Weak Base Anion Exchange Resin Research Articles

Features of Humic Compound Sorption by Anion Exchangers

The removal of humic compounds is an urgent task in tap water treatment in Ukraine. The use of polymeric recycled scavengers is most perspective for the purification of water up to the requirements needed for drinking and technical water. This study shows results for the extraction of the humic compounds from water by strong- and weak-base anion exchange resins with various porous structures. The results show that SDVB-base anion exchange resins Dowex 11, Dowex MSA-1 and Dowex MWA-1 are most effective. Studies were performed by static and dynamic conditions. Mechanism of the adsorption of humic compounds by anion exchange resins and the application for different tasks of water treatment were shown.

Adsorption of CO2 on Composites of Strong and Weak Basic Anion Exchange Resin and Chitosan.

A new method is proposed to improve the adsorption properties of basic, macroreticular (MR) anion exchange resins by forming a material composite with chitosan. In this study, one strong basic and one weak basic MR resins were used as matrixes for the new composites. Chitosan was accumulated in the macropores of the resins, and breakthrough curves for adsorption of CO2 on the new adsorbents were measured. The resulting equilibrium and kinetic data were compared with those of the original resins. The composite of strong basic MR resin and chitosan showed a more than three times higher adsorption capacity for CO2 than the pure resin. On the other hand, the mass transport in the adsorbent slowed down due to a narrowing of the pores by deposited chitosan.

Effect of chemical modifications upon exchange capacity of aminated macroporous styrene-divinyl benzene (PS-DVB) copolymer anion exchange resin

The macroporous PS–DVB resin was prepared in the laboratory by suspension polymerization using gelatin as stabilizer and toluene as porogen. This is subsequently nitrated by a mixture of NO and NO2 (called NOx) in a gas phase reaction, and the carbon–nitrogen covalent bonding has been demonstrated by modified Laissagne spot test, FTIR, and ESCA analysis. This has been aminated by reducing the nitrate groups using hydrazine hydrate, and the resultant weak base anion exchange resin was shown to have a one-time exchange property because of its inability to be regenerated by the usual ASTM procedures. The chloroethylated PS–DVB resin is prepared by reacting aminated resin with dichloroethane, and is shown that two molecules of the latter react with every amine group. The regenerable strong-base anion exchange resin is then prepared by quarternizing it with tartiary (trimethyl and triethyl) amines and triphenyl phosphine, and it is shown that these gegen ions have a considerable effect on the exchange ability of the resin. We have found the duration of nitration to be the most important parameter affecting the capacity, and in this work, we report studies for all these gegen ions. It is found that for any gegen ion, the exchange capacity first increases for short times of nitration, reaches a broad maxima of around 5 mEq/g of wet resin with about 69% moisture content (or 15.48 mEq/dry g), and falls slightly for larger times of nitration due to a slight degradation. This is to be compared with commercial chloromethylated resin, which has an exchange capacity of 1.68 mEq/g of wet resin with 43.53% moisture content (or 2.97 mEq/dry g of resin). It is found that the resin with triphenyl phosphine as a gegen ion gives the highest exchange capacity, while the one with trimethyl gives the lowest. To assess the solvation ability of the chloroethylated resin prepared in this work, we evolved three stages of drying consistent with the literature such that in the first stage, unmodified resin loses moisture completely (shell 1 moisture), in the second stage, chloromethylated (commercial anion exchange) resin loses moisture completely (shell 2 moisture), and in the third stage chloroethylated resin loses moisture completely (shell 3 moisture). With the increase in the duration of nitration, the shell 1 and 2 moistures first increase, but after 5 h of nitration they fall to lower asymptotic values for a large duration of nitration. However, shell 3 moisture keeps on increasing and is the highest for triphenyl phosphine gegen ion and the lowest for trimethyl amine. This increased solvation ability of chloroethylated resin is likely to be responsible for higher exchange ability of the resin reported in this work. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1735–1748, 2001

Ion-Exchange Considerations in Dilute Chemical Decontamination Processes Operated in the Regenerative Mode

Dilute chemical decontamination processes use ion-exchange resins for collecting the metal ions, radioactive contaminants, and formulation chemicals. In decontamination processes operated in the regenerative mode, the ion-exchange resin is also used for regenerating the spent formulation. Normally, the cation exchange resin is used during the regeneration stage of the process. During decontamination, the chemical formulation dissolves the contaminated metal oxide film from the system surfaces. The complexants present in the formulation form complexes with the metal ions thus released and keep them in solution. An investigation has been carried out to study the ion-exchange reaction among the complexants, the metal complexes of interest to decontamination, and the cation exchange resin. Sorption behavior of ethylenediaminetetraacetic acid on the cation exchange resin in a heavy water medium as a function of pH was studied, and the observed sorption values were compared with normal water sorption and explanations offered to account for the difference. Simultaneous pickup of different metal ions on the cation exchange resin may result in elution of one or more metal ions by another ion. Results of elution experiments are discussed. An attempt to correlate the stability of the various metal complex species formed in solution and the apparent capacity of the cation exchange resin to the metal ion is made. The effect of pH, temperature, concentrations of metal ion, and the complexants in controlling the metal ion pickup on the cation exchange resin is explained. The use of strong- and weak-base anion exchange resins in decontamination is explained.

