Cr(VI)‐containing wastewater treatment by means of ion exchange on weak‐ and strong‐base anion exchangers

The aim of this research work was a thermodynamic and kinetic study of the retention of Cr(VI) ions from a K₂CrO₄ solution on macroporous weak‐ and strong‐base anion exchangers, Lewatit M 64 A and Lewatit MP 500 A, respectively. Also, the correlations among the ion‐exchange rate, the retention capacity of Cr(VI), and some process parameters were established. The parameters studied mainly were the concentration of Cr(VI) ions and the type of the counterions coupled with active groups from the anion exchangers. The results led to the conclusion that, for the Lewatit M 64 A resin, there is the following order of the Cr(VI) retention capacity: RCl > R₂SO₄ > ROH, while for the strong‐base anion exchanger, the retention capacity for the Cr(VI) ions is different: ROH > RCl > R₂SO₄. In the Cl^? form, both anion exchangers have the same retention‐capacity values. On the other side, the weak‐base anion exchanger in SO and OH^? forms presents the lowest retention‐capacity values. The process kinetics also presents some differences: for the Lewatit M 64 A resin, the ion‐exchange rate has lower values, especially in the OH^? form. This result is attributed to the increase of the OH^? ion concentration in the solution and its presence hinders the dissociation of the active groups of a weak‐base anion exchanger. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2093–2098, 2002     

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     

Column adsorption of chromium(VI) by strong alkaline anion‐exchange fiber

The removal of chromium(VI) from saturated sodium chloride (NaCl) solution by strong alkaline anion‐exchange fiber (SAAEF) was achieved with column experiments. Factors affecting the adsorption, such as the pH value, loading density, flow rate, and operational temperature, were investigated. The results show that Cr(VI) removal was remarkably pH dependent. The optimal operational conditions were as follows: pH value = 2.0, loading density = 0.12–0.19 g/cm³, room temperature, and flow rate = 6–12 BV/h. The SAAEF column could be regenerated completely by 2% NaOH in saturated NaCl or 2% KOH in 15% KCl as an eluent. Cr(VI) was recycled as Na₂Cr₂O₇ and K₂Cr₂O₇, respectively. The desorption rate of Cr(VI) reached 98.09%. The adsorption ability of the SAAEFs was stable after repeated use. Overall, the results indicate that SAAEF proved to be an effective material for the adsorption of high concentrations of Cr(VI) from a saturated NaCl solution. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Sorption of Cr(III)‐containing cations on strongly basic anion exchangers

It is shown that strongly basic anion exchangers AV‐17 and Varion‐AD in definite conditions are able to retain Cr(III)‐containing ions from Cr(III) sulfate solution. It is found that the sorption of Cr(III)‐containing ions on the polymers is essentially dependent on the pH, temperature, and Cr(III) sulfate concentration. The maximum temperature dependence of sorption was found to be about 60°C. The sorption isotherms are well described by Langmuir's equations. The sorption kinetics is determined by the diffusion of Cr(III)‐containing ions into polymer's phase. It is assumed that the Cr(III)‐containing ions are retained through formation, in polymer's phase, of the jarosite‐type mineral compounds: R₄N[Cr₃(OH)₆(SO₄)₂], H₃O[Cr₃(OH)₆(SO₄)₂], and K[Cr₃(OH)₆(SO₄)₂]. For comparison of sorptional capacities, the sorption of Cr(III)‐containing ions was determined on different cation and anion exchangers. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3978–3985, 2006     

Acrylic weak‐base anion exchangers and their behaviors in the retention process of some heavy‐metal cations

