Research on adsorption of Cr(Ⅵ) by Poly-epichlorohydrin-dimethylamine (EPIDMA) modified weakly basic anion exchange resin D301

A novel composite, EPIDMA/D301, with high adsorption capacity and particular affinity toward Cr(Ⅵ) was well prepared utilizing cationic polyelectrolyte poly-epichlorohydrin-dimethylamine (EPIDMA) impregnated in the networking pores of the styrene macroporous weak basic anion exchange resin D301. The physicochemical characteristics of EPIDMA/D301 were characterized by the Brunauer-Emmett-Teller (BET), zeta potential, FTIR, SEM-Mapping and XPS. The adsorption properties were researched via the influence of the concentration of EPIDMA, adsorbent dose, pH, the initial concentration of Cr(Ⅵ) solution, contact time and temperature. Results presented that the weakly basic anion exchange resin supported cationic polymer showed the excellent potential of removing Cr(VI) ions primarily due to the nonspecific Cr(VI) adsorption resulted from the polymeric host D301, the electrostatic attraction of amino groups fixed on the D301 matrix and the embedded EPIDMA with Cr(VI) ions and the ion exchange by the displacement of Cl^- mainly derived from EPIDMA with Cr(VI) ions. The kinetic data were best fitted by the pseudo-second-order kinetic model. The batch equilibrium data followed Langmuir isotherm model well with the maximum adsorption capacity of 194 mg g^-1 at 25 °C, which demonstrated that the styrene anion exchange resin modified with EPIDMA might be an efficient approach to eliminate potentially toxic metals.

Effect of magnetic ion exchange (MIEX®) on removal of emerging organic contaminants

In this study, the removal of nine emerging organic contaminants was investigated by using anion exchange resins. The selected compounds were carbamazepine, atrazine, simazine, estrone, bisphenol A, methylparaben, ethylparaben, propylparaben and butylparaben. Two different magnetic anionic exchanger resins were tested: MIEX^® DOC and MIEX^® GOLD. The optimal resin dose (40 mL/L) and contact time (20 min) had been previously determined. Once these optimum parameters were set, the effect of the initial concentration of contaminants on the removal efficiency of the contaminants by the resins was studied. The study was carried out using mono and multicomponent systems, with distilled water and natural waters, to which contaminants had been previously added, in order to evaluate the competitive and matrix effects. Results showed that the average removal percentages obtained with the MIEX^® DOC resin were: 51%, 61%, 68% and 80% for methyl-, ethyl-, propyl-, and butylparaben, respectively. For bisphenol A the result was similar, i.e., 66%, whereas for the rest of the compounds studied, removal efficiencies lower than 15% were obtained. The MIEX^® GOLD resin achieved lower elimination rates than the MIEX^® DOC resin in all cases.

Recovery of V(V) from complex vanadium solution using capacitive deionization (CDI) with resin/carbon composite electrode

The resin-activated carbon composite (RAC) electrodes were fabricated and applied in capacitive deionization for recovery of V(V) from complex vanadium solution. The adsorption capacity of the RAC electrode for V(V) is extremely low and the reduction of V(V) is significant in low pH solution, but the adsorbed V(V) on the electrode increases obviously and the reduction of V(V) gradually diminishes with the rise of pH. However, as the pH is increased to 10, the adsorbed V(V) on the RAC electrode declines. The higher applied potential is beneficial to the adsorption of V(V) and 1.0 V is appropriate for the adsorption. The impurities ions (Al, P and Si) are mainly adsorbed in the electric double layers on the RAC electrode and V(V) is dominantly adsorbed by the resins in the electrode. The adsorbed impurity ions can be easily removed by diluted H₂SO₄ and V(V) can be effectively eluted by 10% NaOH solution. The vanadium-bearing eluent can be recycled to recover and enrich vanadium from the complex solution. The performance of the RAC electrode keeps stable during the cyclic operation. This study may provide a promising and novel method for the recovery and separation of metals from aqueous solution.

COMPARATIVE EFFECT OF FUCOIDAN FROM ALGA FUCUS VESICULOSUS AND ITS FRACTIONS, OBTAINED BY ANION-EXCHANGE CHROMATOGRAPHY, ON CELL LINES HeLa G-63, Hep G2 AND CHANG LIVER

The aim of the present study was to compare the effect of sulfated fucopolysaccharides isolated from Fucus vesiculosus on cell lines HeLa G-63, Hep G2 and Chang liver. Native fucoidan F3 and two fractions (F3-0.5 and F3-1), obtained by anion-exchange chromatography, were analyzed using chemical methods and IR-spectroscopy. Their action on cells demonstrates that F3 and F3-1, characterized by higher content of sulfates, preferable location of sulfo-groups at C4 atom of fucose residue and low content of uronic acids, inhibit cell proliferation more efficiently. Human liver tumor cells Hep G2 appeared to be the most sensitive to fucoidan treatment whereas nonmalignant human cells Chang liver were the least sensitive.

