Weak Base Anion Exchange Research Articles

Ion pairing based polyurethane foam sorbent packed column combined with inductively coupled plasma–optical emission spectrometry for sensitive determination and chemical speciation of bismuth(III & V) in water

The sorption profile of trace concentrations of bismuth(III) species from aqueous KI–H2SO4 media onto the ion pairing procaine hydrochloride (PQ+.Cl−) based polyurethane foam (PUFs) was studied. A dual–mode of bismuth(III) sorption as a ternary complex ion associate [PQ+.BiI4−] involving absorption due to a “weak base anion exchanger” and an added component for “surface adsorption” seems the proposed mechanism for bismuth(III) retention. The capacity of bismuth(III) sorption was found equal 40.05±1.10mgg−1. Complete separation of spiked bismuth(III) at various concentrations (5–15μgmL−1) from water onto the proposed sorbent packed columns at 5mLmin−1 flow rate was successfully achieved. The retained bismuth(III) species were recovered quantitatively from the sorbent packed columns (98.4±2.4%, n=5) with HNO3 (1.0molL−1). Bismuth(V) after reduction to Bi(III) was also preconcentrated, recovered from the sorbent packed column and subsequently analyzed by inductively coupled plasma–optical emission spectrometry (ICP–OES). The height equivalent to the theoretical plates (HETP), number of plates (N), critical and breakthrough capacities of sorbent packed column towards bismuth(III) retention were evaluated. Based on these results, a simple and sensitive PQ+.Cl−–PUF packed column was developed for determination and speciation of trace concentrations of bismuth(III & V) species in water by ICP–OES. The limits of detection (LOD) and quantification (LOQ) of Bi(III) were found 0.09 and 0.30μgL−1, respectively. The relative standard deviation (RSD) for 5 replicates of 50ngL−1 Bi at 2.0mLmin−1 flow was ±3.7%. The proposed column was validated and applied for the preconcentration, separation and subsequent determination of analyte in Environmental water reference material (TMDW) and water samples. The results were found to be in good agreement with the CRM at the 95% confidence level.

Phosphate removal from aqueous solution using a hybrid impregnated polymeric sorbent containing hydrated ferric oxide (HFO)

AbstractBACKGROUNDThis study evaluated a polymeric ion exchanger impregnated with nanoparticles of hydrated ferric oxide as a selective sorbent for anionic P(V) species. The hybrid impregnated anion exchanger (HAIX) employed as sorbent combines the durability and mechanical strength of a polymeric weak base anion exchange resin with the high sorption affinity of hydrated ferric oxide towards P(V) species.RESULTSThe P(V) loading capacity of the sorbent at a pH simulating the expected conditions in treated wastewaters was 92 ± 3 mg P‐PO4 g−1 in single component solutions. The sorption of P(V) is affected slightly by the common ions typically present in these effluents such as Cl−, SO42− and NO3−, and a reduction of only 5% was observed (89 ± 2 mg P‐PO4 g−1) in multicomponent solutions. The sorbent can be regenerated (95 ± 3%) using 4% (w/w) sodium hydroxide solution.CONCLUSIONSHAIX displays high selectivity for phosphate and small affinity for SO42−, NO3− and Cl− ions, which provides excellent conditions for its application at pH values typical of secondary wastewater effluents. HAIX exhibits higher and competitive phosphate removal capacity compared with data reported in the literature for materials based on HFO and for adsorbents prepared by impregnation of HFO onto polymeric supports. © 2015 Society of Chemical Industry

Impacts of integrated strong-acid cation exchange and weak-base anion exchange process for successful removal of saline toxicity from model olive mill wastewater

In the present work, the performance of a fixed-bed ion exchange (IE) process comprising novel strong-acid cation exchange and weak-base anion exchange resins was examined for the removal of the ionic species, that is, sodium and chloride ions, responsible for the high salinity of olive mill wastewater from an olive mill working with the two-phase decanting technology exiting a primary–secondary treatment (OMW-2ST). Sodium IE efficiency was found to increase with an increment in the pH value up 5, whereas the optimum pH for chloride IE was equal to 1. Equilibrium behaviour of both species was accurately predicted by Langmuir isotherm, showing sodium uptake is 53.9% higher than for chloride. Sodium and chloride removal efficiencies decreased (from 97.0 to 74.0% and from 95.0 to 77.0%, respectively) when their initial concentration increased from 250 to 1000mgL−1. Finally, the integrated IE system in continuous mode ensured 80–90% average removal efficiencies for both ionic species and conductivity. IE efficiency loss below 5% after several regeneration cycles is a technical-economical key fact. The final treated effluent complied with the standards established by the Food and Agricultural Association (FAO) with the goal of reusing the regenerated water for irrigation purposes.

