Development and validation of a novel modeling framework integrating ion exchange and resin regeneration for water treatment

Models have been developed to simulate the process of ion exchange for water treatment. However the modeling of resin regeneration process, which can predict regeneration efficiency and residual stream for determining technology sustainability, was not incorporated into previous models. Therefore a model integrating both ion exchange and resin regeneration considering regeneration efficiency is needed for evaluating and improving ion exchange technology. This study developed an integrated model aiming to simulate ion exchange and resin regeneration in different configurations (fixed bed, fluidized bed) for the first time. The integrated model has been validated via comparing model predictions with experimental data. The impacts of dimensionless groups (i.e. the Péclet number, the diffusion modulus, and the Biot number) on ion exchange breakthrough curve have been analyzed using this model. In addition, this integrated model has been used to optimize the regeneration frequency to improve the overall performance of ion exchange. It demonstrated this integrated model could be a useful tool for further studies in ion exchange technology.

Synthesis of biodiesel from pongamia oil using heterogeneous ion-exchange resin catalyst

Biodiesel is a clean-burning renewable substitute fuel for petroleum. Biodiesel could be effectively produced by transesterification reaction of triglycerides of vegetable oils with short-chain alcohols in the presence of homogeneous or heterogeneous catalysts. Conventionally, biodiesel manufacturing processes employ strong acids or bases as catalysts. But, separation of the catalyst and the by-product glycerol from the product ester is too expensive to justify the product use as an automobile fuel. Hence heterogeneous catalysts are preferred. In this study, transesterification of pongamia oil with ethanol was performed using a solid ion-exchange resin catalyst. It is a macro porous strongly basic anion exchange resin. The process parameters affecting the ethyl ester yield were investigated. The reaction conditions were optimized for the maximum yield of fatty acid ethyl ester (FAEE) of pongamia oil. The properties of FAEE were compared with accepted standards of biodiesel. Engine performance was also studied with pongamia oil diesel blend and engine emission characteristics were observed.

Effect of long-term organic removal on ion exchange properties and performance during sewage tertiary treatment by conventional anion exchange resins

This study evaluated the long-term dissolved organic matter (DOM), phosphorus and nitrogen removal performance of a commercially available conventional anion exchange resin (AER) from actual secondary effluent (SE) in a sewage treatment plant based on a pilot-scale operation (2.2 m(3) d(-1), 185 cycles, 37,000 bed volume, 1.5 years). Particular emphasis was given to the potential effect of DOM fouling on the ion exchange properties and performance during the long-term operation. Despite the large range of COD (15.6-33.5 mg L(-1)), BOD5 (3.0-5.6 mg L(-1)), DOC (6.5-24.2 mg L(-1)), and UV254 (UV absorption at 254 nm) (0.108-0.229 cm(-1)) levels in the SE, the removal efficiencies of the AER for the aforementioned parameters were 43±12%, 46±15%, 45±9%, and 72±4%, respectively. Based on three-dimensional fluorescence excitation-emission matrix data, i.e., the fluorescence intensities of four regions (peaks A-D), all organic components of the SE were effectively removed (peak A 74%, peak B 48%, peak C 55%, and peak D 45%) following the adsorption. The AER effluent still has considerable polycyclic aromatic hydrocarbons' ecological hazard on freshwater fishes when they were significantly removed from SE. The obvious DOM fouling on the AER, identified by color change, had no significant influence on the long-term removal of the representative inorganic anions (averaging 95±4% phosphate, 100±0% SO4(2-), and 62±17% NO3(-)) and AER properties (including total exchange capacity, moisture content, and true density). The conventional AER can produce high quality reclaimed water from SE at a low operational cost.

Determination of low-level radiostrontium, with emphasis on in situ pre-concentration of Sr from large volume of freshwater sample using Powdex resin

An improved analytical method was developed for determining of low levels of radiostrontium in environmental freshwater samples. Emphasis was placed to the in situ pre-concentration of radiostrontium with Powdex resin in large volumes (100-300 L) of freshwater samples from many locations without using of deleterious substances such as NaOH and mineral acids. Measuring electric conductivity (EC) of water samples enabled the estimation of the amount of Powdex resin required for quantitative recovery of Sr from the large water samples in the field. The Powdex resin that adsorbed Sr was brought back to the laboratory, and Sr adsorbed in the resin was eluted by 8 M HNO3 together with Sr carrier added. Strontium was radiochemically separated by the cation exchange method for β counting after removal of most of the Ca using Ca(OH)2 precipitation. Through the procedure the Sr chemical yield was 88% on average. This analytical method was verified by analyzing 170 L of water samples with different salinity values, to which a known amount of (90)Sr was added. The detection limits of (90)Sr activities obtained using the 170 L water samples was estimated to be approximately 0.1 mBq L(-1) for a counting time of 100 min. The method was also applied to environmental samples collected from Ibaraki and Fukushima prefectures; their (90)Sr activities ranged from 0.16 to 0.93 mBq L(-)(1).

New gel-like polymers as selective weak-base anion exchangers

A group of new anion exchangers, based on polyamine podands and of excellent ion-binding capacity, were synthesized. The materials were obtained in reactions between various poly(ethyleneamines) with glycidyl derivatives of cyclotetrasiloxane. The final polymeric, strongly cross-linked materials form gel-like solids. Their structures and interactions with anions adsorbed were studied by spectroscopic methods (CP-MAS NMR, FR-IR, UV-Vis). The sorption isotherms and kinetic parameters were determined for 29 anions. Materials studied show high ion capacity and selectivity towards some important anions, e.g., selenate(VI) or perrhenate.