Detection of Viruses from Bioaerosols Using Anion Exchange Resin

This protocol demonstrates a customized bioaerosol sampling method for viruses. In this system, anion exchange resin is coupled with liquid impingement-based air sampling devices for efficacious concentration of negatively-charged viruses from bioaerosols. Thus, the resin serves as an additional concentration step in the bioaerosol sampling workflow. Nucleic acid extraction of the viral particles is then performed directly from the anion exchange resin, with the resulting sample suitable for molecular analyses. Further, this protocol describes a custom-built bioaerosol chamber capable of generating virus-laden bioaerosols under a variety of environmental conditions and allowing for continuous monitoring of environmental variables such as temperature, humidity, wind speed, and aerosol mass concentration. The main advantage of using this protocol is increased sensitivity of viral detection, as assessed via direct comparison to an unmodified conventional liquid impinger. Other advantages include the potential to concentrate diverse negatively-charged viruses, the low cost of anion exchange resin (~$0.14 per sample), and ease of use. Disadvantages include the inability of this protocol to assess infectivity of resin-adsorbed viral particles, and potentially the need for the optimization of the liquid sampling buffer used within the impinger.

Characteristics of competitive uptake between Microcystin-LR and natural organic matter (NOM) fractions using strongly basic anion exchange resins

Microcystins are the most commonly occurring cyanotoxins, and have been extensively studied across the globe. In the present study, a strongly basic anion exchange resin was employed to investigate the removal of Microcystin-LR (MCLR), one of the most toxic microcystin variants. Factors influencing the uptake behavior included the MCLR and resin concentrations, resin dosage, and natural organic matter (NOM) characteristics, specifically, the charge density and molecular weight distribution of source water NOM. Equivalent background concentration (EBC) was employed to evaluate the competitive uptake between NOM and MCLR. The experimental data were compared with different mathematical and physical models and pore diffusion was determined as the rate-limiting step. The resin dose/solute concentration ratio played a key role in the MCLR uptake process and MCLR removal was attributed primarily to electrostatic attractions. Charge density and molecular weight distribution of the background NOM fractions played a major role in MCLR removal at lower resin dosages (200 mg/L ∼ 1 mL/L and below), where a competitive uptake was observed due to the limited exchange sites. Further, evidences of pore blockage and site reduction were also observed in the presence of humics and larger molecular weight organic fractions, where a four-fold reduction in the MCLR uptake was observed. Comparable results were obtained for laboratory studies on synthetic laboratory water and surface water under similar conditions. Given their excellent performance and low cost, anion exchange resins are expected to present promising potentials for applications involving the removal of removal of algal toxins and NOM from surface waters.

Tandem column isolation of zirconium-89 from cyclotron bombarded yttrium targets using an automated fluidic platform: Anion exchange to hydroxamate resin columns

The development of a tandem column purification method for the preparation of high-purity ⁸⁹Zr(IV) oxalate is presented. The primary column was a macroporous strongly basic anion exchange resin on styrene divinylbenzene co-polymer. The secondary column, with an internal volume of 33 μL, was packed with hydroxamate resin. A condition of inverted selectivity was developed, whereby the ⁸⁹Zr eluent solution for the primary column is equivalent to the ⁸⁹Zr load solution for the secondary column. The ability to transfer ⁸⁹Zr from one column to the next allows two sequential column clean-up methods to be performed prior to the final elution of the ⁸⁹Zr(IV) oxalate. This approach assures delivery of high purity ⁸⁹Zr product and assures a ⁸⁹Zr product that is eluted in a substantially smaller volume than is possible when using the traditionally-employed single hydroxamate resin column method. The tandem column purification process has been implemented into a prototype automated fluidic system. The system is configured with on-line gamma detection so column effluents can be monitored in near-real time. The automated method was tested using seven cyclotron bombarded Y foil targets. It was found that 95.1 ± 1.3% of the ⁸⁹Zr present in the foils was recovered in the secondary column elution fraction. Furthermore, elution peak analysis of several ⁸⁹Zr elution profile radiochromatograms made possible the determination of ⁸⁹Zr recovery as a function of volume; a ⁸⁹Zr product volume that contains 90% of the mean secondary column elution peak can be obtained in 0.29 ± 0.06 mL (representing 86 ± 5% of the ⁸⁹Zr activity in the target). This product volume represents a significant improvement in radionuclide product concentration over the predominant method used in the field. In addition to the reduced ⁸⁹Zr product elution volume, titrations of the ⁸⁹Zr product with deferoxamine mesylate salt across two preparatory methods resulted in mean effective specific activity (ESA) values of 279 and 340 T Bq·mmole^-1 and mean bindable metals concentrations ([M_B]) of 13.5 and 16.7 nmole·g^-1. These ESA and [M_B] values infer that the ⁸⁹Zr(IV) oxalate product resulting from this tandem column isolation method has the highest purity reported to date.