The Effect of Accompanying Anions on Arsenate Sorption onto Selective Sorbents

Arsenate sorption onto inorganic and composite inorganic/organic selective sorbents based on ferric oxide/oxohydroxide was tested under varying concentration of accompanying anions (chlorides, sulfates, phosphates, and silicates). Among the studied anions, phosphates showed the strongest influence on arsenic removal. Ferric oxide based sorbents were also compared to weak and strong base anion exchangers and other metal oxide (ceric oxide, zirconium oxide) based composites under the presence of accompanying anions (chlorides and sulfates). Their performance was comparable to ferric oxide composites. Ferric oxide/oxohydroxide based composites are able to take up arsenates (with capacity of tens of mmol·L−1) even at the presence of 100 mg·L−1 of chlorides and sulfates where the breakthrough capacities of weak and strong base anion exchangers dropped to less than 2% (units of mmol·L−1) of the values obtained in the absence of accompanying anions (hundreds of mmol·L−1).

Adsorption behavior of α-tocopheryl succinate and α-tocopheryl polyethylene glycol succinate onto weakly basic anion exchange resins

Polyethylene glycol (PEG) esters are important, nontoxic and biodegradable non-ionic surfactants. A key procedure in producing PEG esters is their separation from unreacted or excess acids. We propose an adsorption method using the weakly basic anion exchange resins for the separation of organic acids and PEG esters for the first time. With α-tocopheryl polyethylene glycol succinate (TPGS) and α-tocopheryl succinate (α-TS) as the examples of PEG ester and organic acid, respectively, single-component equilibrium experiments revealed the great potential of this method. Studies on the adsorption equilibrium, thermodynamics and kinetics of α-TS onto a weakly basic anion exchange resin were also carried out. This research is not only important for the production of TPGS, but also instructive for the separation of other PEG-esters from the reaction mixtures.

Selection of Ion Exchange Resins for Tungsten and Molybdenum Separation

A solution containing tungsten and molybdenum was acidified using hydrochloric acid, and the ability of several commercial ion exchange resins to separate tungsten and molybdenum was evaluated. The results from the acidification test indicate that when the pH of the solution is adjusted to 7.0, WO42- is polymerized into HW6O215-, while MoO42- is not. The test results of resins selection show that the D213 resin and the D308 resin are superior to other resins in separating low concentrations of tungsten and molybdenum, whereas the D201 resin and the D309 resin are suitable for separating high concentrations of tungsten and molybdenum. The results from the column test indicate that weak-base anion exchange resins are better than strong-base anion exchange resins for both low and high concentrations of tungsten and molybdenum.

The influence of ion‐exchange substrates on grass growth in sandy soils

AbstractThe effect of 2% (v/v) addition of ion exchange substrate to a sandy soil on the growth of Dactylis glomerata L., used as a test species, was studied. Four different exchange additives having pH values in the range 4.45–7.14 were evaluated in pot experiments. These additives were prepared as mixtures of monoionic forms of a strong acid cation exchanger and a weak base anion exchanger, loaded with nutrient ions. The additions of the ion exchange substrates to the sand affected plant growth advantageously, increasing the total dry biomass 3.8– 8.5 times. The most efficient additive appeared to be the substrate with the lowest pH because it contained the largest stock of nutrient elements. The excessive acidity of the additive was spontaneously neutralized in the mixtures with sand due to reaction of the acid excess with carbonates present in the natural sandy soil.

ICP-OES Determination of Titanium (IV) in Marine and Wastewater Samples after Preconcentration onto Unloaded and Reagent Immobilized Polyurethane Foams Packed Columns

A novel method that utilizes untreated and polyurethane foam (PUF) physically immobilized with the reagent 4-(2-pyridylazo) resorcinol (PAR) or 2, 3, 5-triphenyl-2H-tetrazolium chloride (TZ+Cl-) as solid phase extractor packed column has been developed for preconcentration and subsequent determination of titanium(IV) ions in marine and wastewater samples. The method is based on retention of the titanium(IV) traces present in aqueous media at pH 3-4 onto the reagent treated PUF packed column, followed by recovery with HNO3 (2.0 mol dm-3) and subsequent ICP-OES determination. The uptake of titanium species onto the unloaded- and reagent impregnated PUF was fast and followed a first-order rate equation. Titanium sorption onto PUF followed Langmuir, Freundlich and Dubinin- Radushkevich (D-R) type isotherm models. Thus, a dual-mode sorption mechanism involving absorption related to “weak-base anion exchange” and an added component for “surface adsorption” seems a more likely retention model. PAR-immobilized PUF packed column has been applied successfully for complete collection of titanium(IV) species in fresh and wastewater samples at low level of titanium (<0.5 ng Ti mL-1) at pH 3-4. The retained titanium species were then recovered (97-101%) from the packed column with HNO3 and determined by ICP-OES. The proposed PUF packed column method was further applied for analysis of picomolar concentrations of dissolved Ti species in marine water.