Integrating tunable anion exchange with reverse osmosis for enhanced recovery during inland brackish water desalination

For inland brackish water desalination by reverse osmosis or RO, concentrate or reject disposal poses a major challenge. However, enhanced recovery and consequent reduction in the reject volume using RO processes is limited by the solubility of ions present in the feedwater. One of the most common and stubborn precipitate formed during desalination is calcium sulfate. Reducing or eliminating the presence of sulfate would allow the process to operate at higher recoveries without threat to membrane scaling. In this research, this goal is accomplished by using an appropriate mixture of self-regenerating anion exchange resins that selectively remove and replace sulfate by chloride prior to the RO unit. Most importantly, the mixed bed of anion exchange resins is self-regenerated with the reject brine from the RO process, thus requiring no addition of external chemicals. The current work demonstrates the reversibility of the hybrid ion exchange and RO (HIX-RO) process with 80% recovery for a brackish water composition representative of groundwater in San Joaquin Valley in California containing approximately 5200 mg/L of total dissolved solids or TDS. Consequently, the reject volume can be reduced by 50% without the threat of sulfate scaling and use of antiscaling chemicals can be eliminated altogether. By appropriately designing or tuning the mixed bed of anion exchange resins, the process can be extended to nearly any composition of brackish water for enhanced recovery and consequent reduction in the reject volume.

Integration of ion-exchange and nanofiltration processes for recovering Cr(III) salts from synthetic tannery wastewater

This study aims to investigate the possibility of integrating both ion-exchange (IX) and nanofiltration (NF) processes for the recovery of Cr(III) salts from a synthetic solution prepared with concentrations of Cr(III), [Formula: see text] and Cl(-) in the range of industrial effluents of tanneries. Ion exchange should be used as a pre-treatment for uptaking Cl(-) ions from the effluent, and thereafter the treated solution is fed to an NF unit to recover chromium sulphate salt for reuse in the tanning bath. The strong anionic resin Diaion PA316 was selected for evaluating chloride-sulphate ion-exchange equilibrium, with respect to mass of resin, NaCl concentration, temperature and ratio [Formula: see text]. It was observed that the separation factor, [Formula: see text], depends on the total electrolyte concentration and the ratio [Formula: see text] plays a role as well. Moreover, it was determined that the resin prefers sulphate over chloride since [Formula: see text] is less than 1. The performance of the NF process is dependent on [Formula: see text] and the rejection of Cr(III) may decrease from 90% to 70% as the ratio increases from 0.5 to 2. Regarding the integration of both IX and NF, the feed solution after treatement with the resin was fed to NF where the ratio of [Formula: see text] led to the best operating conditions for this process (90% of Cr(III) rejection and up to 77% for [Formula: see text] ions). This strategy may be considered as a sustainable approach since it permits to obtain a solution enriched in Cr(III) salt for reuse in the tanning process, thus contributing to environmental protection.

High-performance liquid chromatography separation of cis-trans anthocyanin isomers from wild Lycium ruthenicum Murr. employing a mixed-mode reversed-phase/strong anion-exchange stationary phase

The cis-trans isomerism is a common phenomenon for acylated anthocyanins. Nevertheless, few studies reported effective methods for the preparation of isomeric anthocyanins from natural products. In this work, a high-performance liquid chromatography (HPLC) method was developed to efficiently purify anthocyanin isomers from Lycium ruthenicum Murr. based on a mixed-mode reversed-phase/strong anion-exchange column (named XCharge C8SAX). Four commercially available columns were evaluated with a pair of isomeric anthocyanins, and the results demonstrated that the XCharge C8SAX column exhibited improved selectivity and column efficiency for the isomers. The chromatographic parameters, including pH, organic content, and ionic strength, were investigated. Optimal separation quality for the anthocyanin isomers was achieved on the XCharge C8SAX column. Six pure anthocyanins, including two pairs of cis-trans isomeric anthocyanins with one new anthocyanin, were purified from L. ruthenicum and identified. All of the results indicated that this method is an effective way to separate anthocyanins, especially for cis-trans isomers.

Enhanced coagulation with powdered activated carbon or MIEX secondary treatment: a comparison of disinfection by-product formation and precursor removal

The removal of both organic and inorganic disinfection by-product (DBP) precursors prior to disinfection is important in mitigating DBP formation, with halide removal being particularly important in salinity-impacted water sources. A matrix of waters of variable alkalinity, halide concentration and dissolved organic carbon (DOC) concentration were treated with enhanced coagulation (EC) followed by anion exchange (MIEX resin) or powdered activated carbon (PAC) and the subsequent disinfection by-product formation potentials (DBP-FPs) assessed and compared to DBP-FPs for untreated samples. Halide and DOC removal were also monitored for both treatment processes. Bromide and iodide adsorption by MIEX treatment ranged from 0 to 53% and 4-78%, respectively. As expected, EC and PAC treatments did not remove halides. DOC removal by EC/PAC was 70 ± 10%, while EC/MIEX enabled a DOC removal of 66 ± 12%. Despite the halide removals achieved by MIEX, increases in brominated disinfection by-product (Br-DBP) formation were observed relative to untreated samples, when favourable Br:DOC ratios were created by the treatment. However, the increases in formation were less than what was observed for the EC/PAC treated waters, which caused large increases in Br-DBP formation when high Br-DBP-forming water quality conditions occurred. The formation potential of fully chlorinated DBPs decreased after treatment in all cases.