The stable oxygen isotope ratio of resin extractable phosphate derived from fresh cattle faeces

RATIONALE

Phosphorus losses from agriculture pose an environmental threat to watercourses. A new approach using the stable oxygen isotope ratio of oxygen in phosphate (δ¹⁸ O_PO4 value) may help elucidate some phosphorus sources and cycling. Accurately determined and isotopically distinct source values are essential for this process. The δ¹⁸ O_PO4 values of animal wastes have, up to now, received little attention.

METHODS

Phosphate (PO₄ ) was extracted from cattle faeces using anion resins and the contribution of microbial PO₄ was assessed. The δ¹⁸ O_PO4 value of the extracted PO₄ was measured by precipitating silver phosphate and subsequent analysis on a thermal conversion elemental analyser at 1400°C, with the resultant carbon monoxide being mixed with a helium carrier gas passed through a gas chromatography (GC) column into a mass spectrometer. Faecal water oxygen isotope ratios (δ¹⁸ O_H2O values) were determined on a dual-inlet mass spectrometer through a process of headspace carbon dioxide equilibration with water samples.

RESULTS

Microbiological results indicated that much of the extracted PO₄ was not derived directly from the gut fauna lysed during the extraction of PO₄ from the faeces. Assuming that the faecal δ¹⁸ O_H2O values represented cattle body water, the predicted pyrophosphatase equilibrium δ¹⁸ O_PO4 (Eδ¹⁸ O_PO4 ) values ranged between +17.9 and +19.9‰, while using groundwater δ¹⁸ O_H2O values gave a range of +13.1 to +14.0‰. The faecal δ¹⁸ O_PO4 values ranged between +13.2 and +15.3‰.

CONCLUSIONS

The fresh faecal δ¹⁸ O_PO4 values were equivalent to those reported elsewhere for agricultural animal slurry. However, they were different from the Eδ¹⁸ O_PO4 value calculated from the faecal δ¹⁸ O_H2O value. Our results indicate that slurry PO₄ is, in the main, derived from animal faeces although an explanation for the observed value range could not be determined.

Development of nanoscale zirconium molybdate embedded anion exchange resin for selective removal of phosphate

Development of a selective adsorbent with an enhanced removal efficiency for phosphate from wastewater is urgently needed. Here, a hybrid adsorbent of nanoscale zirconium molybdate embedded in a macroporous anion exchange resin (ZMAE) is proposed for the selective removal of phosphate. The ZMAE consists of a low agglomeration of zirconium molybdate nanoparticles (ZM NPs) dispersed within the structure of the anion exchange (AE) resin. As major results, the phosphate adsorption capacity of the ZMAE (26.1 mg-P/g) in the presence of excess sulfate (5 mM) is superior to that of the pristine AE resin (1.8 mg-P/g) although their phosphate uptake capacity was similar in the absence of sulfate and these results were supported by the high selectivity coefficient of the ZMAE toward phosphate over sulfate (S_PO4/SO4) more than 100 times compared to the pristine AE resin. This superior selective performance of the ZMAE for phosphate in the presence of sulfate ions is well explained by the role of the ZM NPs that contributed to 69% of the phosphate capacity which is based on an observation that the phosphate adsorption capacity of the ZM NPs is not affected by the presence of sulfate. In addition, the behavior of the selective phosphate removal by the ZMAE was well demonstrated by not only in the batch mode experiment with simulated Mekong river water and representative wastewater effluent but also in a column test.

