar to that of pure water, which indicates a clathrate like structure enclosing a hydrophobic tetramethylammonium group. On the other hand the structure of water in cation exchange resin is quite different from that of pure water, but resembles the structure found in aqueous sulfuric acid solution, which is strongly influenced by the highly acidic atmosphere. The structure of silica adsorbed in anion exchange resin has also been observed by X-ray diffraction. Obtained radial distribution function is quite similar to that of bulk silica, which requires the existence of Si-O-Si interaction in quantitative analysis. The present results evidence that silica adsorption in anion exchange resin is not simple ion exchange but combined processes of ion exchange and micro silica gel growth.

Modelling of anion-exchange membrane transport properties with taking into account the change in exchange capacity and swelling when varying bathing solution concentration and pH

In this paper we take into account the variation of anion-exchange membrane swelling and effective exchange capacity with changing the concentration and/or pH of the bathing solution when simulating membrane transport characteristics (the electric conductivity, diffusion permeability and ion transport numbers). Two main structural elements of the membrane are distinguished: a microporous polyelectrolyte gel assumed homogeneous, and macropores including structural defects and voids. It is supposed that only microporous gel exerts osmotic pressure, which causes membrane swelling described in our model by the Gregor equation, which employs the mole fractions of free and bound water. Three types of ion-exchange functional groups, namely, the secondary, tertiary and quaternary amino groups are taken into account. The degree of dissociation of these groups depends on the internal solution pH, which is described by equilibriums between protonated and deprotonated forms. The Donnan equations and electroneutrality condition are used to calculate the ion concentration in the membrane. The microheterogeneous model based on the Nernst-Planck equations is used to describe the ion transport. We take into account that the ion diffusion coefficients depend on the degree of gel swelling, this dependence is described by the Mackie-Meares equation. The model parameters include the equivalent volume of dry polyelectrolyte gel, the volume fraction of macropores, the structural parameters and others.The results of calculations are compared with experimental data on the electric conductivity, diffusion permeability and ion transport numbers for two heterogeneous anion-exchange membranes MA-40 and MA-41 (Shchekinoazot, Russia) differed by the fractions of the weakly basic functional groups. A good quantitative agreement between the theory and experiment is found for both membranes using the same set of ion hydration numbers and chemical equilibrium constants for secondary and tertiary amino groups. In particular, it is shown that with increasing pH of the bathing solution, the membrane diffusion permeability passes through a maximum, which is explained by the corresponding maximum of water content. A higher water content results in larger membrane pores, which leads to higher values of ion diffusion coefficients and higher amount of sorbed electrolyte. Together with varying water content, the variation in membrane effective exchange capacity as a function of external solution pH, determines a non-trivial behavior of electric conductivity, diffusion permeability and ion transport numbers in the membrane equilibrated with NaCl solutions of different concentration and pH.

Electrochemical Characterization of Ion Exchange Composite Membrane with Various Ion Exchange Group Moieties

In this study, ion exchange membranes were prepared by sulfonating and aminating the same polymer with different equivalents respectively. Thereafter, the most suitable equivalent amount of the polymer was selected and used for the study. The selected polymer was impregnated into a support in a solution state to prepare a reinforced composite membrane having excellent mechanical strength. The ion exchange capacity tends to decrease with the use of a support. In order to compensate this, the particles are mixed with the polymer solution to maintain the existing performance. FE-SEM was used to confirm particle dispersion in the membrane, and quantitative analysis was performed using FT-IR. In addition, thermal properties were analyzed using TGA and DSC, and electrochemical characteristics were analyzed through ionic conductivity / membrane resistance / I-V curves.