Kinetics analysis of zinc sorption in fixed bed column using a strongly basic anionic exchange resin

The aim of this study was to examine the capacity of anionic resins to remove zinc as zinc chloride complexes in fixed bed. The applicability of the kinetics models and the characteristics of the bed (sorption capacity, breakthrough curve, depth of the adsorption zone) were taken into account. The influence of the process parameters, such as resin quantity (bed height) and zinc initial concentration, on the removal process was also considered. The obtained results (Amberlite IRA410) were analyzed using sorption kinetic models such as Thomas, Adam-Bohart, and Clark, by linear regression analysis. Similarly, the concept of the mass transfer zone was applied in order to properly design the fixed bed adsorption process. By comparing various resins, the following series was depicted based on sorption capacities: Amberlite IRA410>Purolite A103S>Purolite NRW700>Purolite A400MBOH. The experimental data were in good agreement with the Clark model, while for the other models, lower correlation coefficients were obtained under the same experimental conditions. The MTZ height and rate of movement increased with increasing initial concentration.

Ion-exchange selectivity of diclofenac, ibuprofen, ketoprofen, and naproxen in ureolyzed human urine

This research advances the knowledge of ion-exchange of four non-steroidal anti-inflammatory drugs (NSAIDs) - diclofenac (DCF), ibuprofen (IBP), ketoprofen (KTP), and naproxen (NPX) - and one analgesic drug-paracetamol (PCM) - by strong-base anion exchange resin (AER) in synthetic ureolyzed urine. Freundlich, Langmuir, Dubinin-Astakhov, and Dubinin-Radushkevich isotherm models were fit to experimental equilibrium data using nonlinear least squares method. Favorable ion-exchange was observed for DCF, KTP, and NPX, whereas unfavorable ion-exchange was observed for IBP and PCM. The ion-exchange selectivity of the AER was enhanced by van der Waals interactions between the pharmaceutical and AER as well as the hydrophobicity of the pharmaceutical. For instance, the high selectivity of the AER for DCF was due to the combination of Coulombic interactions between quaternary ammonium functional group of resin and carboxylate functional group of DCF, van der Waals interactions between polystyrene resin matrix and benzene rings of DCF, and possibly hydrogen bonding between dimethylethanol amine functional group side chain and carboxylate and amine functional groups of DCF. Based on analysis of covariance, the presence of multiple pharmaceuticals did not have a significant effect on ion-exchange removal when the NSAIDs were combined in solution. The AER reached saturation of the pharmaceuticals in a continuous-flow column at varying bed volumes following a decreasing order of DCF > NPX ≈ KTP > IBP. Complete regeneration of the column was achieved using a 5% (m/m) NaCl, equal-volume water-methanol solution. Results from multiple treatment and regeneration cycles provide insight into the practical application of pharmaceutical ion-exchange in ureolyzed urine using AER.

Applications and limits of theoretical adsorption models for predicting the adsorption properties of adsorbents

The objective of this study is to evaluate the applicability of adsorption models for predicting the properties of adsorbents. The kinetics of the adsorption of NO3- ions on a PP-g-AA-Am non-woven fabric have been investigated under equilibrium conditions in both batch and fixed bed column processes. The adsorption equilibrium experiments in the batch process were carried out under different adsorbate concentration and adsorbent dosage conditions and the results were analyzed using adsorption isotherm models, energy models, and kinetic models. The results of the analysis indicate that the adsorption occurring at a fixed adsorbate concentration with a varying adsorbent dosage occur more easily compared to those under a fixed adsorbent dosage with a varying adsorbate concentration. In the second part of the study, the experimental data obtained using fixed bed columns were fit to Bed Depth Service Time, Bohart-Adams, Clark, and Wolborska models, to predict the breakthrough curves and determine the column kinetic parameters. The adsorption properties of the NO3- ions on the PP-g-AA-Am non-woven fabric were differently described by different models for both the batch and fixed bed column process. Therefore, it appears reasonable to assume that the adsorption properties were dominated by multiple mechanisms, depending on the experimental conditions.

Fundamental aspects related to batch and fixed-bed sulfate sorption by the macroporous type 1 strong base ion exchange resin Purolite A500

Acid mine drainage is a natural process occurring when sulfide minerals such as pyrite are exposed to water and oxygen. The bacterially catalyzed oxidation of pyrite is particularly common in coal mining operations and usually results in a low-pH water polluted with toxic metals and sulfate. Although high sulfate concentrations can be reduced by gypsum precipitation, removing lower concentrations (below 1200 mg/L) remains a challenge. Therefore, this work sought to investigate the application of ion exchange resins for sulfate sorption. The macroporous type 1 strong base IX resin Purolite A500 was selected for bath and fixed-bed sorption experiments using synthetic sulfate solutions. Equilibrium experiments showed that sulfate loading on the resin can be described by the Langmuir isotherm with a maximum uptake of 59 mg mL-resin(-1). The enthalpy of sorption was determined as +2.83 kJ mol(-1), implying an endothermic physisorption process that occurred with decreasing entropy (-15.5 J mol(-1).K(-1)). Fixed-bed experiments were performed at different bed depths, flow rates, and initial sulfate concentrations. The Miura and Hashimoto model predicted a maximum bed loading of 25-30 g L-bed(-1) and indicated that both film diffusion (3.2 × 10(-3) cm s(-1) to 22.6 × 10(-3) cm s(-1)) and surface diffusion (1.46 × 10(-7) cm(2) s(-1) to 5.64 × 10(-7) cm(2) s(-1)) resistances control the sorption process. It was shown that IX resins are an alternative for the removal of sulfate from mine waters; they ensure very low residual concentrations, particularly in effluents where the sulfate concentration is below the gypsum solubility threshold.