Simultaneous uptake of NOM and Microcystin-LR by anion exchange resins: Effect of inorganic ions and resin regeneration

This study investigated the efficiency of a strongly basic macroporous anion exchange resin for the co-removal of Microcystin-LR (MCLR) and natural organic matter (NOM) in waters affected by toxic algal blooms. Environmental factors influencing the uptake behavior included MCLR and resin concentrations, NOM and anionic species, specifically nitrate, sulphate and bicarbonate. A860 resin exhibited an excellent adsorption capacity of 3800 μg/g; more than 60% of the MCLR removal was achieved within 10 min with a resin dosage of 200 mg/L (∼1 mL/L). Further, kinetic studies revealed that the overall removal of MCLR is influenced by both external diffusion and intra-particle diffusion. Increasing NOM concentration resulted in a significant reduction of MCLR uptake, especially at lower resin dosages, where a competitive uptake between the charged NOM fractions and MCLR was observed due to limited active sites. In addition, MCLR uptake was significantly reduced in the presence of sulphate and nitrate in the water matrix. Moreover, performance of the resin proved to be stable from one regeneration cycle to another. Approximately 80% of MCLR and 50% of dissolved organic carbon (DOC) were recovered in the regenerated brine. Evidences of resin saturation and site reduction were also observed after 2000 bed volumes (BV) of operation. For all the investigated water matrices, a resin dosage of 1000 mg/L (∼4.5 mL/L) was sufficient to lower MCLR concentration from 100 μg/L to below the World Health Organization guideline of 1 μg/L, while simultaneously providing more than 80% NOM removal.

Comparison of different methodologies for the 90Sr determination in environmental samples

The paper describes different isolation/separation and detection procedures for ⁹⁰Sr determination in the environmental samples which are routinely used in Laboratories A and B. In this context, four different methods for strontium isolation and two methods for detection were tested and compared by ⁹⁰Sr determination in proficiency test samples (water, soil, vegetation) and animal bone samples. The chromatographic isolation of Sr on Sr resin, AnaLig^®Sr01 resin gel, strong base anion exchange resins in nitrate form and combination of strong base anion exchange and Sr resin were used for the examination of the impact of sample matrix constituents on efficiency of strontium isolation (chemical yield), while Cherenkov counting of ⁹⁰Y and counting of ⁹⁰Sr(⁹⁰Y) on proportional counter were used for the quantitative ⁹⁰Sr determination. The chemical yields obtained with different isolation methods were compared with the emphasis on its influence on reliability of the ⁹⁰Sr determination in different kinds of samples. The results show that the efficiency of strontium isolation depends on type of sample and separation methodology. The strontium yield on Sr resin column decreases with the increase of Sr, Ca and Na concentration. In the presence of 1 g of Ca and 1 g of Na, the yield of 85% was obtained for 5 mg of Sr carrier and dropped below 50% with further increase of Sr and other elements. However, the yield can be increased to 75% if Na and part of Ca are separated from Sr on the anion exchange column with alcoholic solution of nitric acid and by final separation of Ca from Sr on the Sr resin column. In the presence of large amounts of Ca, Na and other elements, isolation efficiency on the Sr resin column significantly decreases in comparison with other methods. The average yield for isolation from vegetation samples on the Sr resin column is only 21%. For the soil samples the highest average yield (78%) is obtained for the isolation in the combination of anion exchange and Sr resin columns. For the isolation from bone samples the average yields over 80% are on AnaLig^®Sr01 and anion exchange resins columns, while Sr resin was not used for separation due to high content of Ca in samples. The results of the ⁹⁰Sr determination in proficiency testing (PT) samples show that the accuracy of the determination does not depend on high chemical yield but depends on accuracy of yield determination. The analysis of z-values shows that 96% of obtained z-values range from 0 to ±2 while 77% of z-values range between 0 and ± 1. Ninety percent of obtained results of ⁹⁰Sr determination deviate less than 20% from assigned values in PT provider reports. The results of ⁹⁰Sr determination in animal bone samples using different methods are in good agreement. The results obtained by Cherenkov counting in both laboratories vary from -3.1-14.5% while results obtained by determination via ⁹⁰Y and counting on i-Matic vary between -10.0 and -2.9%. These deviations are in accordance with deviations obtained with PT samples. Activity concentrations of ⁹⁰Sr in wild boar bone samples range from 4 to 30 Bq kg^-1 while in deer bone samples from 2 to 8 Bq kg^-1.

Effect of pore structure on the removal of clofibric acid by magnetic anion exchange resin

The effect of pore structure of resin on clofibric acid (CA) adsorption behavior was investigated by using magnetic anion exchange resins (ND-1, ND-2, ND-3) with increasing pore diameter by 11.68, 15.37, 24.94 nm. Resin with larger pores showed faster adsorption rates and a higher adsorption capacity because the more opened tunnels provided by larger pores benefit the CA diffusion into the resin matrix. The ion exchange by the electrostatic interactions between Cl-type resin and CA resulted in chloride releasing to the solution, and the ratio of released chloride to CA adsorption amount decreased from 0.90 to 0.65 for ND-1, ND-2 and ND-3, indicating that non-electrostatic interactions obtain a larger proportional part of the adsorption into the pores. Co-existing inorganic anions and organic acids reduced the CA adsorption amounts by the competition effect of electrostatic interaction, whereas resins with more opened pore structures weakened the negative influence on CA adsorption because of the existence of non-electrostatic interactions. 85.2% and 65.1% adsorption amounts decrease are calculated for resin ND-1 and ND-3 by the negative influence of 1 mmol L^-1 NaCl. This weaken effect of organic acid is generally depends on its hydrophobicity (Log Kow) for carboxylic acid and its ionization degree (pKb) for sulfonic acid. The resins could be reused with the slightly decreases by 1.9%, 3.2% and 5.4% after 7 cycles of regeneration, respectively for ND-1, ND-2 and ND-3, suggesting the ion exchange resin with larger pores are against its reuse by the brine solution regeneration.

