Preparation of styrene-based, magnetic polymer microspheres by a swelling and penetration process

A swelling and penetration process is proposed to prepare magnetic polymer microspheres. Micron-size polystyrene (PS) particles were swollen in an aqueous solution of N-methyl-2-pyrrolidone (NMP) and then mixed with superparamagnetic iron oxide nanoparticles. The magnetic nanoparticles were able to diffuse into polymer microspheres and were entrapped within the polymer microspheres. The saturation magnetization of resultant magnetic polymer microspheres increased as increasing magnetic nanoparticle concentrations were added to the swelling mixture. A higher ratio of NMP-to-water led to a greater swelling but a larger loss of polymer mass due to polymer chain dissolution in the NMP solution. Sodium dodecyl sulfate (SDS) in the NMP aqueous solution significantly enhanced the swelling and penetration process. The use of SDS could not only shorten the process time but also lower the required NMP concentration. The proposed method also worked well in preparing magnetic polymers microspheres with other styrene-based copolymer beads like poly(styrene–glycidyl methacrylate) (PS–GMA).     

Synthesis and characterization of air‐stable magnetic Fe composites microspheres of narrow size distribution

Air‐stable Fe magnetic nanoparticles entrapped within carbon and porous crosslinked polystyrene microspheres of narrow size distribution were prepared by the following sequential steps: (1) Polystyrene/poly(divinyl benzene) and polystyrene/poly(styrene‐divinyl benzene) uniform micrometer‐sized composite particles were prepared by a single‐step swelling of uniform polystyrene template microspheres dispersed in an aqueous continuous phase with emulsion droplets of dibutyl phthalate containing the monomers divinyl benzene and styrene and the initiator benzoyl peroxide. The monomers within the swollen polystyrene template microspheres were then polymerized by raising the temperature to 73°C; (2) Porous poly (divinyl benzene) and poly(styrene‐divinyl benzene) uniform crosslinked microspheres were prepared by dissolution of the polystyrene template part of the former composite particles; (3) Uniform magnetic poly(divinyl benzene)/Fe and poly(styrene‐divinyl benzene)/Fe composite microspheres were prepared by entrapping Fe(CO)₅ within the porous crosslinked microspheres, by suction of the Fe complex into the dried porous particles, followed by decomposition of the encapsulated Fe(CO)₅ at 200°C in Ar atmosphere; (4) Uniform magnetic air‐stable C/Fe composite microspheres were prepared similarly, apart from changing the decomposition temperature from 200 to 600°C. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Preparation of magnetic ion‐exchange resins by the suspension polymerization of styrene with magnetite

Magnetic polymer microspheres composed of magnetite, styrene, and divinylbenzene were prepared by suspension polymerization to produce magnetic ion‐exchange resins (MIEXs). The magnetite was grafted with oleic acid to improve the magnetic properties of the MIEXs and to prevent the magnetite from flushing out of the MIEXs. The shape and magnetic properties of the magnetic microspheres were investigated with scanning electron microscopy and vibrating‐sample magnetometry. The average diameter of the prepared magnetic polymer microspheres was about 219 μm. The two types of MIEXs were prepared, magnetic cation‐exchange resins (MCEXs) and magnetic anion‐exchange resins (MAEXs). MCEX was prepared by sulfonation of magnetic polymer microspheres, and MAEX was made by a quaternization reaction with triethylamine of chloromethylated magnetic polymer microspheres. With diffuse‐reflectance Fourier transform infrared spectroscopy, elemental analysis, and acid–base titration, the degree of substitution and ion‐exchange capacity of the MIEXs were assessed. The efficiency of each MCEX and MAEX for the purification of contaminated water was examined with Co²⁺ and NO solutions, respectively. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2058–2067, 2003     

Batch and column adsorption of perfluorooctane sulfonate on anion exchange resins and granular activated carbon