Aminoglycoside antibiotic-derived anion-exchange microbeads for plasmid DNA binding and in situ DNA capture

Plasmid DNA (pDNA) therapeutics are being investigated for gene therapy and DNA vaccines against diseases including cancer, cystic fibrosis and AIDS. In addition, several applications in modern biotechnology require pDNA for transient protein production. Here, we describe the synthesis, characterization, and evaluation of microbeads ("Amikabeads") derived from the aminoglycoside antibiotic amikacin for pDNA binding and in situ DNA capture from mammalian cells. The parental aminoglycoside-derived microbeads (Amikabeads-P) acted as anion-exchange materials, and demonstrated high capacities for binding pDNA. Binding of pDNA was significantly enhanced following quaternization of the amines on the microbeads (Amikabeads-Q). Amikabeads were further employed for the disruption and extraction of DNA from mammalian cells, indicating their utility for in situ DNA capture. Our results indicate that Amikabeads are a novel material, with multiple reactive groups for further conjugation, and can have several applications in plasmid DNA biotechnology.

Dissolved organic matter removal using magnetic anion exchange resin treatment on biological effluent of textile dyeing wastewater

This study investigated the removal of dissolved organic matter (DOM) from real dyeing bio-treatment effluents (DBEs) with the use of a novel magnetic anion exchange resin (NDMP). DOMs in two typical DBEs were fractionized using DAX-8/XAD-4 resin and ultrafiltration membranes. The hydrophilic fractions and the low molecular weight (MW) (<3kDa) DOM fractions constituted a major portion (>50%) of DOMs for the two effluents. The hydrophilic and low MW fractions of both effluents were the greatest contributors of specific UV254 absorbance (SUVA254), and the SUVA254 of DOM fractions decreased with hydrophobicity and MW. Two DBEs exhibited acute and chronic biotoxicities. Both acute and chronic toxicities of DOM fractions increased linearly with the increase of SUVA254 value. Kinetics of dissolved organic carbon (DOC) removal via NDMP treatment was performed by comparing it with that of particle active carbon (PAC). Results indicated that the removal of DOC from DBEs via NDMP was 60%, whereas DOC removals by PAC were lower than 15%. Acidic organics could be significantly removed with the use of NDMP. DOM with large MW in DBE could be removed significantly by using the same means. Removal efficiency of NDMP for DOM decreased with the decrease of MW. Compared with PAC, NDMP could significantly reduce the acute and chronic bio-toxicities of DBEs. NaCl/NaOH mixture regenerants, with selected concentrations of 10% NaCl (m/m)/1% NaOH (m/m), could improve desorption efficiency.

A new polymer-based laccase for decolorization of AO7: long-term storage and mediator reuse

To address the bottlenecks of laccase-based catalysis, i.e., poor long-term stability and potential secondary pollution caused by synthetic mediator, we fabricated a new biocatalyst (N-PS-Lac) through adsorption of laccase onto polystyrene anion exchangers (N-PS) binding quaternary ammonium groups. After 2-year storage, the residual activity of N-PS-Lac remained as high as 101.7%, while that for native laccase was only 14.6%. Also, N-PS-Lac exhibited improved durability against pH variation and thermal treatment at 60°C. Gaussian curve fitting of FT-IR spectra indicated that laccase conformation of N-PS-Lac was rigidified, possibly because of the host geometric restriction and the host-laccase electrostatic attraction. A two-step method, i.e., adsorption of an azo dye AO7 by N-PS and then ectopic degradation by the immobilized laccase, was proposed to reuse the mediator HOBT for seven cyclic runs, where N-PS-Lac kept the constant decolorization efficiency. AO7 solution was detoxified completely after decolorization by the two-step method.

Understanding and modeling removal of anionic organic contaminants (AOCs) by anion exchange resins

Ionic organic contaminants (OCs) are a growing concern for water treatment and the environment and are removed inefficiently by many existing technologies. This study examined removal of anionic OCs by anion exchange resins (AXRs) as a promising alternative. Results indicate that two polystyrene AXRs (IRA910 and IRA96) have higher sorption capacities and selectivity than a polyacrylate resin (A860). For the polystyrene resins, selectivity follows: phenolates ≥ aromatic dicarboxylates > aromatic monocarboxylates > benzenesulfonate > aliphatic carboxylates. This trend can be explained based on hydration energy, the number of exchange groups, and aromaticity and hydrophobicity of the nonpolar moiety (NPM) of the anions. For A860, selectivity only varies within a narrow range (0.13-1.64). Despite the importance of the NPM of the anions, neutral solutes were sorbed much less, indicating synergistic combinations of electrostatic and nonelectrostatic interactions in the overall sorption. By conducting multiple linear regression between Abraham's descriptors and nature log of selectivity, induced dipole-related interactions and electrostatic interactions were found to be the most important interaction forces for sorption of the anions, while solute H-bond basicity has a negative effect. A predictive model was then developed for carboxylates and phenolates based on the poly parameter linear free energy relationships established for a diverse range of 16 anions and 5 neutral solutes, and was validated by accurate prediction of sorption of five test solutes within a wide range of equilibrium concentrations and that of benzoate at different pH.

