Weak Base Anion Exchange Research Articles

Simultaneous Removal of Heavy-Metal Ions by MnO<sub>2</sub> Loaded D301 Resin

MnO2-loaded D301 weak basic anion exchange resin was used as adsorbent to simultaneously remove Co2+, Ni2+, Cd2+, Zn2+ andCu2+ from aqueous solution contained high concentration of alkali and alkaline-earth metals ions. The effects of solution pH and coexistent ions on the adsorption were investigated. The results indicated that Co2+, Ni2+, Cd2+, Zn2+ andCu2+ can be simultaneously removed in the wide pH range of 3 to 8. The coexistence of PO43− decreased the heavy metal ions removal rate, but for other high concentrations coexistence cations and anions such as Na+, K+, Cl−, NO3−, SO42− and HCO3−, there is no significant impact on removal rate of heavy metals. The adsorption isotherm can be well described by Langmuir isotherm. The adsorption processes followed the pseudo first-order kinetics model. High adsorption capacity makes it a good promising candidate material for simultaneous removal of Co2+, Ni2+, Cd2+, Zn2+ andCu2+ from aqueous solution with the co-existence of high concentration of alkali and alkaline-earth metals ions.

Sorption studies of chromium(VI) onto new ion exchanger with tertiary amine, quaternary ammonium and ketone groups

A new acrylic anion exchanger with both tertiary and quaternary ammonium as well as ketone groups in the structural unit has been prepared by the nucleophilic substitution reaction of aminolyzed vinylacetate:acrylonitrile:divinylbenzene copolymer of porosity structure in the swelling state with 2-chloroacetone as a halogenated compound. The new compound exhibits better qualities of strong base exchange capacity than the weak base anion exchangers. The obtained acrylic anion exchanger was used to remove Cr(VI) from the aqueous solution. Batch adsorption studies have been carried out to determine the effect of contact time, concentration of hexavalent chromium in the solution and pH on the sorption capacity. The kinetic parameters were determined on the basis of the static results. The thermodynamic parameters of Cr(VI) sorption process on the anion exchanger were calculated based on the Langmuir and Freundlich isotherms. Sorption was studied in the pH range of 1.5–7 and it was found that it depends on the solution acidity. At the pH values of 3.5 and 7 the anion exchanger exhibited large values of chromium sorption capacity. The speciation of chromium was investigated in the studied pH range by the Diffuse Reflectance Spectroscopy (DRS) method. Reduction of chromium(VI) to chromium(III) under acidic conditions was observed. The performed acrylic strong base anion exchanger is superior compared to the conventional one based on the styrene:divinylbenzene matrix due to its ability for reposition of the long spacer arm for providing exchange sites, hydrophilic character of matrix, and possible hydrogen bonds provided by carbonyl functional groups.

Sorption of Sunset Yellow dye by weak base anion exchanger – kinetic and equilibrium studies

The sorption equilibrium and kinetics of Sunset Yellow dye in aqueous solutions on the weak base anion exchange resin Amberlite FPA51 were examined in this paper. The influences of phase contact time, solution pH, initial dye concentration and temperature were studied by the batch method. The amounts of dye sorbed at equilibrium changed from 9.9 to 48.7 mg/g with increasing initial dye concentration in the range 100–500 mg/L. The experimental data were analysed by the Langmuir, Freundlich, Temkin and Dubinin–Radushkevich models of adsorption. The maximum monolayer capacity was 130.6 mg/g. The sorption free energy was equal to 14.6 kJ/mol and revealed the nature of the ion exchange mechanism in this system. The kinetic data were modelled using the pseudo‐first‐order, pseudo‐second‐order (types 1–5) and intraparticle diffusion equations. The experimental data were well described by types 1–3 of the pseudo‐second‐order kinetic model.

Preparation and characterization of weak-base anion exchange membrane

Anion-exchange membranes were prepared from chlorinated polypropylene (CPP) and amine groups such as polyethyleneimine (PEI) and ethylenediamine (EDA). Its physical properties and electrochemical properties were studied. The amination rates were 50.16, 53.76, 57.11, and 65.29% for the CPP-PEI membrane and were 46.05, 47.07, 50.56, and 56.58% for the CPP-EDA membrane, respectively, at controlled temperatures. The IECs of the CPP-PEI membranes and the CPP-EDA membranes showed in the range of 1.257 ∼ 1.998 and 0.557 ∼ 1.498 mequiv./g of dry membrane, respectively. The CPP-PEI membranes possessed FICs in the range 4.941 ∼ 6.261 mequiv./g of H 2O, and those of the CPP-EDA membranes were in the range 4.198 ∼ 5.114 mequiv./g of H 2O.