Perfluorooctane sulfonate (PFOS) has been detected widely in the natural water matrix and is persistent, bioaccumulative, and toxic. To prevent the adverse effects of PFOS contamination on human health and the environment, effective removal techniques are needed. Adsorption is considered an effective technique for PFOS removal. In this study, five anion exchange resins and granular activated carbon (GAC) were examined to evaluate their performance for the removal of PFOS in both batch and column experiments. Experimental adsorption data for all of the adsorbents exhibited a high correlation with the Freundlich isotherm (R² = 0.95 – 0.98). Most of the anion exchange resins demonstrated a higher adsorption capacity than the GAC. PFA300 had the highest adsorption capacity (455 mg/g). Continuous adsorption of PFOS was performed in column experiments using the same adsorbents that had been used in the batch experiments. The experimental breakthrough curves were set at C/C₀ = 0.1. PFA300 showed the longest operation time before reaching the breakthrough point. The Yoon and Nelson model was used to predict the half‐saturation time of the anion exchange resins. Moreover, the anion exchange resins exhibited high recovery of PFOS by an organic solvent. Continuous PFOS adsorption on a column can be achieved using anion exchange resins for water/wastewater treatment. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39782.     

A physical route to porous ethyl cellulose microspheres loaded with TiO2 nanoparticles

Porous ethyl cellulose (EC) microspheres were prepared via a physical method in oil‐in‐water (O/W) emulsions. The morphologies and pore structures of the resulting porous microspheres were investigated by scanning electron microscopy (SEM), mercury porosimeter and spectrometer equipped with an integrating sphere. The increase of EC amount in oil phase will increase the size of the microspheres. All the microspheres possess open macropores in the shell and interconnected pores inside the microspheres by means of phase separation. The saturation of the Ethyl acetate (EA) in external phase has an effect on the morphology of the EC particles obtained. Using EA unsaturated aqueous solution as the external water phase in the emulsion process results in the formation of porous EC particles with irregular shape. The loaded TiO₂ nanoparticles uniformly disperse in EC matrix, and slightly deceases the size and volume of interconnected pores inside the microspheres. The addition of TiO₂ nanoparticles is also proved to increase the light‐scattering power of the porous EC microspheres. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40822.     

Synthesis and studies on core–shell type anion exchange resins based on a hybrid polymeric support

In pursuit for new materials for recovery of noble metals, novel anion exchangers, based on new type of core–shell polymeric supports have been synthesized. The designed matrices, with reactive chloromethyl groups concentrated on a surface of the polymeric base, the Amberlite XAD‐4 adsorbent, have been modified using ethylenediamine and polyethyleneimine. The obtained ion exchangers were employed in processes of sorption of gold, platinum, and palladium chlorocomplexes, then, they were compared to similar resins based on volumetric polymeric supports. The studies covered porosity measurements, determination of sorption behavior in the presence of counter ions as well as kinetic and column studies. Ultimately, an attempt to access a core–shell character of the resins has been made using digital‐optical microscopy. The proceeded analyses allowed to determine the localization of the resins’ functionalities and their advantages over traditional ion exchange resins. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43841.     

Synthesis,characterization, and application of new low‐cost ion exchangers

This paper represents a simple method for preparing and characterizing of low‐cost ion exchangers of sulfonated carbon prepared from Terminalia Chebula‐Retz., (family–combretaceae) as a source of cheap plant material blended with phenol‐formaldehyde as a crosslinking agent. The prepared ion exchange resins (IERs) are characterized by infrared (IR) spectral and thermal studies. All the important physicochemical properties of the ion exchangers have been determined. The synthesized resins have cation exchange capacity upto 1.84 mmol g^?1. The rational thermodynamic equilibrium constant (ln K) are calculated for H⁺ and Zn²⁺ exchanges on the resin having various amount of sulfonated Terminalia Chebula Retz. carbon (STCC). The thermodynamic parameters were calculated, and suitable explanations are given. It is concluded from the present study that PFR sample could be blended with 20% (w/w) of STCC, without affecting its physicochemical, spectral, and thermal properties. Hence blending with STCC will definitely lower the cost of the ion exchange resin. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4104–4113, 2006     