Two macroporous acrylonitrile/10% vinyl acetate/10% divinylbenzene copolymers as beads were obtained by the aqueous suspension copolymerization of the three comonomers in the presence of toluene as a diluent, which was used in two different amounts. These copolymers were chemically modified by their reactions with ethylenediamine, diethylenetriamine, and triethylenetetramine in the presence of water when the aminolysis–hydrolysis reaction of the nitrile groups and the hydrolysis reaction of the acetate groups occurred. From these reactions, weak‐base anion exchangers with high ion‐exchange capacities, between 1.6 and 2.2 mequiv/mL and 6.5 and 10.5 mequiv/g, were obtained. For these anion exchangers, the behaviors in the retention processes of the Ni(II), Cd(II), and Pb(II) cations were evaluated with the bath method. All the resins exhibited retention properties, but the retained amounts of the metal cations differed as a function of the resin and cation nature. Thus, the resin from the reaction with triethylenetetramine of the copolymer obtained in the presence of a larger amount of toluene could be considered the most suitable sorbent for the three metal cations, especially for Ni(II). Its maximum retention capacity for this cation was 2.67 mequiv/g of dried resin. From the noncompetitive and competitive retentions was observed the following selectivity order: Ni(II) > Cd(II) > Pb(II). The retention took place by the chelating processes between the functional groups with the ligand role, especially free amine groups, and metal cations. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 930–938, 2005     

Adsorption of Zn(II) by crosslinked acrylic copolymers with amine functional groups

Adsorption of Zn(II) ions from diluted aqueous solutions by the acrylic copolymer based on ethylacrylate : acrylonitrile : divinylbenzene matrix with different crosslinking degrees and ethylenediamine and triethylenetetramine functional groups was investigated. Adsorption experiments were carried out by batch method. The effects of the pH, initial concentration of zinc, time of contact, and the crosslinking degree of the copolymers were studied. On the basis of Langmuir and Freundlich isotherms, the parameters that characterize the adsorption were determined. The maximum Zn(II) retention capacity value (500 mg g^?1) was obtained for the acrylic copolymer with 2% crosslinking degree and ethylenediamine, as functional groups. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 803–808, 2004     

Competitive adsorption of uranyl ions in the presence of Pb(II) and Cd(II) ions by poly(glycidyl methacrylate) microbeads carrying amidoxime groups and polarographic determination

The adsorption capacity of UO in the presence of Pb(II) and Cd(II) ions was investigated with amidoximated poly(glycidyl methacrylate) (PGMA) microbeads with an average size of 135 μm packed in a glass column (0.5‐cm i.d. and 20‐cm length, flow rate = 3 mL/min) under competitive conditions. A differential pulse polarography technique was used for the determination of trace quantities of uptaken elements by the measurement of the reduction peak currents at ?200/?950, ?400, and ?600 mV (vs a saturated calomel electrode) for UO, Pb(II), and Cd(II) ions, respectively. When only UO was found in the eluate, its adsorption was 85.3% from a 50 μM initial solution. However, when there was UO with binary systems of Pb(II) or Cd(II), it was 78.2 and 76.3%, respectively. On the other hand, in a ternary mixture of UO with Pb(II) and Cd(II), the adsorption was found to be 75.2% with the same initial concentration. According to the results, the competitive adsorption studies showed that these amidoximated PGMA microbeads had good adsorption selectivity for UO with the coexistence of Pb(II) and Cd(II) ions. The ionic strength of the solution also influenced the UO adsorption capacity of the amidoximated PGMA microbeads. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 4168–4172, 2007     

Metal coordination and selectivity with oxine ligands bound to silica polyamine composites

A series of oxine ligands, 5‐X, 8? OH? C₉H₆N (X = H, Cl, SO₃H) have been covalently bound to a silica gel polyamine composite made from a silanized amorphous silica xerogel and poly(allylamine) (BP‐1) by the Mannich reaction. The resulting modified composites WP‐4(X = H), CB‐1(X = Cl), and SB‐1(X = SO₃H) were characterized by elemental analysis, FTIR, and solid state CPMAS‐¹³C‐NMR. Using the analytical data before and after the ligand modification, the ligand loading could be estimated and in combination with metal ion capacities a metal to ligand ratio could be obtained. The composites WP‐4 and CB‐1 both showed ratios of approximately 1 : 1 while the sulfonate modified composite, SB‐1, showed a metal to ligand ratio of 1 : 2. This is tentatively interpreted in terms of a zwitterionic oxine as the dominant species at pH = 2 where the sulfonic acid group is ionized, the quinoline nitrogen is protonated and where two sulfonate groups on adjacent oxines bind a trivalent or divalent ion. All the modified composites show a clear selectivity for trivalent over divalent ions and a good selectivity for gallium over aluminum. The substituent groups on the oxine ligand have only a minor influence on these selectivity trends but SB‐1 shows slightly better capture kinetics. The selectivity for gallium over aluminum is applied to the separation of gallium from aluminum, ferrous, and zinc in an acid ore leach of solid tailings obtained from a zinc mine using WP‐4. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Production of microporous resins for heavy‐metal removal. II. Functionalized polymers