Modacrylic anion-exchange fibers for Cr(VI) removal from chromium-plating rinse water in batch and flow-through column experiments

The aim of this study was to investigate Cr(VI) removal from chromium-plating rinse water using modacrylic anion-exchange fibers (KaracaronTM KC31). Batch experiments were performed with synthetic Cr(VI) solutions to characterize the KC31 fibers in Cr(VI) removal. Cr(VI) removal by the fibers was affected by solution pH; the Cr(VI) removal capacity was the highest at pH 2 and decreased gradually with a pH increase from 2 to 12. In regeneration and reuse experiments, the Cr(VI) removal capacity remained above 37.0 mg g^-1 over five adsorption-desorption cycles, demonstrating that the fibers could be successfully regenerated with NaCl solution and reused. The maximum Cr(VI) removal capacity was determined to be 250.3 mg g^-1 from the Langmuir model. In Fourier-transform infrared spectra, a Cr = O peak newly appeared at 897 cm^-1 after Cr(VI) removal, whereas a Cr-O peak was detected at 772 cm^-1 due to the association of Cr(VI) ions with ion-exchange sites. X-ray photoelectron spectroscopy analyses demonstrated that Cr(VI) was partially reduced to Cr(III) after the ion exchange on the surfaces of the fibers. Batch experiments with chromium-plating rinse water (Cr(VI) concentration = 1178.8 mg L^-1) showed that the fibers had a Cr(VI) removal capacity of 28.1-186.4 mg g^-1 under the given conditions (fiber dose = 1-10 g L^-1). Column experiments (column length = 10 cm, inner diameter = 2.5 cm) were conducted to examine Cr(VI) removal from chromium-plating rinse water by the fibers under flow-through column conditions. The Cr(VI) removal capacities for the fibers at flow rates of 0.5 and 1.0 mL min^-1 were 214.8 and 171.5 mg g^-1, respectively. This study demonstrates that KC31 fibers are effective in the removal of Cr(VI) ions from chromium-plating rinse water.

Effect of inorganic regenerant properties on pharmaceutical adsorption and desorption performance on polymer anion exchange resin

This study investigated the potential effect of four frequently used inorganic regenerant properties (i.e., ionic strength, cation type, anion type, and regeneration solution volume) on the desorption and adsorption performance of 14 pharmaceuticals, belonging to 12 therapeutic classes with different predominant chemical forms and hydrophobicities, using polymeric anion exchange resin (AER)-packed fixed-bed column tests. After preconditioning with NaCl, NaOH, or saline-alkaline (SA) solutions, all resulting mobile counterion types of AERs effectively adsorbed all 14 pharmaceuticals, where the preferential magnitude of OH^--type = Cl^- + OH^--type > Cl^--type. During regeneration, ionic strength (1 M versus 3 M NaCl) had no significant influence on desorption performance for any of the 14 pharmaceuticals, while no regenerant cation (HCl versus NaCl) or anion type (NaCl versus NaOH and SA) achieved higher desorption efficiencies for all pharmaceuticals. A volumetric increase in 1 M or 3 M NaCl solutions significantly improved the desorption efficiencies of most pharmaceuticals, irrespective of ionic strength. The results indicate that regeneration protocols, including regenerant cation type, anion type and volume, should be optimized to improve pharmaceutical removal by AERs.

Impact of ozonation, anion exchange resin and UV/H2O2 pre-treatments to control fouling of ultrafiltration membrane for drinking water treatment

The effects of ozonation, anion exchange resin (AER) and UV/H₂O₂ were investigated as a pre-treatment to control organic fouling (OF) of ultrafiltration membrane in the treatment of drinking water. It was found that high molecular weight (MW) organics such as protein and polysaccharide substances were majorly responsible for reversible fouling which contributed to 90% of total fouling. The decline rate increased with successive filtration cycles due to deposition of protein content over time. All pre-treatment could reduce the foulants of a Ultrafiltration membrane which contributed to the improvement in flux, and there was a greater improvement of flux by UV/H₂O₂ (61%) than ozonation (43%) which in turn was greater than AER (23%) treatment. This was likely due to the effective removal/breakdown of high MW organic content. AER gave greater removal of biofouling potential components (such as biodegradable dissolved organic carbon and assimilable organic carbon contents) compared to UV/H₂O₂ and ozonation treatment. Overall, this study demonstrated the potential of pre-treatments for reducing OF of ultrafiltration for the treatment of drinking water.