Preparation,characterization, and drug‐release properties of poly(N‐isopropylacrylamide) microspheres having poly(itaconic acid) graft chains

An inverse suspension polymerization method for the preparation of thermoresponsive hydrogel microspheres based on N‐isopropylacrylamide was described in this article. The polymerization reaction was carried out at 200 rpm stirring rate and the microspheres obtained were in the size range of 71–500 μm in the swollen states. The particles were sieved by using ASTM sieves. The selected fraction (180–250 μm) of poly(N‐isopropylacrylamide) (PNIPAAm) microspheres was used for radiation‐induced modification with itaconic acid (IA) to obtain PNIPAAm/poly(itaconic acid) graft copolymer. Viagra and lidocaine were used as model drugs for the investigation of controlled‐release behavior of the microspheres. Incorporation of IA graft chains onto microspheres enhanced significantly the uptake of both drugs and further controlled release at specific pH values. The release studies showed that some of the basic parameters affecting the drug‐loading and ‐release behavior of the microspheres were pH, temperature, particle size, and chemical nature of drug. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1115–1124, 2005     

Preparation and catalytic properties of composites with palladium nanoparticles and poly(methacrylic acid) microspheres

Palladium (Pd) nanoparticles with different sizes are in situ synthesized by reduction of PdCl₂ with NaBH₄ as reductant in the presence of poly(methacrylic acid) (PMAA)microspheres. The obtained PMAA/Pd composites are characterized by Fourier transform infrared spectra, X‐ray diffraction, and Transmission electron microscopy. The catalytic activity of the PMAA/Pd composites is investigated using a model reaction, that is, reduction of p‐nitrophenol to p‐aminophenol. The reaction shows first‐order kinetics, and the reaction rate increases with increasing reaction temperature, p‐nitrophenol concentration, and loadings of Pd nanoparticles on PMAA microspheres. The PMAA/Pd composites exhibit good stability, ascribing to the Pd nanoparticles stabilized by PMAA microspheres. POLYM. COMPOS., 35:2251–2260, 2014. © 2014 Society of Plastics Engineers     

Retention of gallium ions from acidic solutions by pyridine strong‐base anion exchangers

Using the batch method, the retention of Ga(III) from HCl solutions by two gel‐type pyridine strong‐base anion exchangers containing 1‐methyl‐ or 1‐butyl‐4‐vinylpyridinium chloride structural units, called S₁ and S₂ resins, respectively, was studied. The influence of the HCl and Ga(III) concentrations as well as of the contact time between the resin and the liquid phase was investigated. The parameters, which characterize the retention process, were estimated using Langmuir and Freundlich isotherms. Both resins exhibited a higher affinity for gallium ions from a 6M HCl solution. According to Langmuir isotherms, maximum retention capacities of 44.44 and 60 mg Ga(III)/g dry resin for the S₁ and S₂ resins, respectively, were obtained. Freundlich isotherms provide additional proof for a higher affinity of the S₂ resin for Ga(III) from HCl solutions. It is clear that the substituent length increase on N⁺ atoms led to an increasing affinity of the pyridine strong base anion exchangers toward Ga(III). © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3440–3444, 2002     

The Coagulation of Finely-Divided Ion Exchange Resins and the Use of the Coagulated Material for Rapid Ion Removal