Ion‐exchange polymers were used successfully in water‐treatment operations. In this study, three ion‐exchange resins based on 4‐vinylpyridine and divinylbenzene functionalized with N‐oxide groups were obtained. Their ion‐adsorption properties were measured in solutions containing chromium at concentrations of 4 and 500 ppm with column and batch equilibrium techniques. The removal efficiency of the chromium ions with HCl was observed to increase after the protonation of the N‐oxide groups. The resins could be reused after 10 cycles with the metal removal efficiency maintained at higher than 95%. These studies evidenced a strong correlation between the morphology and ionic group content in the resin and its chromium ion sorption capability. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

A mild and clean synthesis of alkyl azides from alkyl halides mediated by poly(4‐vinylpyridine)‐supported sodium azide under nonaqueous conditions

Alkyl halides were efficiently converted to their corresponding alkyl azides under mild nonaqueous conditions with a polymer‐supported azide as a new polymeric reagent at room temperature at high yields and purities. All of the byproducts were removed by filtration, and pure products were obtained by the evaporation of the solvent. The spent polymeric reagent could usually be removed quantitatively and regenerated. The regenerated polymeric reagent could be reused several times. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Sorption of heavy metal ions from aqueous solutions in the presence of EDTA on monodisperse anion exchangers

Conventional precipitation methods of industrial sewage and wastewater purification are not very effective and are insufficient in many cases. This implies the necessity of searching new, effective methods exploiting cheap, accessible and ecologically safe ion exchangers and sorbents. The paper presents the studies on removal of heavy metal ions — Cu(II), Zn(II), Co(II), Ni(II) and Fe(III) — from aqueous solutions in the presence of EDTA carried out on commercially available, strongly basic monodisperse anion exchangers with the polystyrene skeleton gel, Lewatit MonoPlus M 500; and the macroporous, Lewatit MonoPlus MP 500, which are more widely applied in water purification processes. The research results indicate a high affinity of the Lewatit MonoPlus M 500 and Lewatit MonoPlus MP 500 anion exchangers in the chloride form for copper(II), nickel(II), cobalt(II) and zinc(II) complexes with EDTA. The affinity series for the heavy metal complexes in the 0.001 M M(II)/(III)–0.001 M EDTA and 0.001 M M(II)/(III)–0.001M EDTA–0.001 M–0.002 M NaOH systems were found for the Lewatit MonoPlus M 500 anion exchanger in the chloride form to be as follows: Cu(II) > Ni(II) > Co(II) > Zn(II) Fe(III). In the case of the Lewatit MonoPlus MP 500 anion exchanger in the chloride form there was found the following affinity series: Cu(II) > Co(II) > Ni(II) > Zn(II) Fe(III). These anion exchangers can be applied in the removal of copper(II) complexes from waters and wastewaters.     