Adsorption behavior of benzenesulfonic acid by novel weakly basic anion exchange resins

Two novel weakly basic anion exchange resins (SZ-1 and SZ-2) were prepared via the reaction of macroporous chloromethylated polystyrene-divinylbenzene (Cl-PS-DVB) beads with dicyclohexylamine and piperidine, respectively. The physicochemical structures of the resulting resins were characterized using Fourier Transform Infrared Spectroscopy and pore size distribution analysis. The adsorption behavior of SZ-1 and SZ-2 for benzenesulfonic acid (BA) was evaluated, and the common commercial weakly basic anion exchanger D301 was also employed for comparison purpose. Adsorption isotherms and influence of solution pH, temperature and coexisting competitive inorganic salts (Na₂SO₄ and NaCl) on adsorption behavior were investigated and the optimum desorption agent was obtained. Adsorption isotherms of BA were found to be well represented by the Langmuir model. Thermodynamic parameters involving ΔH, ΔG and ΔS were also calculated and the results indicate that adsorption is an exothermic and spontaneous process. Enhanced selectivity of BA sorption over sulfate on the two novel resins was observed by comparison with the commercial anion exchanger D301. The fact that the tested resins loaded with BA can be efficiently regenerated by NaCl solution indicates the reversible sorption process. From a mechanistic viewpoint, this observation clearly suggests that electrostatic interaction is the predominant adsorption mechanism. Furthermore, results of column tests show that SZ-1 possesses a better adsorption property than D301, which reinforces the feasibility of SZ-1 for potential industrial application.

Desulfurization: Critical step towards enhanced selenium removal from industrial effluents

Selenium (Se) removal from synthetic solutions and from real Flue Gas Desulfurization (FGD) wastewater generated by a coal-fired power plant was studied for the first time using a commercial iron oxide impregnated strong base anion exchange resin, Purolite^® FerrIX A33E. In synthetic solutions, the resin showed high affinity for selenate and selenite, while sulfate exhibited a strong competition for both oxyanions. The FGD wastewater investigated is a complex system that contains Se (∼1200 μg L^-1), SO₄^2- (∼1.1 g L^-1), Cl^- (∼9.5 g L^-1), and Ca²⁺ (∼5 g L^-1), alongside a broad spectrum of toxic trace metals including Cd, Cr, Hg, Ni, and Zn. The resin performed poorly against Se in the raw FGD wastewater and showed moderate to good removal of several trace elements such as Cd, Cr, Hg, and Zn. In FGD effluent, sulfate was identified as a powerful competing anion for Se, having high affinity for the exchange active sites of the resin. The desulfurization of the FGD effluent using BaCl₂ led to the increase in Se removal from 3% (non-desulfurized effluent) to 80% (desulfurized effluent) by combined precipitation and ion exchange treatment. However, complete desulfurization using equimolar BaCl₂ could not be achieved due to the presence of bicarbonate that acts as a sulfate competitor for barium. In addition to selenium and sulfate removal, several toxic metals were efficiently removed (Cd: 91%; Cr: 100%; Zn: 99%) by the combined (desulfurization and ion exchange) treatment.

Mg/Al double-metal hydroxide regeneration of anion exchange resin by electric field intensification

Fouled anion exchange resins were regenerated by electric field intensification of Mg/Al double-metal hydroxides. Regenerative experiments were performed with varying voltages (10-30 V) and dosages of Mg/Al hydroxides (0.045-0.135 mol and 0.015-0.045 mol, respectively) for 1-5 h. Optimal results were obtained under the following regenerative conditions: 20 V, 4 h, and 0.09/0.03 mol of Mg/Al hydroxides. The maximum regenerative capacity of resins was increased to 41.07%. The regenerative mechanism was presented by Fourier-transform infrared spectrum of resins and Mg/Al hydroxides, and the regenerative degree was analyzed with respect to conductivity, pH value, and electric current. Mg/Al hydroxides were also recycled after the regeneration. This method was proven to be cost-effective and environmentally friendly.