Abstract

Finely-ground ion exchange resin particles remove ions from solution much more rapidly than the conventional-size beads. Such finely-divided solids form suspensions when added to aqueous solutions. A method was required for rapidly removing such suspensions once ion adsorption had occurred, and to this end it is shown that the particles (-400 mesh) can be completely coagulated within a few minutes by the addition of suspensions of oppositely-charged solids. Thus anion exchange resins are coagulated by cation exchange resins (200 to 400), montmorillonite (200), kaolin (30), charcoal (10), silica (10), and glass (5), the figures representing arbitrarily defined relative coagulating abilities. Coagulating power is shown to increase markedly with decreasing particle size. Most suitable for ion removal is a mixed finely-divided resin formed by coagulation of anionic and cationic resins from pure water. The mixed resin, when added to 1 liter of 3 × 10^?4 M sodium phosphate solution removes all the phosphorus within 2 min, and when added to 1 liter of 2.5 × 10^?4 M calcium chloride, removes over 90% of the calcium within 3 min.     

α‐Amylase immobilized by Fe3O4/poly(styrene‐co‐maleic anhydride) magnetic composite microspheres: Preparation and characterization

Fe₃O₄/poly(styrene‐co‐maleic anhydride) core–shell composite microspheres, suitable for binding enzymes, were prepared using magnetite particles as seeds by copolymerization of styrene and maleic anhydride. The magnetite particles were encapsulated by polyethylene glycol, which improved the affinity between the magnetite particles and the monomers, thus showing that the size of the microspheres, the amount of the surface anhydrides, and the magnetite content in the composite are highly dependent on magnetite particles, comonomer ratio, and dispersion medium used in the polymerization. The composite microspheres, having 0.08–0.8 μm diameter and containing 100–800 μg magnetite/g microspheres and 0–18 mmol surface‐anhydride groups/g microsphere, were obtained. Free α‐amylase was immobilized on the microspheres containing reactive surface‐anhydride groups by covalent binding. The effects of immobilization on the properties of the immobilized α‐amylase [magnetic immobilized enzyme (MIE)] were studied. The activity of MIE and protein binding capacity reached 113,800 U and 544.3 mg/g dry microspheres, respectively. The activity recovery was 47.2%. The MIE had higher optimum temperature and pH compared with those of free α‐amylase and showed excellent thermal, storage, pH, and operational stability. Furthermore, it can be easily separated in a magnetic field and reused repeatedly. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 328–335, 2005     

Quaternized biomass as an anion exchanger for the removal of nitrate and other anions from water

Dried Chinese Reed (Miscanthus sinensis), a fast growing plant, was used as a model biomass for the development of anion exchangers using a quaternization agent, N‐(3‐chloro‐2‐hydroxypropyl)trimethylammonium chloride (CHMAC), and a cross‐linking agent, epichlorohydrin. Anions studied include nitrate, phosphate, perchlorate and sulfate. Batch mode adsorption studies were conducted using aqueous solutions of anions. Detailed kinetics were studied for nitrate removal. Parameters studied included anion concentration, agitation time, adsorbent dose, and pH. Adsorption equilibrium occurred in 10 min for all the anions studied. Equilibrium adsorption data followed both Langmuir and Freundlich isotherms. The presence of phosphate, perchlorate, fluoride and sulfate lowered the adsorption significantly. The effects of pH on adsorption and desorption show that ion exchange is involved in the adsorption process. The adsorption capacity of the cross‐linked and quaternized Chinese Reed for nitrate, sulfate, phosphate and perchlorate was found to be 7.55, 13.25, 16.61 and 10.07 mg of anion per g of the anion exchanger, respectively. Copyright © 2004 Society of Chemical Industry     

Synthesis,characterization, and bactericidal properties of composites based on crosslinked resins containing silver

