Weak Base Ion Exchange Resins Research Articles

Batch screening of weak base ion exchange resins for optimized extraction of acetic acid under fermentation conditions

Acetic acid is a valuable chemical with high demand for applications in food, pharmaceutical, polymer and other industries. A total of 10% acetate in the world is produced through bio-based processes such as fermentation. Such processes require cost-effective separation technologies to make the bio-acetate product competitive on the markets. Ion exchange resins can efficiently extract acetate from the fermentation broths and due to their re-usability after regeneration, can be cost-effective with lower operation and maintenance costs. To facilitate better process design, kinetics of acetate adsorption by six different basic ion exchange resins: Amberlite FPA-53, Amberlite IRA-67, Dowex-66, Dowex Marathon WBA-2, Amberlite IRA-96 and Amberlite IRA-400; was studied using well-known linear and non-linear adsorption isotherm models. The study showed that Amberlite FPA-53 (213 mg/g wet resin) had the highest acetate adsorption capability followed by Amberlite IRA-67 (202 mg/g wet resin) and Dowex-66 (191 mg/g wet resin). Of the tested models, the acetate adsorption onto these resins was found to fit well with the Langmuir model. It was found that there was a significant effect of acetic acid concentration and pH on acetate adsorption using gel-type and macroporous resins, especially at high initial concentrations of acetate in the broth. The study further showed, that under fermentation conditions (pH of 5–7), the adsorption capacity of all the resins was lower than at the pKa for acetic acid.

Combination of Two Synchrotron Radiation-Based Techniques and Chemometrics to Study an Enhanced Natural Remineralization of Enamel.

The limitations to assess dental enamel remineralization have been overcome by a methodology resulting from the appropriate combination of synchrotron radiation-based techniques on both, infrared microspectroscopy and micro X-ray diffraction, with the help of specific data mining. Since amelogenin plays a key role in modulating the mineralization of tooth enamel, we propose a controlled ion release for fluorapatite structural ions (Ca2+, PO43–, and F–, also including Zn2+) by using weak acid and weak base ion-exchange resins in the presence of amelogenin to remineralize the surface of etched teeth. This combination provides the necessary ions for enamel remineralization and a guide for crystal growth due to the protein. Remineralized tooth samples were analyzed by applying the indicated methodology. The synchrotron data were treated using principal component analysis and multivariate curve resolution to analyze the mineral layer formed in the presence and absence of amelogenin. The remineralizing treatment created a fluorapatite layer free of carbonate impurities and with a similar orientation to that of the natural enamel thanks to amelogenin contribution.

Optimization and modeling of two-phase olive-oil washing wastewater integral treatment and phenolic compounds recovery by novel weak-base ion exchange resins

In light of the Circular Economy concept, recently emerged as a need for sustainable production, olive oil industry should be concerned to transform the whole process into environmentally friendly, which necessarily implies the treatment of the wastewater by-produced in olive mills. In this work, concentration and recovery of high-added value phenolic compounds from two-phase olive-oil washing wastewater (OOWW) and parallel effluent treatment by a ‘green process’ based on novel weak-base ion exchange (IE) resins was addressed. The key operating input factors of the resin process for the treatment and valorization of OOWW were studied, optimized and further modelled. A Box-Behnken design was implemented and the obtained data were analyzed by ANOVA and interpreted by RSM methodology. The process was ulteriorly modelled by a second-grade quadratic fitting equation comprising the significant operating variables. The optimization of the IE process performance (20.3 °C, pH0 6.7 and 114 g/L Mresin) ensured up to 92.5% recovery of total phenols concentration. Moreover, the purified stream presented good quality (56.6–83.7 mg L−1 total phenols), following standard recommendations by the FAO. The obtained information would be of key importance for the scale-up of the proposed IE operation. Both the treatment and revalorization of OOWW would help implement a definite sustainable production process of olive-oil.