Simultaneous Removal of Azo and Phthalocyanine Dyes from Aqueous Solutions Using Weak Base Anion Exchange Resin

The performance of the Purolite A847 weak basic anion exchanger in the simultaneous removal of the azo dye Lanasyn Navy M-DNL (LNCr) and the phthalocyanine dye Acid Blue 249 (CuPc) from acidic aqueous solutions was studied under dynamic conditions. The comparison of FTIR spectra of unloaded and dye-loaded anion exchangers made it possible to consider suitable sorption mechanisms. The results of dynamic experiments revealed that anion exchanger had a greater dynamic sorption capacity with a longer breakthrough time and a shorter length of mass transfer zone when both dyes LNCr and CuPc were removed from the one-component solution as compared to those of their mixture. Models of Wolborska and Juang were found to be suitable to predict the character of breakthrough curves and to determine the characteristic parameters of the Purolite A847 column useful for process design: the mass transfer coefficient β (1/min) and time at the break point τ (minutes). The result would be useful in the design of wastewater treatment plants for removal of azo and phthalocyanine dyes from aqueous solutions and water recycling.

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.

Adsorption of zinc and cyanide from cyanide effluents on anionic ion-exchange resin

The adsorption of zinc and cyanide from cyanide effluents onto strong and weak basic anion exchange resins was studied in a batch adsorption system. Factors influencing the adsorption rates such as resin selection, resin amounts, contact time and temperature were studied and scanning electron microscopy-energy disperse spectroscopy( SEM-EDS) was used in the analysis. The present study shows that the adsorption capacity of resin 201×7 is better than that of resin 301. The adsorption process was relatively fast and came to equilibrium after 60 min. The kinetic data were analyzed with three models and the pseudo-second-order kinetic model was found to agree with the experimental data well. The equilibrium data could also be described well by Langmuir isotherm model. Thermodynamic parameters such as enthalpy change(ΔH0), free energy change(ΔG0) and entropy change(ΔS0) were calculated and the adsorption process was spontaneous and endothermic.

Preparation of a novel anion exchange group modified hyper-crosslinked resin for the effective adsorption of both tetracycline and humic acid

A novel hyper-crosslinked resin (MENQ) modified with an anion exchange group was prepared using divinylbenzene (DVB) and methyl acrylate (MA) as comonomers via four steps: suspension polymerization, post-crosslinking, ammonolysis and alkylation reactions. The obtained resin had both a high specific surface area (793.34 m2·g−1) and a large exchange capacity (strong base anion exchange capacity, SEC: 0.74 mmol·g−1, weak base anion exchange capacity, WEC: 0.45 mmol·g−1). XAD-4 was selected as an adsorbent for comparison to investigate the adsorption behavior of tetracycline (TC) and humic acid (HA) onto the adsorbents. The results revealed that MENQ could effectively remove both TC and HA. The adsorption capacity of XAD-4 for TC was similar to that of MENQ, but XAD-4 exhibited poor performance for the adsorption of HA. The adsorption isotherms of TC and HA were well-fitted with the Freundlich model, which indicated the existence of heterogeneous adsorption through cation-π bonding and π-π interactions. The optimal solution condition for the adsorption of TC was at a pH of 5–6, whereas the adsorption of HA was enhanced with increasing pH of the solution.

Comparative Study of Indion-AGR and Duolite A-638 Anion Exchange Resins by Application of &lt;SUP&gt;131&lt;/SUP&gt;I and &lt;SUP&gt;82&lt;/SUP&gt; Br as a Tracer Isotopes

The present study deals with modeling of ion-isotopic exchange reaction kinetics by application of radioactive tracer isotopes 82Br and 131I. The bromide and iodide ion-isotopic exchange reactions was carried out by using weak base anion exchange resins Indion-AGR and Duolite A-638. It was observed that for both the resins, reaction rate decreases with rise in temperature and increases with increase in ionic concentration. The study was extended further for characterization of these resins based on their performance under different operational parameters. It was observed that the percentage/amount of ions exchanged and distribution coefficient values calculated for Duolite A-638 was higher than Indion-AGR resins under identical operational parameters, indicating superior performance of Duolite A-638 over Indion-AGR resins.