New technological root for regenerating demineralized water plants for safe environment

The experiments in this work were subjected to lab-scale ion exchangers unit, consists of two kinds of ion exchangers (strong acid cation exchanger and weak base anion exchangers). The experimental investigation was directed at studying a new method for regenerating the strongly acidic cation exchanger in the demineralized water unit using one concentration of sulfuric acid (5%) directly without any precipitation problems. Experiments show that using sulfuric acid in the regeneration is equally efficient as that of hydrochloric acid solution in the production of dematerialized water (110 bed volume). The first objective of this study was to use sulfuric acid solution instead of hydrochloric acid solution because it is cheaper and non corrosive. The other benefits could be gained from the effluent (sodium hydroxide solution) which comes out of the anion exchanger columns instead of disposing them. Key words: Cation exchanger, anion exchanger, backwash, regeneration, rinsing.

A weak-base fibrous anion exchanger effective for rapid phosphate removal from water

This work investigated that weak-base anion exchange fibers named FVA-c and FVA-f were selectively and rapidly taken up phosphate from water. The chemical structure of both FVA-c and FVA-f was the same; i.e., poly(vinylamine) chains grafted onto polyethylene coated polypropylene fibers. Batch study using FVA-c clarified that this preferred phosphate to chloride, nitrate and sulfate in neutral pH region and an equilibrium capacity of FVA-c for phosphate was from 2.45 to 6.87 mmol/g. Column study using FVA-f made it clear that breakthrough capacities of FVA-f were not strongly affected by flow rates from 150 to 2000 h −1 as well as phosphate feed concentration from 0.072 to 1.6 mM. Under these conditions, breakthrough capacities were from 0.84 to 1.43 mmol/g indicating high kinetic performances. Trace concentration of phosphate was also removed from feeds containing 0.021 and 0.035 mM of phosphate at high feed flow rate of 2500 h −1, breakthrough capacities were 0.676 and 0.741 mmol/g, respectively. The column study also clarified that chloride and sulfate did not strongly interfere with phosphate uptake even in their presence of equimolar and fivefold molar levels. Adsorbed phosphate on FVA-f was quantitatively eluted with 1 M HCl acid and regenerated into hydrochloride form simultaneously for next phosphate adsorption operation. Therefore, FVA-f is able to use long time even under rigorous chemical treatment of multiple regeneration/reuse cycles without any noticeable deterioration.

Removal of Arsenate from Aqueous Solution by Manganese and Iron (hydr)oxides Coated Resin

A composite adsorbent MIR, manganese and iron (hydr)oxides coated resin, was prepared by coating manganese and iron (hydr)oxides onto the weak basic anion exchange resin D301. The effects of solution pH, contact time, ionic strength, and coexisting ions on arsenate removal with MIR were investigated in batch experiments. The results showed that As(V) can be effectively removed in a wide pH range of 4 ∼ 9. The presence of coexisting anions such as had no noticeable effect on arsenate removal efficiency. However, were found to interfere with the arsenate removal significantly. Arsenate adsorption efficiency decreased with the increment of ion strength of the solution. The adsorption isotherm could be well described by the Freundlich model. A pseudo second-order kinetics was able to provide a realistic description of the adsorption kinetics.