Two different commercial crosslinked resins (Amberlite GT73 and Amberlite IRC748) were employed for anchoring silver. The ? SH and ? N(CH₂COOH)₂ groups, respectively, present on these resins were used for Ag⁺ chelation from an aqueous solution. The Ag⁺ ions were reduced with three different reductants: hydrazine, hydroxylamine, and formaldehyde (under an alkaline pH). The produced composites were characterized with thermogravimetry/differential thermogravimetry and scanning electron microscopy combined with a backscattered scanning electron detector. Energy‐dispersive X‐ray spectroscopy coupled to scanning electron microscopy allowed the observation of submicrometer particles of silver, and chemical microanalysis of emitted X‐rays revealed the presence of metal on the internal and external surfaces of the composite microspheres. The amount of incorporated silver was determined by titration. The antibacterial activity of the silver/resin composites was determined toward 10³–10⁷ cells/mL dilutions of the auxotrophic AB1157 Escherichia coli strain; the networks containing anchored submicrometer silver particles were completely bactericidal within a few minutes because of the combined action of silver and functional groups of the resins. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Preparation of thiourea functionalized polyvinyl alcohol‐coated magnetic nanoparticles and their application in Pb2+ ions adsorption

We have prepared a novel kind of magnetic nanoparticle with high adsorption capacity and good selectivity for Pb²⁺ ions by modifying the magnetic nanoparticles with polyvinyl alcohol (PVA) and thiourea. The resultant magnetic nanoparticles were used to adsorb Pb²⁺ ions from aqueous solution. The influence of the solution pH, the adsorption time, the adsorption temperature, coexisting ions, and the initial concentration of Pb²⁺ ions on the adsorption of Pb²⁺ ions were investigated. The results indicated that Pb²⁺ ions adsorption was an endothermic reaction, and adsorption equilibrium was achieved within 30 min. The optimal pH for the adsorption of Pb²⁺ ions was pH 5.5, and the maximum adsorption capacity of Pb²⁺ ions was found to be 220 mg/g. Moreover, the coexisting cations such as Ca²⁺, Co²⁺, and Ni²⁺ had little effect on adsorption of Pb²⁺ ions. The regeneration studies showed that thiourea functionalized PVA‐coated magnetic nanoparticles could be reused for the adsorption of Pb²⁺ ions from aqueous solutions over five cycles without remarkable change in the adsorption capacity. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40777.     

Preparation and characterization of chitosan-poly(acrylic acid) polymer magnetic microspheres

A modified method to prepare chitosan-poly(acrylic acid)(CS-PAA) polymer magnetic microspheres was reported in this paper. First, via self-assembly of positively charged CS and negatively charged Fe₃O₄ nanoparticles, magnetic CS cores with a large amount of Fe₃O₄ nanoparticles were successfully prepared. Subsequently, the AA monomers were polymerized on the magetic CS cores based on the reaction system of water-soluble polymer-monomer pairs. These polymer magnetic microspheres had a high Fe₃O₄ loading content, and showed unique pH-dependent behaviors on the size and zeta potential. From the magnetometer measurements data, the CS-PAA polymer magnetic microspheres also had superparamagnetic property as well as fast magnetic response. A continuous release of the entrapped ammonium glycyrrhizinate in such polymer magnetic microspheres occurred, which confirmed the potential applications of these microspheres for the targeted delivery of drugs.     

Sorption of aromatic compounds on macroporous anion exchangers based on polyacrylamide: Relation between structure and sorption behavior

The sorption of phenol, p-toluenesulfonic acid (p-TSA), Na-p-toluenesulfonate (Na-p-TS), 1,2-dihydroxy-3,5-benzene disulfonic acid disodium salt (Tiron), and 3-hydroxy-4(sulfonaphthyazo)-5,7-naphthalenedisulfonic acid trisodium salt (Poceau 4R) on the macroporus anion exchangers with acrylamide structural units (weak and strong basic anion exchangers) and on the ion exchangers with amidoxime groups were studied. The maximum specific sorption of p-TSA was almost identical with the total exchange capacity for both the weak and strong basic anion exchangers. The sorption of Na-p-TS is strongly related to the functional group structure of the anion exchangers, being significant on the strong basic anion excahngers. The maximum specific sorption of Tiron was higher tan the total exchange capacity of the strong basic anion exchangers because it is mainly dependent on the ionic exchange properties. The morphological characteristics influenced only the establishement rate of the sorption equilibrium. The sorption of Ponceau 4R, which has the highest molecular weight, is important on the strong basic anion exchangers with high permanent porosity. The sorption of the organic anions is also dependent on the number of the sulfonic groups. © 1995 John Wiley & Sons, Inc.     