Comparative Study of Indion-870 and Duolite A-611 Anion Exchange Resins by Application of &lt;SUP&gt;131&lt;/SUP&gt;I and &lt;SUP&gt;82&lt;/SUP&gt; Br as a Tracer Isotopes

The present study deals with modeling of ion-isotopic exchange reaction kinetics by application of radioactive tracer isotopes 82Br and 131I. The bro mide and iodide ion-isotopic exchange reactions was carried out by using weak base anion exchange resins Indion-A GR and Duolite A-638. It was observed that for both the resins, reaction rate decreases with rise in temperature and increases with increase in ionic concentration. The study was extended further for characterizat ion of these resins based on their performance under d ifferent operational parameters. It was observed that the percentage/amount of ions exchanged and distribution coefficient values calculated fo r Duolite A-638 was higher than Indion-A GR resins under identical operational parameters, indicat ing superior performance of Duolite A-638 over Indion-AG R resins. Radio isotopes find applications in several fields of which ind ustrial app licati ons consti tut e a majo r po rt io n with respect to the quantum of activ ity used and the economic benefits accrued. Industrial applicat ions of radioisotopes can be main ly categorized into two. The first one being the use of rad iati on fro m sealed sources of rad ioi sotopes or fro m elec tron beam accelerator s for in dustrial pr o cessing, n on- destructive testing. The second major group of applications is the use of radiotracers in inventory control, study of process parameters, trouble shooting in industrial systems, flo w measurements , leakage stud ies etc. The economic benefits that may be derived fro m the use of the radioisotope technology are great, a fact that is recognized by the governm ents of developing countries. Though radioisotopes have been applied to the solution of problems in industry for over 50 years, research and development of the techno logy cont inues unabated . There are t wo main reasons for the continu ing interest. Firstly, it is industry driven . Because o f th eir un ique p ropert ies , radi oact ive isotopes can be used to obtain information about plants and processes that cannot be obtained in any other way. Often, the info rmat ion is obtained with the p lant on-stream and

Weakly-Basic Anion Exchange Resin Scavenges Impurities in Ionic Liquid Synthesized from Trialkyloxonium Salt

A new purification method of ionic liquids made from trialkyloxonium salts (Meerwein reagents) has been established. 1H and 19F NMR spectroscopy clarified the presence of 1-methylimidazolium ([Hmim]+) and trifluoro(1-methylimidazole)boron ([BF3(mim)]) as impurities occurring in the crude ionic liquid, 1-ethyl-3-methylimidazolium tetrafluoroborate ([emim]BF4). The Lewis acidic parts of these impurities, that is, H+ and BF3, were demonstrated to be able to transfer to dimethylamino groups of the weakly basic anion exchange resin (DOWEX MARATHON WBA) in aqueous solutions, releasing 1-methylimidazole (mim). The adsorption isotherms of [Hmim]BF4 and [BF3(mim)] resulted in the equilibrium constants (K) of the reactions with the resin ([Hmim]BF4: log K ≈ 1.7, [BF3(mim)]: log K = −0.17 ± 0.03), indicating that the impurities show a difference in the reactivity with the resin. The volatiles (mim and water) are possible to be removed by evaporation under reduced pressure. Although intense reddish brown color was given to the residual oil of [emim]BF4, further purification and decolorization have been achieved by using silica-gel column chromatography (eluent: acetone) and treatment with activated carbon in water. Finally, the purified [emim]BF4 was successfully obtained as an almost colorless oil. The resin after use can be regenerated simply by washing with 1 M NaOH aq and deionized water.

Evaluating of arsenic(V) removal from water by weak-base anion exchange adsorbents

Arsenic contamination of groundwater has been called the largest mass poisoning calamity in human history and creates severe health problems. The effective adsorbents are imperative in response to the widespread removal of toxic arsenic exposure through drinking water. Evaluation of arsenic(V) removal from water by weak-base anion exchange adsorbents was studied in this paper, aiming at the determination of the effects of pH, competing anions, and feed flow rates to improvement on remediation. Two types of weak-base adsorbents were used to evaluate arsenic(V) removal efficiency both in batch and column approaches. Anion selectivity was determined by both adsorbents in batch method as equilibrium As(V) adsorption capacities. Column studies were performed in fixed-bed experiments using both adsorbent packed columns, and kinetic performance was dependent on the feed flow rate and competing anions. The weak-base adsorbents clarified that these are selective to arsenic(V) over competition of chloride, nitrate, and sulfate anions. The solution pH played an important role in arsenic(V) removal, and a higher pH can cause lower adsorption capacities. A low concentration level of arsenic(V) was also removed by these adsorbents even at a high flow rate of 250-350 h(-1). Adsorbed arsenic(V) was quantitatively eluted with 1 M HCl acid and regenerated into hydrochloride form simultaneously for the next adsorption operation after rinsing with water. The weak-base anion exchange adsorbents are to be an effective means to remove arsenic(V) from drinking water. The fast adsorption rate and the excellent adsorption capacity in the neutral pH range will render this removal technique attractive in practical use in chemical industry.