Synthesis of chelating polymer sorbents by using the S methodology

The article describes a new synthetic approach to modify the structure of phenol-formaldehyde and resorcinol-formaldehyde resins, which enables one to functionalize a polymer matrix by using the S (nucleophilic aromatic substitution of hydrogen) methodology. Direct heteroarylation of phenol (resorcinol) fragments in polymer chains with 1,2,4-triazine derivatives illustrates a new synthetic method in the polymer chemistry. The feature of this methodology is that it provides an opportunity to accomplish direct one-pot polymer transformations by incorporating of rather complicated chelating groups through the displacement of hydrogen in phenol moieties. It has been shown that in order to obtain chemically modified polymers on the basis of phenol-formaldehyde and resorcinol-formaldehyde resins with a high degree of substitution with chelating units, a polymer matrix has to react with 3-(pyridin-2′-yl)-1,2,4-triazin-5(2H)-one. Also, it has been found that polymer sorbents with a high selectivity can be obtained by using the template method. Targeted synthesis of model compounds, as structural units of the chelating polymers, and elucidation of the structure of their complexes with copper (II) ions have shown that the most plausible type of coordination is formation of the bridge 1 : 1 complexes of the α,α′-bipyridinyl type. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Sorption of palladium (II) chloride complexes on weakly, intermediate and strongly basic anion exchangers

The precious metals and their alloys are extensively applied in refineries and the chemical and electronic industries as well as in medicine. Their small amounts in nature and extensive exploitation from natural resources are a serious obstacle as far as their application is concerned. High prices of palladium favour its recovery from recyclable materials and industrial wastes. Ion-exchange chromatography is one of the physicochemical methods of noble metal ion recovery. A study was done on the possibility of selective removal of palladium (II) microquantities from the model 0.1-6.0 M HCl, 0.1-0.9 M HCl-0.9 - 0.1 M HNO₃, 1.0 M ZnCl₂ - 0.1 M HCl and 1.0 M AlCl₃-0.1 M HCl systems on weakly, intermediate and strongly basic anion exchangers. The sorption research of Pd (II) on various types of anion exchangers was carried out by means of dynamic and static methods. The working ion-exchange capacities, weight and bed distribution coefficients were calculated from the breakthrough curves of palladium (II) ions. From the static studies the recovery factors of Pd (II) depending on the anion exchanger-solution contact time in the model systems under discussion were determined.     

Poly(aryl ether ketone)s with bromomethyl groups: Synthesis and quaternary amination

A series of bromomethylated poly(arylene ether ketone)s (PAEKs) with different contents of bromine tethered to the benzyl groups were successfully synthesized and characterized in this work. For this purpose, poly(arylene ether ketone) with 3,3′,5,5′‐tetramethyl‐4,4′‐dihydroxybipheny moiety (PAEK‐TM) was prepared by the aromatic nucleophilic polycondensation, and then the PAEK‐TM has benzylic methyl groups that were converted to bromomethyl groups by a radical reaction using N‐bromosuccinimide. Then, the bromomethylbenzyl groups in the membrane was converted to quaternary ammonium moieties in TMPAEK‐NOH. ¹H‐NMR measurements were used to characterize and confirm the structures of the resulting PAEK‐x‐BrTM and TMPAEK‐NBr derivatives (x refers to the molar percentage of bromine introduced per repeating units). TGA analysis showed that PAEK‐x‐BrTM exhibited a very low‐decomposition temperature at about 200°C corresponding to the C Br bond cleavage. The hydroxide conductivity of TMPAEK‐NOH membrane was 8 mS cm⁻¹ at room temperature, while the water uptake of TMPAEK‐NOH membrane was 22.3% at 20°C and 32.6% at 60°C. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Unforseen factors influencing Fe(III)‐containing cations sorption on strongly basic anion exchangers

The sorption and partial destruction of the Fe(III)‐containing compounds in the aqueous medium in strongly basic anion exchangers AV‐17 and Varion‐AD phase have been investigated. It is shown that partial destruction of the Fe (III) compounds in acidulated water (pH = 2) and in K₂SO₄, Fe₂(SO₄)₃ solutions takes place. With increasing of temperature up to 50°C, the desorption degree of the iron ions from polymer phase decreases. In dried polymer, the structural and electronic state of iron compounds, according to their magnetic susceptibility, remains stable for a long time. The sorption of the Fe(III)‐containing cations at 50°C during 12 h depends essentially on the sizes of polymer granules. Sorption increases with growing of polymer granules. For comparison of sorptional capacities, the sorption of Fe(III)‐containing cations was determined on different cation and anion exchangers. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Preparation of Cr(VI)-imprinted polypropylene nonwoven fibers using plasma polymerization-assisted grafting