Elasticity of ion‐exchange resin beads in solvent mixtures

The effect of the solvent composition on the elasticity of strong and weak cation‐ and anion‐exchange resin beads was studied. Poly(styrene‐co‐divinylbenzene) resins containing sulfonic acid or quaternary ammonium groups and an acrylic acid resin crosslinked with divinylbenzene were immersed in water, NaCl solutions, or aqueous alcohol solutions and the shear modulus was measured with a uniaxial compression method. The elastic data were compared with the swelling properties. In pure water the shear moduli increased when the crosslink density, counterion valence, counterion size, and functional group size increased. Two additional phenomena in the elastic behavior were observed when the swelling degree of the resins was changed by the addition of alcohol or salt. A decrease of the modulus was observed when moving from the fully swollen state to a less swollen state, and a steep upturn of the modulus took place at a characteristic swelling region. The depth of the minimum and the location of the transition from the rubbery to the glassy state depended on the characteristics of the resins. The finite expansibility of the polymer chains and the glass transition explained these findings. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1256–1264, 2001     

Synthesis and properties of novel phenolic resins modified with nanosized copper particles

Phenol–formaldehyde (PF) resins modified with nanosized copper particles were synthesized by an in situ polymerization process. X‐ray diffraction analysis and transmission electron microscopy revealed that the copper particles in the resulting PF resins had a spherical geometry with a size of 30–60 nm in diameter, and there were about 5% of the particles which were agglomerated. The thermal properties of the resulting PF resins were investigated using TGA. It was found that the copper nanoparticles markedly improved the thermal stability of the PF resins at lower temperatures. The initial decomposition temperature of the modified PF resins could be increased by 47 °C compared to unmodified resins. However, the copper nanoparticles increased the rate of degradation of the PF resins at elevated temperatures. The effects of copper nanoparticles on the thermal properties of the PF resins when used as binders for friction materials are beneficial. The toughness of the resulting PF resins was also studied. The results revealed that copper nanoparticles obviously improved the brittleness of the PF resins. The impact strength of the modified PF resins was increased by 66.6% compared to unmodified resins. Copyright © 2006 Society of Chemical Industry     

An anion exchange resin from soybean hulls

Agricultural by‐products are generally poor adsorbents of anions in solution. Therefore, modification of the by‐product could enhance its anion exchange capabilities. The objective of this study was to increase the anion exchange properties of the agricultural by‐product, soybean hulls, by chemical modification. Soybean hulls were quaternized with the quaternizing agent, N‐(3‐chloro‐2‐hydroxypropyl) trimethylammonium chloride, in the presence of a strongly alkaline environment. This modification increased the amount of positive charge on the hulls as evidenced by increased nitrogen content and increased uptake of anions compared with the unmodified hulls. A method to optimize the anion exchange properties of the hulls was developed. Ion exchange properties of the hulls toward anions of environmental significance, namely arsenate (As), chromate (Cr), dichromate (Cr₂), phosphate (P) and selenate (Se) were determined. The modified hulls were also compared with commercial cellulose‐based and synthetic anion exchange resins in their ability to remove these anions from solution. The experimental and commercial resins were also compared for their ability to remove a mixture of arsenate, chromate, dichromate and selenate from laboratory prepared solutions to levels below the maximum contaminant levels for these anions in drinking water as specified by the US Environmental Protection Agency (US EPA). Our results demonstrate that the soy hull resin is more efficient in anion removal than the commercial cellulose‐based resin but not as effective as the commercial synthetic resin. Published in 2003 for SCI by John Wiley & Sons, Ltd.