Preparation of tungstic acid functionalized titanium oxide nanotubes and its effect on proton exchange membrane fuel cell

Titanium oxide nano tubes (TNT) were synthesized by hydrothermal method and tungstic acid (ion exchange group) were covalently grafted on its surface. The synthesized tungstic acid functionalized TNT (W-TNT) were characterised by SEM, TEM, XRD analysis for the nano-tubular morphology and the successful grafting of tungstic acid group was confirmed by FTIR and solid state NMR techniques. Composite membranes of different weight percentage W-TNT (2%, 4%, 6% and 8%) and sulfonated poly ether ether ketone (SPEEK) were fabricated which resulted in high ion exchange properties. The prepared composite membranes were characterised by SEM, XRD, FTIR, water uptake, ion exchange capacity and proton conductivity to ensure the aptness of the membranes to be used as electrolyte in fuel cell application. From the studies it was found that SPEEK with 6% W-TNT showed optimum electrochemical properties. Upon testing this membrane in fuel cell as an electrolyte with carbon supported platinum anode and cathode electrodes, a maximum power density of 352 mW cm−2 was achieved at 80 °C. The presence of additional ion exchange groups (tungstic acid) and hollow nature of TNT lead to the improved performance than the plain membrane.

Synergic effect of ionic liquid grafted titanate nanotubes on the performance of anion exchange membrane fuel cell

Titanate nano tubes, prepared by hydrothermal method, are covalently bonded with a basic ionic liquid (1-Methyl-3-(3-trimethoxysilylpropyl) imidazolium chloride) resulting in an ion exchange behaviour. The ionic liquid bonded Titanate nano tubes are characterised by SEM, TEM, XRD studies for their nano tube morphology and covalent bond between them which are confirmed by solid state NMR and FTIR. This synthesised filler, in various concentrations (1, 3, 5 and 7 wt%), are incorporated into quaternised polysulfone leading to the fabrication of nano composite membranes with high ion exchange capacity. The fabricated nano composite membranes are characterised by SEM, XRD, water uptake, ion exchange capacity and hydroxyl conductivity studies to evaluate their suitability as an electrolyte in alkaline fuel cell applications. Upon testing these membranes in fuel cell setup with platinum anode and silver cathode, amongst the various composites, the membrane with 5% wt filler exhibits the most optimum properties for application in alkaline fuel cells with a power density of 302 mW/cm2. The existence of ion exchange behaviour as well as the hollow nature of titanate nano tubes leads to synergistic effect in conducting the hydroxyl ions via both Grotthus (through water molecules) and hopping (through ion exchange groups) mechanisms.

Polyelectrolyte Composite Membranes Containing Electrospun Ion-Exchange Nanofibers: Effect of Nanofiber Surface Charges on Ionic Transport.

Poly(vinyl alcohol) (PVA)-based ion-exchange nanofibers (IEX-NFs) and their composite polyelectrolyte membranes were prepared and characterized. The PVA-based NFs are well dispersed and form a three-dimensional network structure in the polymer matrix, Nafion. All of the prepared membranes show a similar ion-exchange capacity of ∼1.0 mmol g-1. The ionic conductivities through the PVA- b-PSS-NF/Nafion composite membranes are superior to that of the Nafion membranes, but the conductivity through the PVA-NF/Nafion composite membrane is half that of the Nafion membrane. Our electrokinetic measurements clearly indicate that a high density of ion-exchange groups on the NF surface results in a continuous ionic transport path in the polymer matrix. In addition, the mechanical strength of all of the NF-composite membranes is improved compared with that of the membranes without NF.

Visualization and Modeling of Protein Adsorption and Transport in DEAE‐ and DEAE‐Dextran‐Modified Bare Capillaries

This article reports a microscopic method to directly visualize protein adsorption and transport in bare capillaries modified with ion exchange groups. Silica capillaries were coated with poly(vinyl alcohol) to eliminate nonspecific protein absorption and then functionalized with diethylaminoethyl (DEAE) and DEAE‐dextran to prepare anion‐exchange capillaries denoted as D‐C and D‐dex‐C, respectively. Protein concentration profiles acquired from microscopic images were analyzed with a one‐dimensional diffusion‐adsorption model to determine adsorption capacities and effective diffusivities. It revealed that surface diffusion of bound protein on the capillary surface in D‐Cs was negligible, but that of bound proteins markedly contributed to protein transfer in D‐dex‐Cs because of the chain delivery effect of charged dextran chains. The chain delivery was little affected by protein concentration, but significantly increased with ionic capacity. The research thus provided new insight into protein adsorption and transport behaviors on the surfaces modified with ion exchange groups of different structures. © 2018 American Institute of Chemical Engineers AIChE J, 65: 305–316, 2019