Xylitol production from hybrid poplar wood chips pretreated by the ammonia steeping process.

Xylitol production from hemicellulosic feedstocks by a Candida sp. was inhibited by various compounds present in untreated hydrolysates. Using a pretreatment of wood chips by the ammonia steeping process, 33.6 g xylitol/L was produced from 50 g xylose/L after 5 h giving a productivity of 5.38 g/Lh and yield of 0.74 g/g. Comparable xylitol productivities were obtained upon treatment of hydrolysate with Amberlite weak base anion exchange resin.

Potentiometric titration in studies of ion exchangers

The methods for the determinations of dissociation or protonation constant and ion exchange equilibrium constant for weakly dissociating ion exchange resin and hydrous oxide by means of potentiometric titration are presented in this paper. The weakly acidic cation exchange resin and basic anion exchange resin, the chelating exchange resin in which the iminodiacetic acid groups are covalently bound to the matrix, and the chromatographic grade finely divided alumina are concerned.

Toxicity reduction of Ontario hydro radioactive liquid waste

The radioactive liquid waste (RLW) system in Ontario Hydro’s pressurised heavy water reactors collects drainage from a variety of sources ranging from floor drains to laundry waste. RLW effluent was intermittently toxic to rainbow trout and Daphnia magna during the first phase of Ontario’s Municipal Industrial Strategy for Abatement (MISA) Program, apparently as a result of the interaction of a variety of known and unknown organic and inorganic compounds. Accordingly, we employed a treatment-based approach to reducing its toxicity, supplemented by chemical analysis. Two series of toxicity reduction tests were conducted. The first series explored the potential for sorption of the possible toxicants, while the second series incorporated a wider variety of treatments. Of the 24 samples in the first test series, 17 were toxic (D. magna mortality ≥ 50%). Of the toxic samples, only 7 of 17 were still toxic after passage through an activated carbon column, but 5 of 6 samples tested remained toxic after passage through a metal chelating resin column. In the second series, at least one of the treatments was effective in reducing toxicity of all samples which were initially toxic (16 of 24 samples), but no one treatment was effective for all toxic samples. Three treatments (UV/H2O2 photo-oxidation with prior pH adjustment, or passage through a column of either a non-functionalized (N-F) resin or a mixture of N-F resin and a weak base (W-B) anion exchange resin), were effective in reducing the toxicity of more than 50% of the toxic samples; yet roughly 25% of these samples remained toxic after treatment O2 sparging, UV/H2O2 photo-oxidation without prior pH adjustment, and passage through a column of the W-B Resin were less effective, as more than 50% of the samples remained toxic after treatment. Filtering was not effective, as all of the treated samples (9/9) retained their toxicity. There was no obvious correspondence between toxicity and the concentrations of metals (Cu, Zn, Fe, A1 and Cd) nor were any simple relationships apparent between toxicity and Total Organic Carbon or NH3 concentrations. At stations where radioactive liquid wastes are segregated, toxicity was also segregated, suggesting that we may be able to address the problem at source through a combination of Best Management Practices and smaller scale treatment facilities.

SORPTION BEHAVIOR OF PERRHENATE ION ON REILLEX™-HP ANION EXCHANGE RESIN FROM NITRIC ACID AND SODIUM NITRATE/HYDROXIDE SOLUTIONS

ABSTRACT The distribution coefficients (K' d) are reported for perrhenate on the nitrate form of Reillex™-HP, a weak base anion exchange resin, as a function of nitric acid concentration from 0.100 to 10.0 M. Perrhenate K' d values were determined in 1.00 M NaNO3 from pH 2 to 13. The K'd values were determined in solutions containing 1.35 M NaNO3 and variable NaOH, 0.155 to 4.66 M, and in solutions containing 0.655 M NaOH and variable NaNO3,0.46 to 5.35 M. Maximum perrhenate loadings were <2.7% of theoretical capacity. The K' d is defined by the following equation: The total mmol of rhenium initially added is Retotal and [Re]sol is the analytical molarity of rhenium in Vsot mL of solution after a batch contact. At 1.0 M HNO3 the value of K'd is 73 mL/g. The behavior of the perrhenate system in acid can be described by assuming that perrhenic acid, HReO4, is formed with a derived acid dissociation constant of about 6.5 M. In 1.00M NaNO3from pH 2 to 13 the sorption behavior is initially what is expected for a weak base resin with an acid dissociation constant of 1.24 × 10−55 M. Thus, the K' d value decreases with pH values above the pKa value. However, instead of the value of K' d decreasing to zero at higher pH values, it becomes constant at 15 mL/g. In a solution containing 1.00 M NaOH and 1.00 M NaNO3, the value of K'd is 25 mL/g. The unusual behavior of the Reillex™-HP anion exchange resin suggests that the resin's unprotonated pyridine functionality is solvating a {Na+,ReO4 −} ion pair. The interaction of the perrhenate ion with Reillex™-HP is more involved than a simple ion exchange phenomenon and the presence of NaOH affects the resin-perrhenate interactions.