Poly(4-vinylpyridine) resins towards perrhenate sorption and desorption

The series of the 4-vinylpyridine and divinylbenzene cationic polymers (4-VP/DVB) in the presence of toluene or toluene and heptane (100 wt.% in respect to the monomers mixture) were synthesised in order to obtain weak base anion exchangers with gel or macroporous structure. The strong base anion exchangers were obtained by its quaternization with alkyl iodide: propyl iodide, butyl iodide and pentyl iodide. The FTIR spectra of anion exchangers were useful to characterize resins and degree of quaternization. The sorption and desorption ability of rhenium, Re(VII), as perrhenate anion from acid solution (sulphuric or hydrochloric acid 0.1 M) were tested in batch and dynamic methods. The sorption of Re(VII) from the solution of 50 mg Re/L reached about 60 mg/g of dry resin in batch method. All the investigated anion exchangers characterize with high selectivity of perrhenate from multicomponent solution containing chlorocomplexes of PGM metals (Pt, Pd) and Au. The sorption ability of PGM metals and Re(VII) is on the same level as from the solution containing only one ion. The dynamic method of sorption allowed to reach the sorption of Re(VII) up 200 mg/g of resin. The desorption of Re(VII) by ammonium (5 wt.%), with the yield about 97%, was possible only from the weak base anion exchangers, where the degree of sorption and desorption is on the same level in the second and other cycles. The sorption ability of Re(VII) on new anion exchanger is comparable to commercial anion exchangers, like Reillex HP.

Application of Weak Base Anion Exchanger in Sorption of Tartrazine from Aqueous Medium

Decolorization of wastewaters containing dyes is a worldwide problem for which diverse technologies have been applied. In this study, the removal of tartrazine dye from aqueous solutions by the weak base anion exchanger Amberlite FPA51 was investigated as a function of phase contact time, anion exchanger particle size, solution pH, initial dye concentration, and temperature. The amounts of tartrazine adsorbed at equilibrium were found to be 9.9, 19.9, 29.9, and 49.7 mg/g for the dye solutions of the initial concentrations 100, 200, 300, and 500 mg/L, respectively. The maximum monolayer capacity Q0 calculated from the Langmuir equation was 140.8 mg/g. The kinetic data obtained at different concentrations were modelled using the pseudo-first order and the pseudo-second order equations. The intraparticle diffusion model as well as the Boyd equation were applied to identify the rate controlling step of the adsorption.

Removal of Co2+ and Sr2+ from a Primary Coolant by Continuous Electrodeionization Packed with Weak Base Anion Exchange Resin

The rapid development of the nuclear power plant (NPP) in China leads to increasing attention to the minimization of radioactive waste. The primary coolant is one of the sources of low-level radioactive wastewater and must be decontaminated before its discharge to the environment. One of the possibilities is by means of continuous electrodeionization (CEDI) technology. In this paper the lab-scale experiments demonstrate that CEDI can offer favorable decontamination of primary coolant in NPP, with minimized radioactive spent resin production. Displacement of the anion exchanger by weak base anion exchangers in a CEDI module can improve the Co2+ and Sr2+ removal. In the dilute effluent of the modified module, Co2+ and Sr2+ concentrations are below 2 ng·l–1 and 58 to 114 ng·l–1, respectively, which is much lower than the commercial one of 205 to 289 ng·l–1 and 268 to 326 ng·l–1. This displacement has a negligible influence on the electrical resistance of the module.

Weak Base Anion Exchanger Amberlite FPA51 as Effective Adsorbent for Acid Blue 74 Removal from Aqueous Medium – Kinetic and Equilibrium Studies

In this work, the macroporous anion exchange resin – Amberlite FPA51, is proposed as the effective adsorbent for the removal of Acid Blue 74 from aqueous solutions. The sorption mechanism was investigated under static conditions taking into account the phase contact time, solution pH, initial dye concentration, and temperature. The equilibrium data were fitted to the Langmuir, Freundlich, and Dubinin-Radushkevich isotherm models. The maximum monolayer capacity Q 0 was 123.8 mg/g. The adsorption kinetics was found to follow the pseudo-second order model. The sorption energy was equal to 14.5 kJ/mol and indicated that the adsorption process of the dye may be described via a chemical anion-exchange mechanism.

Dynamics of the chloride sorption by weak basic polyacrylic anion exchanger amberlite IRA 67

The non-equilibrium dynamics of hydrochloric acid sorption by the weak basic polyacrylic anion exchanger Amberlite IRA 67 has been investigated during the sorbent regeneration under the fluidization condition. The value of the kinetic coefficient of internal mass transfer was determined at different flow rates of the model solution at the stage of water desalting. The sorbent regeneration under the fluidization condition was found to tangibly affect the dynamics of water desalting process due to the classification of anionexchanger grains in terms of their size at the stage of regeneration. The study of the process of sorption dynamics of chloride ions by the weak basic anion-exchanger Amberlite IRA 67 makes it possible to avoid the frequent problem of biological fouling of OH-filters at the stage of water desalting.