Batch and fixed-bed assessment of sulphate removal by the weak base ion exchange resin Amberlyst A21

This paper investigated sulphate removal from aqueous solutions by Amberlyst A21, a polystyrene weak base ion exchange resin. Both the pH and initial sulphate concentration were observed to strongly affect sorption yields, which were largest in acidic environments. Working under optimum operational conditions, sulphate sorption by Amberlyst A21 was relatively fast and reached equilibrium after 45min of contact between the solid and liquid phases. Sorption kinetics could be described by either the pseudo-first order (k1=3.05×10−5s−1) or pseudo-second order model (k2=1.67×10−4s−1), and both the Freundlich and Langmuir models successfully fitted the equilibrium data. Sulphate uptake by Amberlyst A21 was a physisorption process (ΔH=−25.06kJmol−1) that occurred with entropy reduction (ΔS=−0.042kJmol−1K−1). Elution experiments showed that sulphate is easily desorbed (∼100%) from the resin by sodium hydroxide solutions at pH 10 or pH 12. Fixed-bed experiments assessed the effects of the initial sulphate concentration, bed height and flow rate on the breakthrough curves and the efficiency of the Amberlyst A21 in the treatment of a real effluent. In all studied conditions, the maximum sulphate loading resin varied between 8 and 40mg(SO42−)mL(resin)−1.

Development of a Modified Ion Exchange Resin Column for Removal of Gadolinium From the Moderator System of PHWRs

Gadolinium is used as neutron poison in Pressurized Heavy Water Reactors (PHWR) at 15 ppm concentration during emergency shut down and at 2 ppm during start up of the reactor. The pHa range of 5–5.5 is recommended based on the acidity requirement for maintaining gadolinium in the solution and to minimize corrosion of moderator system structural materials and radiolysis. Gadolinium has to be progressively removed as the reactor goes to power. It has been observed that gadolinium precipitates in the purification system consisting of ion exchange columns. Experimental investigations were carried out to understand the phenomenon of precipitation of gadolinium in the weak base ion exchange resin. Attempts were made to selectively cap the strong base groups in weak base resin with nitrate to prevent precipitation of gadolinium. Based on studies carried out on gadolinium pick-up and radiation decomposition of weak base anion exchange resins, a simple mixed resin column consisting of nitrate treated poly acrylic based macroporous weak base resin and a strong acid cation exchange resin has been recommended for the removal of gadolinium. It does not precipitate gadolinium and gives optimum chemistry parameters in the outlet.

Kinetics Characterization of Ion Release under Dynamic and Batch Conditions. I. Weak Acid and Weak Base Ion Exchange Resins

The aim of the present work is concerned with a study of the kinetics of release of both Ca2+ and F− from the corresponding loaded ion-exchange resins (weak acid and weak base character for Ca2+ for F−, respectively), using both dynamic and batch experimental conditions with an artificial saliva solution as the ion-exchange media at 293 and 310 K. The influence of resin particle size and the temperature were evaluated by the kinetics parameters for the effective rate of release (B) and diffusion coefficient (D). The rate of ion release increases with temperature and decreases with particle size. The experimental data were well fitted by models based on intraparticle diffusion-controlled processes. In dynamic studies, the linear dependence of −log 10(B) with the diameter of the resin particles can be applied for the estimation of B values when resins of low particle size are considered. In batch processes, although resins of low particle size can be studied, a linear relationship was only attained for the case of slow ion-exchange kinetic systems.

Removal and recovery of boron from geothermal wastewater by selective ion-exchange resins — II. Field tests

Column-mode removal of boron from geothermal wastewaters of the Kizildere Geothermal Power Station, Denizli, was performed using Diaion CRB 02 N-glucamine-type chelating resins. The resin was tested for 10 sorption-washing-elution-washing-regeneration-washing cycles in the geothermal field. The boron on the resin was eluted with 5% H 2SO 4 solution and the resin was regenerated with 4% NaOH solution prior to sorption of the following cycle. A certain decrease was observed in the break-through capacity of the resin after the first cycle. The decrease in resin capacity between cycles 2 and 7 was small, and it reached a plateau between cycles 7–10. A column-mode study was performed for the recovery ofboron from acidic eluates. For this, a weak base ion-exchange resin, Diaion WA 30, was used for separating boron from H 2SO 4 solutions collected in the field.