Simultaneous removal of dissolved organic matter and bromide from drinking water source by anion exchange resins for controlling disinfection by-products

Anion exchange resins (AERs) with different properties were evaluated for their ability to remove dissolved organic matter (DOM) and bromide, and to reduce disinfection by-product (DBP) formation potentials of water collected from a eutrophic surface water source in Japan. DOM and bromide were simultaneously removed by all selected AERs in batch adsorption experiments. A polyacrylic magnetic ion exchange resin (MIEX®) showed faster dissolved organic carbon (DOC) removal than other AERs because it had the smallest resin bead size. Aromatic DOM fractions with molecular weight larger than 1600 Da and fluorescent organic fractions of fulvic acid- and humic acid-like compounds were efficiently removed by all AERs. Polystyrene AERs were more effective in bromide removal than polyacrylic AERs. This result implied that the properties of AERs, i.e. material and resin size, influenced not only DOM removal but also bromide removal efficiency. MIEX® showed significant chlorinated DBP removal because it had the highest DOC removal within 30 min, whereas polystyrene AERs efficiently removed brominated DBPs, especially brominated trihalomethane species. The results suggested that, depending on source water DOM and bromide concentration, selecting a suitable AER is a key factor in effective control of chlorinated and brominated DBPs in drinking water.

Improving Gluconobacter oxydans performance in the in situ removal of the inhibitor for asymmetric resolution of racemic 1-phenyl-1,2-ethanediol

Gluconobacter oxydans DSM2003 was used to catalyze the oxidation of racemic 1-phenyl-1,2-ethanediol (PED) for the production of (S)-enantiomer. The oxidative product mandelic acid produced strong inhibition to this reaction and largely reduced the activity of biocatalyst, which was the key problem in the reaction. In order to overcome this bottleneck, an anion exchange resin was selected and introduced as adsorbent for the in situ removal of the inhibitor from the reaction system. This method increased the substrate concentration from 12 to 60 g/L and the yield of (S)-PED by approximately five times from 4.9 g/L, on the premise that the enantiomeric excess (ee) value of (S)-PED remained above 96% and the reaction time was no more than 20 h. Moreover, the final space-time yield was over 1.2g/L/h, which was higher than that reported from previous studies.

[Effects and mechanism on removing organics and reduction of membrane fouling using granular macro-porous anion exchange resin in drinking water treatment]

A granular macro-porous anion exchange resin combined with coagulation was used as pretreatment of microfiltration membrane, and their effects and mechanism on removing organics and reduction of membrane fouling were evaluated. The results showed that resin could be effective in removing organics with medium and small molecular weight ( Mr) but ineffective in removing organics with large Mr, while couagulation could significantly remove organics with large Mr, with a limited removal for organics with medium and small Mr. Using resin alone as pretreatment could be effective in removal of organics but limited in reduction of membrane fouling. With combination of coagulation and resin as pretreatment of microfiltration, not only organics could be removed effectively, but also membrane fouling could be reduced.

Kinetic study of the removal of dimethyl phthalate from an aqueous solution using an anion exchange resin

Phthalate acid esters are becoming an important class of pollutants in wastewaters. This study addresses the kinetics of removal of dimethyl phthalate (DMP) using the anion exchange resin D201-OH from an aqueous solution. The effects of various factors on the removal rate and efficiency were investigated. An overall initial removal rate (OIRR) law and a pseudo first-order kinetic (PFOK) model were also developed. The internal diffusion of DMP within the resin phase of D201-OH is the rate-controlling step. Optimization of the particle size and pore structure of the resin D201-OH, the DMP concentration, and the reaction temperature can improve the DMP removal rate. The hydrolysis reaction of DMP catalyzed by D201-OH indicates an overall reaction order of 1.76, a value that is between the first order and the second order. The apparent activation energy of the reaction is 34.6 kJ/mol, which is below the homogeneous alkaline hydrolysis activation energy of 44.3 kJ/mol. The OIRR law can quantify the initial removal rate under different conditions. The results also show that the theoretical DMP removal efficiency predicted by the PFOK model agrees well with the experimentally determined values. Our research provides valuable insights into the primary parameters influencing the kinetic process, which enables a focused improvement in the removal or hydrolysis rate for similar processes.

Anion exchange HPLC isolation of high-density lipoprotein (HDL) and on-line estimation of proinflammatory HDL

Proinflammatory high-density lipoprotein (p-HDL) is a biomarker of cardiovascular disease. Sickle cell disease (SCD) is characterized by chronic states of oxidative stress that many consider to play a role in forming p-HDL. To measure p-HDL, apolipoprotein (apo) B containing lipoproteins are precipitated. Supernatant HDL is incubated with an oxidant/LDL or an oxidant alone and rates of HDL oxidation monitored with dichlorofluorescein (DCFH). Although apoB precipitation is convenient for isolating HDL, the resulting supernatant matrix likely influences HDL oxidation. To determine effects of supernatants on p-HDL measurements we purified HDL from plasma from SCD subjects by anion exchange (AE) chromatography, determined its rate of oxidation relative to supernatant HDL. SCD decreased total cholesterol but not triglycerides or HDL and increased cell-free (cf) hemoglobin (Hb) and xanthine oxidase (XO). HDL isolated by AE-HPLC had lower p-HDL levels than HDL in supernatants after apoB precipitation. XO+xanthine (X) and cf Hb accelerated purified HDL oxidation. Although the plate and AE-HPLC assays both showed p-HDL directly correlated with cf-Hb in SCD plasma, the plate assay yielded p-HDL data that was influenced more by cf-Hb than AE-HPLC generated p-HDL data. The AE-HPLC p-HDL assay reduces the influence of the supernatants and shows that SCD increases p-HDL.