Intensification of Gold Sorption by Anion Exchange Resins

Gold extraction technology based on anion exchange resins with mixed basicity, commonly used in former soviet countries, includes a complicated and expensive process of resin regeneration and gold stripping by thiocarbamide solution. Satisfactory sorption properties of weak base anion exchange resin at pH 6–8 and low cost of metal stripping by sodium hydroxide solution have aroused considerable interest in these resins as perspective means of gold extraction from cyanide pulps on a large scale. However, the possibility of industrial use of weak base anion exchange resins is hindered by their extremely low sorption activity at pH 10.5 and the formation and release of HCN in the pulp at pH 6–8. The development of weak-based anion exchange resins which permits efficient gold sorption at pH 10.5 has already been described in literature. A special procedure for treating cyanide pulps has been devised in „Irgiredmet”. It allows a sigificant rise of gold distribution coefficient between anion exchange resins and liquid phase. Studies including counter-current tests of gold sorption by anion exchange resins of mixed and weak basicity from cyanide solutions and pulps treated accordingly were carried out. It was found that the gold capacity of mixed base resins has risen by 2–3 times, and the resin flowrate and reagent consumption during its regeneration and gold stripping by thiocarbamide solution have decreased proportionally. After special treatment the gold capacity of weak base resins in solutions and pulps is 3–6 times greater than in nontreated solutions and pulps, which indicated that the sorption capacity of resins is used to the full extent. Introduction of special treatment of cyanide pulp into existing technology makes possible an efficient industrial use of commercially available weak base anion exchange resins for gold recovery.

DETERMINATION OF ION EXCHANGE EQUILIBRIUM CONSTANTS FOR WEAKLY DISSOCIATING ION EXCHANGE RESINS

ABSTRACT In this paper the general progressive neutralization technique has been developled to evaluate the ion exchange equilibrium constant for weakly dissociating ion exchange resin. In substance, this technique is the potentiometric titration procedure of the weak acid resin weak base resin ) with the mixture solutions containing various ratios of base and salt, M(OH)n — MpXn( acid and salt, HpX—MpXn), where Mn+is metal cation, Xp−anion. According this technique, the rational equilibrium constants of the ion exchange reactions for the weak acid cation exchange resin D725 and for the weak base anion exchange resin D705 have been determined. This technique has proved useful in the determination of rational equilibrium constant of ion exchange reaction for weakly dissociating ion exchange resin.

DETERMINATION OF ION EXCHANGE EQUILIBRIUM CONSTANTS FOR WEAKLY DISSOCIATING ION EXCHANGE RESINS

ABSTRACT In this paper the general progressive neutralization technique has been developled to evaluate the ion exchange equilibrium constant for weakly dissociating ion exchange resin. In substance, this technique is the potentiometric titration procedure of the weak acid resin (weak base resin ) with the mixture solutions containing various ratios of base and salt, M(OH)n—MpXB(( acid and salt, HpX-MpX^), where M°+is metal cation, X^anion. According this technique, the rational equilibrium constants of the ion exchange reactions for the weak acid cation exchange resin D725 and for the weak base anion exchange resin D705 have been determined. This technique has proved useful in the determination of rational equilibrium constant of ion exchange reaction for weakly dissociating ion exchange resin.

Sorption of dibasic acids on weak base resins

Higher rates of uptake of dibasic acids by weak base anion exchange resins, in comparison to those of monobasic acid, have beeen satisfactorily explained on the basis of dual site adorption of divalent anion on the protonated resin sites. Due to dual site sorption, divalent anions are strongly bound to the resin matrix, thereby neutralizing the positive charges on the protonated pore surface. Hence, there is practically no exclusion of co-ions from the pores of the resin. The extent of reversibility of sorption is considerably less as a result of less repulsion of H + ions from the pore surface than that observed in monobasic acids.

Improvement of properties of weak-base anion-exchange resins by increasing their hydrophilic nature

Improvement of properties of weak-base anion-exchange resins by increasing their hydrophilic nature

Continuous chitosan hydrolyzate production by immobilized chitosanolytic enzyme from Enterobacter sp. G-1.