Removal and recovery of boron from geothermal wastewater by selective ion exchange resins. I. Laboratory tests

Boron removal from wastewaters of geothermal plant was studied using N-glucamine type chelating resins so-called Diaion CRB 01, Diaion CRB 02, Purolite S 108. The batch-mode sorption studies was performed to obtain the optimum amount of resins for boron removal from geothermal wastewater. The boron on the resin was quantitatively eluted with 5% H 2SO 4. A column-mode study was performed using weak base ion exchange resin Diaion WA 30 for the separation of boron from H 2SO 4 solution.

Cyanide recovery by ion exchange from gold ore waste effluents containing copper

The recovery of cyanide from waste effluents of the cyanidation process in gold extraction plants is important environmentally and economically. In this respect ion exchange is being tested as a possible economic and versatile method for gold ores containing copper minerals. The present study shows the potential of strong and weak base ion exchange resins, particularly the former, for separating copper cyanide complexes from these industrial effluents, and in particular the feasibility of elution with different eluants. Three possible reagents are proposed for use with these resins and the industrial effluents as load solutions: NaCN, NaSCN and NaNO3. The recovery of copper complexes from industrial effluents using a strong base resin, Lewatit MP-500, and NaSCN as eluant solution, is very high, with recoveries of over 90% in each step. Problems arise when several cycles of load and elution are carried out with the resin, and the performance of the resin decreases when working with unfiltered solutions after several operational cycles.

Cyanide recovery by ion exchange from gold ore waste effluents containing copper

The recovery of cyanide from waste effluents of the cyanidation process in gold extraction plants is important environmentally and economically. In this respect ion exchange is being tested as a possible economic and versatile method for gold ores containing copper minerals. The present study shows the potential of strong and weak base ion exchange resins, particularly the former, for separating copper cyanide complexes from these industrial effluents, and in particular the feasibility of elution with different eluants. Three possible reagents are proposed for use with these resins and the industrial effluents as load solutions: NaCN, NaSCN and NaNO 3. The recovery of copper complexes from industrial effluents using a strong base resin, Lewatit MP-500, and NaSCN as eluant solution, is very high, with recoveries of over 90% in each step. Problems arise when several cycles of load and elution are carried out with the resin, and the performance of the resin decreases when working with unfiltered solutions after several operational cycles.

Investigating the differences in acid separation behaviour on weak base ion exchange resins

Differences in acid separation behaviour on weak base ion exchange resins have been investigated in this work. Experimental data has been obtained on sorption equilibrium using various types of weak base resins and both inorganic and organic monobasic acids. A detailed analysis has been presented using the experimental data of present work and also that reported in the literature. Apart from acid concentration and type of acid, other factors such as resin type and basicity are also discussed. It was found that, resins with high basicity are most suitable for the acid removal applications. For resins with medium and weak basicity, large variation in the sorption capacity with concentration was observed. A new theoretical approach incorporating effect of resin basicity has been proposed and examined qualitatively and quantitatively using the sorption data. The results substantiate reversibility of sorption through lower values of protonation equilibrium constants and also indicate incomplete resin salt dissociation in some cases.

Modified Shrinking Core Model for Reversible Sorption on Ion-Exchange Resins

Abstract A modified shrinking core model is proposed to correlate dynamics of acid sorption on weak base ion-exchange resins in free base form. The model considers reversibility of the sorption process which is ignored in the conventional shrinking core model. The model is easy to apply and is shown to yield results which are in agreement with a computationally intensive rigorous model. The model is successfully verified using the experimental data on sorption of strong acids (HCl and HNO3) on weak base resins (Dowex WGR-2 and Amberlite IRA-93).

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.