Antimony(V) removal from water by hydrated ferric oxides supported by calcite sand and polymeric anion exchanger

We fabricated and characterized two hybrid adsorbents originated from hydrated ferric oxides (HFOs) using a polymeric anion exchanger D201 and calcite as host. The resultant adsorbents (denoted as HFO-201 and IOCCS) were employed for Sb(V) removal from water. Increasing solution pH from 3 to 9 apparently weakened Sb(V) removal by both composites, while increasing temperature from 293 to 313 K only improved Sb(V) uptake by IOCCS. HFO-201 exhibited much higher capacity for Sb(V) than for IOCCS in the absence of other anions in solution. Increasing ionic strength from 0.01 to 0.1 mol/L NaNO3 would result in a significant drop of the capacity of HFO-201 in the studied pH ranges; however, negligible effect was observed for IOCCS under similar conditions. Similarly, the competing chloride and sulfate pose more negative effect on Sb(V) adsorption by HFO-201 than by IOCCS, and the presence of silicate greatly decreased their adsorption simultaneously, while calcium ions were found to promote the adsorption of both adsorbents. XPS analysis further demonstrated that preferable Sb(V) adsorption by both hybrids was attributed to the inner sphere complexation of Sb(V) and HFO, and Ca(II) induced adsorption enhancement possibly resulted from the formation of HFO-Ca-Sb complexes. Column adsorption runs proved that Sb(V) in the synthetic water could be effectively removed from 30 microg/L to below 5 microg/L (the drinking water standard regulated by China), and the effective treatable volume of IOCCS was around 6 times as that of HFO-201, implying that HFO coatings onto calcite might be a more effective approach than immobilization inside D201.

Bioregeneration of spent anion exchange resin for treatment of nitrate in water

Anion exchange resin treatment is a commonly used technique for removal of nitrate from water. However, spent anion exchange resins are themselves regenerated using brine solution, which produces spent solution containing a high concentration of nitrate and salt. The present study developed a bioregeneration technique for conversion of nitrate on the spent resins to nitrogen gas while eliminating the use of brine solutions. Batch experiments were conducted to investigate the effect of biomass content, pH, salinity, and molar ratio of exogenous organic carbon to nitrate on the kinetics of bioregeneration. The bioregeneration rate decreased when pH increased from 7 to 10. It increased with increasing microbial concentration from 8.3 to 13.8 g/L as volatile suspended solid (VSS) and with decreasing conductivity of the regeneration suspension from 31 to 9 mS/cm. Spent exchange resins were effectively regenerated within 5 h under the optimal conditions and the regenerated resins could be used repeatedly for filtration removal of nitrate from water. A desorption-denitrification model was developed to describe bioregeneration kinetics. Modeling results indicated that the bioregeneration was through desorption of nitrate from the spent resin and subsequent denitrification of the soluble nitrate. Denitrification was the rate-limiting process. This research demonstrated the feasibility of using a biological process to regenerate nitrate-saturated resins.

Determination of arsenate in water by anion selective membrane electrode using polyurethane-silica gel fibrous anion exchanger composite

Polyurethane (PU)-silica (Si gel) based fibrous anion exchanger composites were prepared by solid-gel polymerization of polyurethane in the presence of different amounts of silica gel. The formation of PU-Si gel fibrous anion exchanger composite was characterized by Fourier transform infra-red spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA-DTA), scanning electron microscopy (SEM) and elemental analysis. The membrane having a composition of 5:3 (PU:Si gel) shows best results for water content, porosity, thickness and swelling. Our studies show that the present ion selective membrane electrode is selective for arsenic, having detection limit (1×10(-8)M to 1×10(-1)M), response time (45s) and working pH range (5-8). The selectivity coefficient values for interfering ions indicate good selectivity for arsenate (AsO4(3-)) over interfering anions. The accuracy of the detection limit results was compared by PCA-Arsenomat.

Comparative study on adsorption of perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) by different adsorbents in water

Perfluorinated compounds (PFCs) are emerging environmental pollutants. Perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) are the two primary PFC contaminants that are widely found in water, particularly in groundwater. This study compared the adsorption behaviors of PFOS and PFOA on several commercially available adsorbents in water. The tested adsorbents include granular activated carbon (GAC: Filtrasorb 400), powdered activated carbon, multi-walled carbon nanotube (MCN), double-walled carbon nanotube, anion-exchange resin (AER: IRA67), non-ion-exchange polymer, alumina, and silica. The study demonstrated that adsorption is an effective technique for the removal of PFOS/PFOA from aqueous solutions. The kinetic tests showed that the adsorption onto AER reaches equilibrium rapidly (2 h), while it takes approximately 4 and 24 h to reach equilibrium for MCN and GAC, respectively. In terms of adsorption capacity, AER and GAC were identified as the most effective adsorbents to remove PFOS/PFOA from water. Furthermore, MCN, AER, and GAC proved to have high PFOS/PFOA removal efficiencies (≥98%). AER (IRA67) and GAC (Filtrasorb 400) were thus identified as the most promising adsorbents for treating PFOS/PFOA-contaminated groundwater at mg L(-1) level based on their equilibrium times, adsorption capacities, removal efficiencies, and associated costs.