Separation of Boron from Geothermal Water Using a Boron Selective Macroporous Weak Base Anion Exchange Resin

In this study, batch and column mode tests were performed to evaluate the efficiency of boron removal from geothermal water containing 10-11 mg B/L using Lewatit MK 51 which is a macroporous weak base anion exchange resin with polyhydroxyl groups showing a very high selectivity and capacity for boron. The optimum resin amount for boron removal from geothermal water was determined as 4.0 g resin/L-geothermal water. It was found that the sorption kinetics was influenced by particle size of the resin and temperature. The stirring rate had almost no effect on kinetic performance of the resin. According to the results of column-mode study performed, breakthrough and total capacities of the resin were obtained as 2.75 and 4.98 mg/mL-resin, respectively.

Sorption of methanal by a weak basic anion exchanger

Peculiarities of the sorption of methanal on a polyfunctional anion exchanger are investigated. Based on the sorption isotherm, it is established that the distribution coefficient of the aldehyde in the ion exchanger-solution system depends exponentially on the concentration of the external solution. From breakthrough curves of sorption, the rate-determining stage of the absorption of the aldehyde in dynamic conditions is estimated. Structural changes in the sorbent phase saturated with methanal are supported by IR spectroscopy.

Simultaneous adsorption of lead and cadmium on MnO 2-loaded resin

MnO 2-loaded D301 weak basic anion exchange resin has been used as adsorbent to simultaneously remove lead and cadmium ions from aqueous solution. The effects of adsorbent dosage, solution pH and the coexistent ions on the adsorption were investigated. Experimental results showed that with the adsorbent dosage more than 0.6 g/L, both Pb 2+ and Cd 2+ were simultaneously removed at pH range 5–6. Except for HPO 4 2−, the high concentration coexistent ions such as Na +, K +, Cl −, NO 3 −, SO 4 2− and HCO 3 −, showed no significant effect on the removal efficiency of both Pb 2+ and Cd 2+ under the experimental conditions. The coexistence of Mg 2+, Ca 2+ caused the reduction of Cd 2+ removal, but not for Pb 2+. The adsorption equilibrium for Pb 2+ and Cd 2+ could be excellently described by the Langmuir isotherm model with R 2 > 0.99. The maximum adsorption capacity was calculated as 80.64 mg/g for Pb 2+ and 21.45 mg/g for Cd 2+. The adsorption processes followed the pseudo first-order kinetics model. MnO 2-loaded D301 resin has been shown to have a potential to be used as an effective adsorbent for simultaneous removal of lead and cadmium ions from aqueous solution.

Study of nitric acid leachout characteristics from weak base anion exchanger to maintain a specified pH regime during Gd(NO3)3 removal from moderator system of 540 MWe PHWRs

AbstractNitric acid leachout characteristics from weak base anion exchanger (WBA) have been experimentally evaluated as a function of total nitric acid loading at a given flow velocity. An empirical first order model is used to explain the column outlet behaviour. Based on the experimental evaluation, a column configuration of a strong acid cation exchanger (SAC) topped mixed bed of SAC and WBA followed by a 5% nitric acid loaded WBA as the bottom layer of the column has been used to remove Gd(NO3)3 from water while maintaining the column outlet pH in the range of 5.0–5.5.

Adsorption of anionic textile dye Acid Green 9 from aqueous solution onto weak or strong base anion exchangers

AbstractThe aim of this work is to study the thermodynamic and kinetic studies with regard to the adsorption of Acid Green 9 (AG9) on the most efficient resin, namely, acrylic weak base anion exchange resin with ethylenediamine‐functional groups (A1) selected from several anion exchange resins. The influence of the various experimental parameters such as, pH, initial dye concentration, contact time, temperature, and adsorbent dose was investigated by batch experiments. The extent of the dye adsorption increased with the decrease of the initial dye concentration and the increase of the contact time, temperature, and amount of the adsorbent. Adsorption process was quantitative and very fast at low concentrations of the dye. To investigate the mechanism of the adsorption and potential rate‐controlling steps, pseudo first‐ and second‐order, as well as intraparticle diffusion kinetic equations have been used. The adsorption kinetic of AG9 dye from aqueous solution onto A1 could be described by the pseudo second‐order reaction model. The obtained results are in agreement with the Langmuir and Freundlich models. In the optimum conditions established, an adsorption capacity of 500 mg textile dye (72% purity) g−1 adsorbent (at 293 K) was reached. Desorption experiments by batch and dynamic methods were performed using a solution of 0.05 mol L−1 NaOH. A series of 13 adsorption–desorption cycles were carried out by the dynamic method with a quantitative adsorption and the desorption efficiency higher than 95%. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Ion Exchange Functional Nanofibers