Preparation of nitrate-selective porous magnetic resin and assessment of its performance in removing nitrate from groundwater

Nitrate-selective, porous magnetic anion-exchange resin (NS-PMAER) with enhanced affinity and higher selectivity for nitrate was synthesized, characterized and its performance in nitrate removal was investigated. The results show that NS-PMAER consists of spherical particles with an average size of 200 μm. It has mean pore diameter, total pore volume, and BET specific surface area of 21.38 nm, 0.3605 cm³/g, and 67.455 m²/g, respectively. The specific saturation magnetization of NS-PMAER was about 10.79 emu/g. Fourier transform infrared spectrometer (FTIR) and X-ray photoelectron spectroscopy (XPS) results indicate that NS-PMAER has selectivity for nitrate higher than that of MIEX® resin; its coefficients of selectivity toward nitrate for nitrate and sulfate are 20.978 and 6.769, respectively, higher than those of MIEX® resin (1.256 and 4.342, respectively). Its working exchange capacity was 72.41 mg/mL. Column-exchange experiments' results suggest that it could be easily regenerated using 1.5 mol/L sodium chloride solution for a contact time of 30 min. Its recovery rate stayed at > 95% even after five rounds of recycling. Results of the pilot test indicate that NS-PMAER could effectively remove nitrate in groundwater, and ensure that nitrate concentrations of effluent to meet the guideline limit for drinking water by the World Health Organization.

Removal of protein-bound and unbound unconjugated bilirubin by perfusion of plasma through an anion-exchange resin in a case of Crigler-Najjar syndrome type I

Background: Patients with Crigler-Najjar syndrome, type I (CNS-I) have an inherited absence of hepatocellular bilirubin uridine diphosphate-glucuronosyltransferase activity, which results in severe unconjugated hyperbilirubinaemia, often causing kernicterus and death in infancy or childhood.

Methods: Our patient is a 19-year-old Japanese man with CNS-I diagnosed by the complete absence of the hepatocellular enzyme in a liver biopsy and genotyping. The efficacies of the removal of protein-bound (PBB) and unbound (UB) unconjugated bilirubin by phototherapy, plasma perfusion and liver transplantation were compared in the patient.

Results: At the age of 5 years, phototherapy treatment reduced the patient's PBB by 21% and UB by 34%, and 98% of the bilirubin produced daily was removed. At the age of 16 years, plasma perfusion combined with nightly phototherapy completely removed the daily production of bilirubin; however, by 24 h post-treatment, the PBB and UB were again increased. Apparently, these treatments were effective in reducing PBB and UB, but the effect was only temporary. Following liver transplantation, PBB and UB decreased to normal concentrations.

Conclusions: Liver transplantation as a potential cure should be performed at a younger age, particularly in confirmed CNS-I cases for which reliable effects of phototherapy cannot be guaranteed.

The oxidative degradation of polystyrene resins on the removal of Cr(VI) from wastewater by anion exchange

Cr(VI) is a powerful oxidant and is capable of oxidizing most of the organic materials. Therefore, it is possible for Cr(VI) to oxidize the polymeric resins and change the sorption properties of the resins on the removal of Cr(VI) from wastewater by anion exchange. In this study, three polystyrene resins (D201, D202, and D301) with different functional groups (-N(+)(CH3)3, -N(+)(CH3)2(C2H4OH), and N(CH3)2) were assessed on oxidation stability for Cr(VI) removal from wastewater in fixed-bed column experiments. After a 10-cycle operation, due to the oxidation of the resin, the sorption capacity of D201, D202, and D301 resins decreased by 23.5, 29.3, and 17.3%, when approximately 20-34%, 31-50%, and 18-30% of Cr(VI) was reduced to Cr(III) during each cycle respectively. The results of the Fourier transform infrared spectroscopy (FT-IR) showed that both the cleavage of CN and the formation of CO bonds occurred on the polystyrene resins during the Cr(VI) removal process. The resin simulation experiments further validated the oxidation of CC and CN bonds connected with phenethyl groups. Based upon the results from column operations and the resin simulated experiments, the oxidation mechanism of the polystyrene resin was proposed.

One-step chromatographic procedure for purification of B-phycoerythrin from Porphyridium cruentum

B-phycoerythrin (B-PE) was separated and purified from microalga Porphyridium cruentum using one-step chromatographic method. Phycobiliproteins in P. cruentum was extracted by osmotic shock and initially purified by ultrafiltration. Further purification was carried out with a SOURCE 15Q exchange column and analytical grade B-PE was obtained with a purity ratio (A545/A280) of 5.1 and a yield of 68.5%. It showed a double absorption peaks at 545 nm and 565 nm and a shoulder peak at 498 nm, and displayed a fluorescence emission maximum at 580 nm. The analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed a bulky band between 18 and 20 kDa which could be assigned to subunits α and β and a low intensity band of 27 kDa assigned to γ subunit. Our protocol provides attractive alternative to consider for the purification procedure to obtain analytical grade B-PE at commercial level.