Biochemical and functional characterization of charge-defined subfractions of high-density lipoprotein from normal adults

High-density lipoprotein (HDL) is regarded as atheroprotective because it provides antioxidant and anti-inflammatory benefits and plays an important role in reverse cholesterol transport. In this paper, we outline a novel methodology for studying the heterogeneity of HDL. Using anion-exchange chromatography, we separated HDL from 6 healthy individuals into five subfractions (H1 through H5) with increasing charge and evaluated the composition and biologic activities of each subfraction. Sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis showed that apolipoprotein (apo) AI and apoAII were present in all 5 subfractions; apoCI was present only in H1, and apoCIII and apoE were most abundantly present in H4 and H5. HDL-associated antioxidant enzymes such as lecithin-cholesterol acyltransferase, lipoprotein-associated phospholipase A2, and paraoxonase 1 were most abundant in H4 and H5. Lipoprotein isoforms were analyzed in each subfraction by using matrix-assisted laser desorption-time-of-flight mass spectrometry. To quantify other proteins in the HDL subfractions, we used the isobaric tags for the relative and absolute quantitation approach followed by nanoflow liquid chromatography-tandem mass spectrometry analysis. Most antioxidant proteins detected were found in H4 and H5. The ability of each subfraction to induce cholesterol efflux from macrophages increased with increasing HDL electronegativity, with the exception of H5, which promoted the least efflux activity. In conclusion, anion-exchange chromatography is an attractive method for separating HDL into subfractions with distinct lipoprotein compositions and biologic activities. By comparing the properties of these subfractions, it may be possible to uncover HDL-specific proteins that play a role in disease.

Stable and selective scintillating anion-exchange sensors for quantification of 99TcO4- in natural freshwaters

New dual functionality scintillating anion-exchange resins were developed for selective determination of (99)TcO4(-) in various natural freshwater samples. Stable scintillating particles were formed by preparing the vinyl monomer 2-[4-(4'-vinylbiphenylyl)]-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (vPBD), starting with the commercial organic flour TBut-PBD and its subsequent copolymerization with styrene, divinylbenzene, and p-chloromethylstyrene mixture. To integrate the radiochemical separation and radiometric detection steps within the same bead, the chloromethyl groups of the scintillating resins were subjected to amination reactions with dioctylamine (DOA) and trioctylamine (TOA). On-line quantification of (99)TcO4(-) was achieved by packing the scintillating anion-exchange resin into Teflon tubing for quantification by a flow scintillation analyzer (FSA). The two functionalized resins were selective for pertechnetate over the common anions in natural freshwaters, especially Cl(-) and SO4(2-) with up to 1000 ppm and with up to 10 ppm I(-) and Cr2O7(2-). The uptake efficiency of the TOA sensor decreased from 97.88% to 85.08% in well water and river water, respectively, while the counting efficiency was almost constant (69.50%). The DOA performance showed lower efficiency in the two water types relative to TOA. On the other hand, the DOA sensor could be regenerated by 5 M HNO3 for reuse at least four times without losing its chemical or optical performance. The detection limit was 1.45 Bq which could be achieved by loading 45 mL from well and tap water containing the maximum contaminant level (MCL) of (99)Tc (33 Bq/L).

Preparation of novel alginate based anion exchanger from Ulva japonica and its application for the removal of trace concentrations of fluoride from water

A green seaweed, Ulva japonica, was modified by loading multivalent metal ions such as Zr(IV) and La(III) after CaCl2 cross-linking to produce metal loaded cross-linked seaweed (M-CSW) adsorbents, which were characterized by elemental analysis, functional groups identification, and metal content determination. Maximum sorption potential for fluoride was drastically increased after La(III) and Zr(IV) loading, which were evaluated as 0.58 and 0.95 mmol/g, respectively. Loaded fluoride was quantitatively desorbed by using dilute alkaline solution for its regeneration. Mechanism of fluoride adsorption was inferred in terms of ligand exchange reaction between hydroxyl ion on co-ordination sphere of the loaded metal ions of M-CSW and fluoride ion in aqueous solution. Application of M-CSW for the treatment of actual waste plating solution exhibited successful removal of fluoride to clear the effluent and environmental standards in Japan, suggesting high possibility of its application for the treatment of fluoride rich waste water.

Diclofenac removal in urine using strong-base anion exchange polymer resins

One of the major sources of pharmaceuticals in the environment is wastewater effluent of which human urine contributes the majority of pharmaceuticals. Urine source separation has the potential to isolate pharmaceuticals at a higher concentration for efficient removal as well as produce a nutrient byproduct. This research investigated the efficacy of using strong-base anion exchange polymer resins to remove the widely detected and abundant pharmaceutical, diclofenac, from synthetic human urine under fresh and ureolyzed conditions. The majority of experiments were conducted using a strong-base, macroporous, polystyrene resin (Purolite A520E). Ion-exchange followed a two-step removal rate with rapid removal in 1 h and equilibrium removal in 24 h. Diclofenac removal was >90% at a resin dose of 8 mL/L in both fresh and ureolyzed urine. Sorption of diclofenac onto A520E resin was concurrent with desorption of an equivalent amount of chloride, which indicates the ion-exchange mechanism is occurring. The presence of competing ions such as phosphate and citrate did not significantly impact diclofenac removal. Comparisons of three polystyrene resins (A520E, Dowex 22, Dowex Marathon 11) as well as one polyacrylic resin (IRA958) were conducted to determine the major interactions between anion exchange resin and diclofenac. The results showed that polystyrene resins provide the highest level of diclofenac removal due to electrostatic interactions between quaternary ammonium functional groups of resin and carboxylic acid of diclofenac and non-electrostatic interactions between resin matrix and benzene rings of diclofenac. Diclofenac was effectively desorbed from A520E resin using a regeneration solution that contained 4.5% (m/m) NaCl in an equal-volume mixture of methanol and water. The greater regeneration efficiency of the NaCl/methanol-water mixture over the aqueous NaCl solution supports the importance of non-electrostatic interactions between resin matrix and benzene rings of diclofenac. Experiments with ketoprofen, in addition to diclofenac, suggest that polystyrene anion exchange resins can be used to selectively remove other acidic pharmaceuticals from urine.