Enhanced hydroxide ion conductivity of imidazolium functionalized poly (ether ether ketone) membrane by incorporating N,N,N′,N′-tetramethyl-1,4-phenylenediamine

Anion-exchange membranes (AEM) are prepared from chloromethylated poly(ether ether ketone) (CMPEEK), which is quaternized by N,N,N′,N′-tetramethyl-1,4-phenylenediamine (TMPD) and 1-methylimidazole using a two-step method. TMPD can not only improve the mechanical properties but also provide more ion exchange groups and improve the availability of quaternary ammonium (QA) groups. By varying the amount of TMPD in the membrane casting solution, the comprehensive properties of the membranes are optimized and intensified. The anion conductivity is increased from 0.028 S cm−1 of the imidazolium functionalized poly (ether ether ketone) (ImPEEK) control membrane to 0.042 S cm−1 of the TMPD/ImPEEK membrane with a TMPD content of 5 wt%. Meanwhile, a 31.5% increase in ultimate tensile strength and a 27.8% increase in Young's modulus of the TMPD/ImPEEK membrane are achieved. This study exploited a facile approach to solving the trade-off relation between anion conductivity and mechanical properties.

Phosphonate ionic liquid immobilised SBA-15/SPEEK composite membranes for high temperature proton exchange membrane fuel cells

High temperature proton exchange membrane fuel cells require an electrolyte membrane which is mechanically and thermally more stable for its efficient performance. In the present study, a composite membrane prepared using phosphonate ionic liquid immobilised SBA-15 as filler and SPEEK as matrix has been reported. The imidazolium ionic liquid namely 1-Methyl-3-(3- Trimethoxysilylpropyl) imidazolium chloride was grafted on SBA-15 followed by reacting with monosodium phosphate to afford phosphate ion (H2PO4−) containing SBA-15 (PIL-SBA-15). The structure of PIL-SBA-15 was confirmed by solid state CP/MAS 13C and 31P NMR, FTIR, low angle XRD, BET and TEM analyses. SPEEK composite membranes with different concentrations (2, 4, 6 and 8 wt%) of PIL-SBA-15 was prepared by simple solution casting method. The change in morphology of the composite membranes were studied using SEM and XRD techniques. The ion exchange capacity, proton conductivity at high temperatures and water uptake of the composite membranes increased in the presence of PIL-SBA-15. The membrane with 6% fillers showed the maximum electrochemical performance with superior mechanical strength. Upon testing this composite membrane as electrolyte in fuel cell using platinum as both anode and cathode electrodes under un-humidified condition, a maximum power density of 183 mW/cm2 was achieved at 140 °C. The existence of additional ion exchange groups (H2PO4−) lead to the improved performance at high temperature.

Incorporating imidazolium-functionalized graphene oxide into imidazolium-functionalized poly(ether ether ketone) for enhanced hydroxide conductivity