Kinetics of formaldehyde sorption by a weakly basic anion exchanger under dynamic conditions

The kinetic principles of sorption of formaldehyde sorption on a polyfunctional weak-basic anion exchanger are considered. It is found that the limiting step of sorbate uptake is external diffusion. Parameters of formaldehyde sorption from aqueous solutions under dynamic conditions are determined.

Adsorptive removal of arsenic(III) ions from industry wastewaters using a weak anion exchanger prepared from banana stem

AbstractThe performance of an anion exchanger prepared from banana stem (BS), a lignocellulosic residue for the removal of As(III) from aqueous solutions has been evaluated in this study. The adsorbent (BS‐DMAHP) containing dimethylaminohydroxypropyl (DMAHP) functionality was prepared by the reaction of BS with epichlorohydrin and dimethylamine followed by treatment with hydrochloric acid to convert it into the chloride form of the anion exchanger. The adsorbent characterization was done with the surface area analyzer, Fourier transform infrared spectroscopy (FTIR), and potentiometric titrations. Adsorption equilibrium study was conducted with a concentration range of 10–300 mg/L, for As(III). The Langmuir isotherm model was found to be the best fit model. The maximum adsorption capacity was found to be 65.11 mg/g. Adsorption has been found to be endothermic and follows second‐order reversible kinetics. The removal efficiency of BS‐DMAHP was also compared with commercially available amine functionalized weak base anion exchanger, Duolite A‐7. Regeneration studies were also conducted to evaluate the reusability of the adsorbent. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Magnetic Polyacrylic Anion Exchange Resin: Preparation, Characterization and Adsorption Behavior of Humic Acid

Magnetic polyacrylic resin (R0) was prepared by suspension polymerization in the presence of γ-Fe2O3 and γ-methacryloxypropyltrimethoxysilane (γ-MPS). The obtained magnetic resin (R0) was modified sequentially by ammonolysis and alkylation to produce a magnetic weakly basic anion exchange resin (R1) and a magnetic strongly basic anion exchange resin (R2). Infrared (IR) spectra, elemental analysis, scanning electron microscopy (SEM), magnetization, Brunauer–Emmett–Teller (BET) surface area and chemical analysis were all determined to characterize these resins. The investigation of humic acid (HA) adsorption on R0, R1, and R2 showed that chemical interactions between the functional groups of the resin and HA were responsible for HA adsorption. The adsorption capacity of HA on R1 was ∼20%–60% less than that of R2, but the R1 resin was easier to regenerate with NaOH aqueous solution. A mixture of 1% NaCl and 1% NaOH was found to be highly efficient for the regeneration of both R1 and R2 resins, with desorption efficiencies measuring >90%. Pseudo-second-order model and Freundlich equation fit better for HA adsorption onto R1 and R2 than other typical kinetic and thermodynamic models, respectively. The effects of pH, coexisting salts (i.e., NaCl and Na2SO4), and recyclability were also assessed.

Investigation of macroporous weakly basic anion exchangers applicability in palladium(II) removal from acidic solutions – batch and column studies

Weakly basic anion (WBA) exchange resins applicability in palladium(II) removal from the acidic solution systems was tested. Equilibrium experiments, kinetics, effects of phase contact time, acids and sodium chloride concentrations on Pd(II) sorption were studied by means of both batch and fix-bed column methods. In this paper the analysis of the data obtained for Amberlite IRA-92, Amberlite IRA-95, Amberlite IRA-96, Dowex 66, Varion ADAM and Lewatit MP-62 was discussed and compared to those obtained for Amberlyst A-23, Amberlyst A-24, Dowex WGR-2 and Amberlyst A-21. The sorption capacity as high as 121.48 mg/g for Varion ADAM was found. The sorption process of Pd(II) on the weakly basic anion exchange resins was fast and the sorption capacities were found to be influenced by the acids and sodium chloride addition. The studies of Pd(II) uptake using the fix-bed columns confirm the greater affinity of Varion ADAM for Pd(II) than of the other weakly basic anion exchangers. Kinetics of Pd(II) follows the pseudo-second order kinetic equation.