Statics and kinetics of sorption of streptomycin on macroporous weak-base ion exchange resin D302 × 6

The resin D302 × 6 is a macroporous primary-amine ion exchanger. It can be used to purify streptomycin by sorption, as a consequence of the reversible chemical reaction between the aldehyde group of streptomycin and the primary amino group of the resin, leading to formation of a Schiff base. Anions on the resin can be exchanged by anions in the solution while the resin is sorbing streptomycin, so that the pH of the solution changes during the reaction. The pH of the solution strongly affects the sorption capacity of the resin. The sorption equilibrium of streptomycin is well described by a Langmuir equation. In the range 15–35°C, a change of temperature has a little effect on the sorption capacity. Sorption kinetics were studied using the shallow-bed method. A kinetic equation was derived based on the parallel-diffusion model proposed by Yoshida et al. Effective diffusion coefficients under several conditions were calculated from the experimental results. The rate of approach to sorption equilibrium was found to increase with temperature and concentration. The pH of the solution also affects the sorption rate.

Technetium Removal Processes for Soluble Defense High-Level Waste

AbstractTwo methods for removing technetium from soluble defense high-level waste are described. In the first method, technetium is precipitated as tetraphenylphosphonium pertechnetate and separated from the decontaminated solution using sintered metal crossflow filters. In the second method, pertechnetate is removed from solution using a strong base anion exchange resin and then eluted from the resin with nitric acid. The nitric acid is recovered by sorption of the pertechnetate on a weak base ion exchange resin. The pertechnetate is eluted from the weak base resin with NaOH and recovered by precipitation as the sulfide or oxide.

Ion exchange processes accompanied by ionic reactions

Results of kinetic studies of three different ion-exchange processes accompanied by ionic reactions, namely neutralization of strong-acid and weak-base resins, and sorption of heavy metal ions such as copper, lead and cadmium on Chelex 100 ion exchange resin are presented. Helfferich's prediction that the derived rate laws for such ion exchange processes differ appreciably from those for ordinary ion exchange in the absence of ionic reactions, is confirmed. Levenspiel's shrinking core model for fluid—solid chemical reactions, has been modified and adapted to describe the ion exchange rate processes accompanied by ionic reactions. In the sorption of heavy metal ions by Chelex 100 resins and in the neutralization process of weak-base ion exchange resins, pore diffusion inside the exchanged outer shell controlled the exchange rate process even in very dilute solutions.

Regeneration of weak base ion exchange resins

The present paper reports investigations of the regeneration of weak base ion exchange resins. A mathematical model of reaction-coupled diffusion has been applied to the regeneration kinetics. Photographic evidence is given to the sharp loading profiles resulting from that theory. By comparison of experimental data with theoretical results interdiffusion coefficients in the resin phase have been determined and their different dependency on system parameters is shown.

Application of weak base ion-exchange resins for removal of proteins

Application of weak base ion-exchange resins for removal of proteins

Application of Amberlite Xe-270 Resin to Purification of Neptunium

Amberlite XE-270, a macroreticular weak-base ion-exchange resin made by the Rohm and Haas Company, was used successfully over an 8-mo period in the Hanford Purex plant to purify ∼8 kg of 237Np. For routine purification of 237Np, the Amberlite XE-270 resin provides four important advantages over conventional microreticular strong-base resins used heretofore: 1. greatly improved thorium decontamination performance2. a much sharper neptunium elution band3. operation at 25°C rather than at 40 or 50°C4. five-fold lower resin cost.

The absorption of carbon dioxide by weak base ion exchange resins

AbstractA study of the feasibility of using ion exchange resin systems for carbon dioxide absorption from gas streams was completed with the conclusion that such a system could compete very successfully with atmospheric control systems now in use. A detailed study of such a system based on polyethylenimine showed that this material is superior to any of the commercially available weak base resins tested. The kinetic data obtained correlated very well when a model was postulated that was based on diffusive transfer through a gas film, a water film, and the resin particle in series, with diffusion with the resin particle as the rate determining step.