Polypropylene (PP) fibers were grafted with glycidyl methacrylate (GMA) using plasma polymerization and then aminated, imprinted, and crosslinked to prepare Cr(VI)-imprinted fibers. The plasma polymerization conditions were optimized by single factor experiment and response surface methodology, and various properties and adsorption mechanism of the fibers were analyzed. The results showed that at pH 3, the imprinted fibers had a maximum Cr(VI) adsorption capacity of 173.36 mg/g, and the adsorption equilibrium could be reached within 40 min. In the presence of competing ions (SO₄²⁻, NO₃⁻ and PO₄³⁻) each at a concentration of 5 times of that of Cr(VI), the Cr(VI) adsorption rate of the fibers could be maintained at around 50%, which indicates that the imprinted fibers have high selectivity towards Cr(VI). The results also showed that the imprinted fibers had good reusability and enrichment ability, thus can be a good candidate for treating actual Cr(VI)-contaminated water.     

Preparation and characterization of thermosensitive beads with macroporous structures

Thermosensitive copolymers of poly(N‐isopropyl acrylamide)‐co‐2‐hydroxyethyl methacrylate (NIPA‐co‐HEMA) macroporous resins were synthesized in the form of beads by inverse suspension polymerization. The copolymerization was carried out in aqueous solutions of the comonomers dispersed by cyclohexane with stabilizers. A series of resins with different molar ratios of NIPA : HEMA, and different crosslinking degrees was obtained. The compositions of the copolymers were determined by elemental analysis. The results showed that the content of HEMA in a copolymer was higher than that of the corresponding feed mixture from which the copolymer was made. IR spectra also confirmed the structure of the copolymers. The porous parameters such as true densities, apparent densities, pore volumes, and porosities of the resins were measured by means of pycnometry. The determination of equilibrium swelling ratios and measurement of differential scanning calibration indicated that the resins exhibited thermosensitivity in aqueous solutions. Finally, the loading of hydroxyl groups was determined by titration. The resins have potential applications as supports in solid‐phase synthesis after being functionalized. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1792–1797, 2004     

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     

Polyacrylate anion exchangers in sorption of heavy metal ions with non-biodegradable complexing agents

The polyacrylate anion exchangers are widely used in purification of heavy metal ions from wastewaters and different accompanying complexing agents. Such effluents containing the chelators (EDTA, NTA, HEDTA, DTPA, and IDA) are discharged from relevant industries such as printed circuits boards, plating on plastics, metal finishing and others. The sorption was studied as a function of phase contact time and pH by the batch technique. It was found that the removal of heavy metal ions in the presence of EDTA, NTA and IDA strictly depends on the phase contact time and pH values. Various kinetic models such as the pseudo first-order and the pseudo second-order as well as the intraparticle one were also tested to estimate the sorption rate. The equilibrium capacities of the studied anion exchangers for Cu(II), Zn(II), Co(II), Ni(II), Pb(II) and Cd(II) in the presence of EDTA were the highest for Pb(II) and Cd(II). The order of sorption for Amberlite IRA 458, Amberlite IRA 958 as well as Amberlite IRA 67 can be as follows: Pb(II) > Cd(II) > Zn(II) > Cu(II) > Ni(II) > Co(II). The stability of forming complexes was also compared. The estimation of the capacities of anion exchangers under investigation by the continuous column studies was also carried out.     

A simple postsulfonation of poly(arylene ether sulfone) Radel® R

Commercially available Radel® R, a poorly acid resistant biphenol‐based poly(arylene ether sulfone), was successfully sulfonated by a simple and rapid postsulfonation reaction using oleum as the sulfonating agent. Polymer degradation due to contact with acid could easily be minimized by adjusting reaction conditions. The suitable reaction conditions, when the 1 : 3 molar ratio of the polymer to the sulfonating agent was used, were: 10% of oleum in chloroform, 10% concentration of Radel® R in chloroform, and temperature between 0 and 50°C. Under these conditions, the reaction was complete within 45 min. Thermal properties, degradation characteristics and the viscosity of the postsulfonated polymer are reported. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011