AbstractWe have synthesized a series of ion exchange functionalized fibers (IXF) from polystyrene (PS) and polyacrylonitrile (PAN). To obtain strong-acid cation exchange fibers, polystyrene was sulfonated using specific sulfonation protocols. Micron sized fibers (average diameter of 100m) were then produced from the functionalized polystyrene using a single-screw extruder equipped with a 30 hole spinneret with orifice diameter of 0.5 mm with a precise screw speed of 5 rpm, pump speed of 15 rpm, and with a feed rate of 2.4 cc/min. The extruder zone temperature was kept at 250 – 270 °C. Fiber was drawn at 120 degree with a draw ratio of 2. Electrospinning of functionalized polystyrene was also carried out to produce ultrafine functionalized fibers of 100 nm in average diameter. We have also electrospun polystyrene and polyisoprene blended nanofibers to increase the strength of the resulting blend nanofibers compared to pure PS nanofibers. To synthesize weak-acid cation exchange fibers polyacrylonitrile (PAN) was electrospun and the nanofibers obtained were alkaline hydrolyzed with 2 N NaOH for 20 minutes at room temperature to convert nitrile bonds to carboxylate. Cation exchange capacity (CEC) of the microfibers and nanofibers was determined. Sulfonated PS microfibers show high CEC of 4.0 meq/gm compared to that of nanofibers with 2.5 meq/gm. CEC of blended nanofibers of PS and polyisoprene was 2.0 meq/gm. In case of PAN fibers, nanosized electrospun fibers were found to show a CEC of 1.5 meq/gm. Weak-base anion exchange fiber synthesis was undertaken using appropriate protocol and its CEC was measured. For all IXF synthesized, fiber diameter was measured using SEM, degree of functionalization was qualitatively determined using FTIR and ion exchange capacity was computed after mass balance on a binary exchange system after equilibrium.

Separation of protein charge variants with induced pH gradients using anion exchange chromatographic columns

This work concerns the chromatographic separation of protein charge variants using pH gradients generated by step changes in buffer composition with weak base anion exchange columns. A local equilibrium model is first developed to describe pH transitions occurring in the column using buffers comprising neutral, zwitterionic or positively charged species. Model predictions, based solely on the resins' titration curves and obtained with the method of characteristics, show, in excellent agreement with experiments, that induced pH gradients of varying durations and shapes can be obtained with a broad range of buffer systems including Tris, Bis-Tris propane, histidine, and their mixtures and ethanolamine. The separation of protein charge variants is then demonstrated for bovine apo-transferrin and for a monoclonal antibody. The resolution of the charge variants present in these proteins, demonstrated via isoelectric focusing analyses, is obtained for conditions amenable to scale-up for preparative purposes; that is larger particle sizes (90 mum), higher flow rates (100-600 cm/h), and higher protein loads (2-5 mg/mL). Because the approach requires only step changes in buffer composition and commonly available, unretained buffers species, practical implementation is straightforward. The focusing effect of the induced pH gradient results in relatively sharp peaks and substantial resolution even for these conditions.

Treatment of drilling wastewater using a weakly basic resin

Macroporous weak basic anion exchanger (D301R) was used to remove organic substances from drilling wastewater. The effect of pH, temperature and contact time on adsorption behavior was investigated in batch experiments, which indicated that the COD (Chemical Oxygen Demand) removal ratio of drilling wastewater was approximately 90%, and the COD of treated wastewater was below 70 mg/L under appropriate operating conditions. A mixed liquor of NaOH and NaCl was selected as desorbent because of its better elution performance. The results of column dynamic adsorption and regeneration showed that the COD of wastewater could be efficiently removed by D301R resin, and the resin was easily regenerated by the selected desorbent.