Chitosanolytic enzymes from Enterobacter sp. G-1 were immobilized on various carriers to continuously hydrolyze chitosan. Four different carriers were tested: FE-3901 (strong basic anion exchange resin, ionic binding), glutaraldehyde-treated FE-4612 (weak basic anion exchange resin, cross-linking), Chitopearl (chitosan beads), and alginate calcium. Glutaraldehyde-treated FE-4612 and Chitopearl immobilized more protein than the others. The enzyme immobilized on FE-3901 had the greatest activity. The activity of enzyme immobilized on FE-3901 decreased rapidly when exposed to a continuous flow of 1% chitosan. The enzyme immobilized with Chitopearl retained more than 50% of its original activity after 17 days, and the activity was fully restored by re-immobilization.

THE SORPTIONBEHAVIOR OF BORIC ACID ONWEAK-BASE ANIONEXCHANGE RESIN

ABSTRACT The sorption isotherns of boric acid on WA-21 weak-base anion exchange resin and the sorption band shape as veil as its migration velocity in a four-inch diameter ion-exchange column were studied. The isothems show S-shapes with gentle slope at both low concentration and high concentration regions. In the band migration study, it has been found that these S-shaped isotherns affected the velocities of the peak maximum as the band migrated along the column. The velocities could be calculated with the simple solute movement equation. These results suggest that sorption of nolecular species, rather than ion exchange of the counter ions is the main process that occurs inside the pores of a weak-base ion-exchange resin which is in contact with a very weak electrolytic solution, such as that of boric acid.

New Approach on Kinetics of Mercury Removal by Sulfide Regenerated Weak Base Anion Exchange Resin

AbstractThe kinetics of mercury removal by a conventional type weak base anion exchange resin, regenerated by sodium sulfide solution was studied. Assuming that the active centers of sulfide regenerated resin are located on the surface of macropores, a mathematical model which explains the extremely high specificity of this resin towards mercury was developed.

The crystal structure of lysidine · HAu(CN) 2—A model compound of a weak-base anion-exchange resin loaded with gold cyanide

The crystal structure of lysidine · HAu(CN) 2 was determined so that the influence of steric hindrance at the active site of weak-base imidazoline resins could be established. These resins, which have alkyl groups attached to the basic nitrogen, have lower basicities, and are also eluted more slowly, than imidazoline resins that have no substituents at the active site. The crystal structure of lysidine · HAu(CN) 2 (a model compound for one of the unsubstituted resins) consists of two interpenetrating hydrogen-bonded networks that are perpendicular to each other. The structure suggests that the presence of an alkyl substituent on the basic nitrogen of an imidazoline weak-base resin could hinder the approach of a hydrogen atom and the gold cyanide anion to the basic nitrogen in the functional group, thus lowering the basicity of the amine. However, the crystal structure does not explain the steric effects that have been postulated as causing the rate of elution of disubstituted imidazoline resins to be slower than that of monosubstituted imidazoline resins.

Uptake of Organic Acids by Weak Base Anion-exchange Resins

Uptake of Organic Acids by Weak Base Anion-exchange Resins

Kinetics of slow diffusing species in ion exchangers

Abstract The slow diffusion of plutonyl nitrate into a weak-base anion exchange resin has been investigated by sectioning and autoradiograping single ion exchange beads. There is clear evidence of a shell progressive diffusional effect in the early stages of the reaction, but more conventional diffusion is apparent after 336 hours of reaction. This could also be explained by Nernst-Planck diffusion of counterions with a large difference in mobility. The rate of uranium sorption by an aminophosphonic acid resin is controlled by diffusion within the ion exchange bead and the mechanism can be fitted to mathematical treatments of homogeneous diffusion and shell progressive or ash layer diffusion. The sorption of caesium by potassium copper(II) cyanoferrate is controlled by diffusion within the ion exchanger and the rate is virtually independent of particle size. Chemical reaction rate control at a moving boundary layer is the most satisfactory mathematical model and this is supported by a measured activation energy of 17.88 kcal/mol.

Ion Exchange Separation of Platinum and Palladium by Nucleophilic Displacement With Thiocyanate or Thiourea1,2

Abstract The separation of platinum and palladium, by adsorption onto weak base anion exchange resins, Amberlite XE 299, or ionex (derived from Amberlite XE-305) from 1M hydrochloric acid, followed by ligand substitution with sulfur nucleophiles is described. In the thiourea system, cationic thiourea complexes are produced, which cannot be readsorbed into the resin. In the thiocyanate system the formation of Pd(SCN)4 2- is favored in both solution and polymer phases. The Pd(SCN)4 2-. readsorption into the anion exchange resin is the basis for the separation of platinum from palladium.