Use of strong anion exchange resins for the removal of perfluoroalkylated substances from contaminated drinking water in batch and continuous pilot plants

In recent years abnormally high levels of perfluoroalkylated substances (PFAS) have been detected both in surface and underground water sampled in an area covering approximately 150 square kilometers in the Veneto region (Italy) indicating the presence of a pollution point source (fluorochemicals production plant). Adsorption on granular activated carbon is an emergency measure which is poorly effective requiring frequent replacement. This work focuses on the application of three strong anion exchange resins (Purolite® A520E, A600E and A532E) for the removal of traces of PFOA, PFOS, PFBA and PFBS (concentration of hundreds of ng L(-1)) from drinking water. This technology is attractive for the possibility of reusing resins after an in-situ regeneration step. A strong relationship between the hydrophobicity of the exchange functional group of the resin and its capacity in removing PFAS exists. A600E (non hydrophobic) and A520E (fairly hydrophobic) show a reduced sorption capacity compared to A532E (highly hydrophobic). While A600E and A520E can be regenerated with solvent-less dilute solutions of non-toxic NH4Cl and NH4OH, A532E requires concentrated solutions of methanol or ethanol and 1% NH4Cl and for the sake of this work it was regarded as non-regenerable. The volume of regeneration effluents requiring incineration can be efficiently reduced by more than 96.5% by using reverse osmosis coupled with under-vacuum evaporation. Transmission electron analysis on saturated resins showed that large molecular macro-aggregates of PFAS can form in the intraparticle pores of resin indicating that ion exchange is not the only mechanism involved in PFAS removal.

Chemical fractionation and speciation modelling for optimization of ion-exchange processes to recover palladium from industrial wastewater

Palladium is used in several industrial applications and, given its high intrinsic value, intense efforts are made to recover the element. In this hydrometallurgic perspective, ion-exchange (IEX) technologies are principal means. Yet, without incorporating the chemical and physical properties of the Pd present in real, plant-specific conditions, the recovery cannot reach its technical nor economic optimum. This study characterized a relevant Pd-containing waste stream of a mirror manufacturer to provide input for a speciation model, predicting the Pd speciation as a function of pH and chloride concentration. Besides the administered neutral PdCl2 form, both positively and negatively charged [PdCln](2-n) species occur depending on the chloride concentration in solution. Purolite C100 and Relite 2AS IEX resins were selected and applied in combination with other treatment steps to optimize the Pd recovery. A combination of the cation and anion exchange resins was found successful to quantitatively recover Pd. Given the fact that Pd was also primarily associated with particles, laboratory-scale experiments focused on physical removal of the Pd-containing flow were conducted, which showed that particle-bound Pd can already be removed by physical pre-treatment prior to IEX, while the ionic fraction remains fully susceptible to the IEX mechanism.

Enhanced DOC removal using anion and cation ion exchange resins

Hardness and DOC removal in a single ion exchange unit operation allows for less infrastructure, is advantageous for process operation and depending on the water source, could enhance anion exchange resin removal of dissolved organic carbon (DOC). Simultaneous application of cationic (Plus) and anionic (MIEX) ion exchange resin in a single contact vessel was tested at pilot and bench scales, under multiple regeneration cycles. Hardness removal correlated with theoretical predictions; where measured hardness was between 88 and 98% of the predicted value. Comparing bench scale DOC removal of solely treating water with MIEX compared to Plus and MIEX treated water showed an enhanced DOC removal, where removal was increased from 0.5 to 1.25 mg/L for the simultaneous resin application compared to solely applying MIEX resin. A full scale MIEX treatment plant (14.5 MGD) reduced raw water DOC from 13.7 mg/L to 4.90 mg/L in the treated effluent at a bed volume (BV) treatment rate of 800, where a parallel operation of a simultaneous MIEX and Plus resin pilot (10 gpm) measured effluent DOC concentrations of no greater than 3.4 mg/L, even at bed volumes of treatment 37.5% greater than the full scale plant. MIEX effluent compared to simultaneous Plus and MIEX effluent resulted in differences in fluorescence intensity that correlated to decreases in DOC concentration. The simultaneous treatment of Plus and MIEX resin produced water with predominantly microbial character, indicating the enhanced DOC removal was principally due to increased removal of terrestrially derived organic matter. The addition of Plus resin to a process train with MIEX resin allows for one treatment process to remove both DOC and hardness, where a single brine waste stream can be sent to sewer at a full-scale plant, completely removing lime chemical addition and sludge waste disposal for precipitative softening processes.