The enhancement of hydroxide conductivity in anion exchange membrane fuel cells is of great urgency. Incorporation of fillers with abundant ion exchange groups into polymer electrolyte offers availability to robust membranes with improved ion conductivity. In this study, imidazolium-functionalized graphene oxide (ImGO) was prepared by polydopamine coating on the pristine graphene oxide sheets and subsequent reaction with imidazolium. Then, the ImGO was incorporated into imidazolium-functionalized poly(ether ether ketone) (ImPEEK) matrix to fabricate ImPEEK/ImGO hybrid membranes. Benefiting from the abundant imidazolium groups on ImPEEK and ImGO, the ImPEEK/ImGO hybrid membrane possesses a high ion exchange capacity up to 2.59 mmol g−1 with a moderate water uptake and good mechanical strength simultaneously. The interconnected hydrogen-bonded networks formed between the functional groups and the absorbed water contribute to the maximum hydroxide conductivity of 0.14 S cm−1 at 70 °C and 100% RH at the ImGO loading content of 4 wt%. The ImPEEK/ImGO-4 hybrid membrane shows an improved fuel cell performance with the power density of 50.04 mW cm−2 at 50 °C which is 122% higher than that of the pristine ImPEEK membrane. Moreover, the alkaline and thermal stability of the hybrid membranes are also enhanced.

Synthesis and physico-chemical characterization of cellulose/HO7Sb3 nanocomposite as adsorbent for the removal of some radionuclides from aqueous solutions

Novel organic–inorganic nanocomposite cellulose/HO7Sb3 was prepared chemically by sol–gel mixing of organic poly cellulose into inorganic Sb(OH)5. The prepared nanocomposite was used as an adsorbent for the adsorption of La (III), Co (II) and Cs (I) from aqueous solutions. The adsorbent was characterized by XRD, FTIR, TEM, SEM and TGA. TEM analysis of cellulose/HO7Sb3 shows some dispersed HO7Sb3 particles in the cellulose matrix; having spherical shapes with different sizes with average particle size less than 21 nm. Furthermore, XRD and FTIR analysis confirm the formation of HO7Sb3 structure on poly-crystalline cellulose. The synthesized cellulose/HO7Sb3 demonstrated bifunctional ion-exchange groups (C–OH and Sb–OH) appearing in the FTIR absorption bands at about 1061 and 560 cm−1, respectively. The impacts of various adsorption parameters such as contact time, pH, initial metal concentrations, the amount of cellulose/HO7Sb3 nanoparticles, competing ions and complexing agent and reaction temperature were investigated using batch adsorption experiments. In terms of saturation capacity, this hybrid material retained about 80.05% of the initial saturation capacity when it irradiated by γ-radiation with dose = 50 kGy, at 150 kGy, sharp capacity loss (~ 96%) was observed. Cellulose/HO7Sb3 exhibits selectivity for La (III), Co (II) and Cs (I) in the order of La3+ > Co2+ > Cs+. The changes in the values of free energy (ΔG°) and enthalpy (ΔH°) indicate the spontaneous, feasible and endothermic nature of the sorption process. Radiometric data shows high removal and decontamination efficiency of the prepared nanocomposite especially for La-140 and Co-60. While, Cs-137 removal is less than the other radionuclides.

Removal of hazardous pollutants using bifunctional hydrogel obtained from modified starch by grafting copolymerization

The removal of industrial pollutants from wastewater is important to protect human health and the environment. For this reason, bifunctional hydrogel was synthesized by radiation-induced grafting copolymerization of 2-acrylamido-2-methylpropane-1-sulphonic acid (AMPS) and dimethylaminoethyl methacrylate (DMAEMA) onto starch and subsequent chemical modification of the prepared hydrogel by benzyl chloride. The physical and chemical properties of the hydrogel AMPS co DMAEMA modified with ion-exchange groups were investigated by FT-IR, DSC and SEM techniques. The modified copolymers were examined for the removal of basic dyes, cobalt ions, and phosphate anions from aqueous solution. The maximum adsorption capacities of dye, cobalt and phosphate ions were 600 mg/g, 350 mg/g, and 650 mg/g, respectively at the optimum conditions. The adsorption of dye, Co2+ ions, and phosphate anions onto the hydrogel obeyed both Langmuir and Freundlich models. The adsorption kinetics of dye was found to follow closely the pseudo-first-order kinetic model rather than the pseudo-second-order kinetic model. The kinetic study of Co2+ ions adsorption indicates that it obeys pseudo-second-order kinetic model rather than pseudo-first order one.