Enhanced adsorption and antifouling performance of anion-exchange resin by the effect of incorporated Fe3O4 for removing humic acid

The application of anion-exchange resins (AERs) is limited by fouling, which increases the fresh resin dosage, regeneration frequency, and amount of regeneration effluent. In this study, five AERs with different Fe3O4 amounts was prepared by increasing the amount of Fe3O4 added to 100 g of monomer mixture for suspension polymerization from 0 g to 40 g. Results showed considerably improved pore volume and hydrophilicity of the resin with increased Fe3O4 content, leading to significantly enhanced adsorption and desorption of humic acid. A method of developing novel resins with enhanced adsorption and antifouling abilities by incorporating Fe3O4 was then proposed. The adsorbent structure resulting from the incorporated inorganic particles was found to be important in determining the adsorption behavior of a hybrid adsorbent.

Characterization of cross-linked cellulosic ion-exchange adsorbents: 1. Structural properties

The structural characteristics of the HyperCel family of cellulosic ion-exchange materials (Pall Corporation) were assessed using methods to gauge the pore dimensions and the effect of ionic strength on intraparticle architecture. Inverse size exclusion chromatography (ISEC) was applied to the S and STAR AX HyperCel derivatives. The theoretical analysis yielded an average pore radius for each material of about 5nm, with a particularly narrow pore-size distribution. Electron microscopy techniques were used to visualize the particle structure and relate it to macroscopic experimental data. Microscopy of Q and STAR AX HyperCel anion exchangers presented some qualitative differences in pore structure that can be attributed to the derivatization using conventional quaternary ammonium and salt-tolerant ligands, respectively. Finally, the effect of ionic strength was studied through the use of salt breakthrough experiments to determine to what extent Donnan exclusion plays a role in restricting the accessible pore volume for small ions. It was determined that Donnan effects were prevalent at total ionic strengths (TIS) less than 150mM, suggesting the presence of a ligand-containing partitioning volume within the pore space.

Enhanced removal of fluoride by polystyrene anion exchanger supported hydrous zirconium oxide nanoparticles

Here we fabricated a novel nanocomposite HZO-201, an encapsulated nanosized hydrous zirconium oxide (HZO) within a commercial porous polystyrene anion exchanger D201, for highly efficient defluoridation of water. HZO-201 exhibited much higher preference than activated alumina and D201 toward fluoride removal when competing anions (chloride, sulfate, nitrate, and bicarbonate) coexisted at relatively high levels. Fixed column adsorption indicated that the effective treatable volume of water with HZO-201 was about 7-14 times as much as with D201 irrespective of whether synthetic solution or groundwater was the feeding solution. In addition, HZO-201 could treat >3000 BV of the acidic effluent (around 3.5 mg F(-)/L) per run at pH 3.5, compared to only ∼4 BV with D201. The exhausted HZO-201 could be regenerated by NaOH solution for repeated use without any significant capacity loss. Such attractive performance of HZO-201 resulted from its specific hybrid structure, that is, the host anion exchanger D201 favors the preconcentration of fluoride ions inside the polymer based on the Donnan principle, and the encapsulated nanosized HZO exhibits preferable sequestration of fluoride through specific interaction, as further demonstrated by XPS spectra. The influence of solution pH, competitive anions, and contact time was also examined. The results suggested that HZO-201 has a great potential in efficient defluoridation of groundwater and acidic mine drainage.

Evaluating chemical extraction techniques for the determination of uranium oxidation state in reduced aquifer sediments

Extraction techniques utilizing high pH and (bi)carbonate concentrations were evaluated for their efficacy in determining the oxidation state of uranium (U) in reduced sediments collected from Rifle, CO. Differences in dissolved concentrations between oxic and anoxic extractions have been proposed as a means to quantify the U(VI) and U(IV) content of sediments. An additional step was added to anoxic extractions using a strong anion exchange resin to separate dissolved U(IV) and U(VI). X-ray spectroscopy showed that U(IV) in the sediments was present as polymerized precipitates similar to uraninite and/or less ordered U(IV), referred to as non-uraninite U(IV) species associated with biomass (NUSAB). Extractions of sediment containing both uraninite and NUSAB displayed higher dissolved uranium concentrations under oxic than anoxic conditions while extractions of sediment dominated by NUSAB resulted in identical dissolved U concentrations. Dissolved U(IV) was rapidly oxidized under anoxic conditions in all experiments. Uraninite reacted minimally under anoxic conditions but thermodynamic calculations show that its propensity to oxidize is sensitive to solution chemistry and sediment mineralogy. A universal method for quantification of U(IV) and U(VI) in sediments has not yet been developed but the chemical extractions, when combined with solid-phase characterization, have a narrow range of applicability for sediments without U(VI).

Assessing gibberellins oxidase activity by anion exchange/hydrophobic polymer monolithic capillary liquid chromatography-mass spectrometry

Bioactive gibberellins (GAs) play a key regulatory role in plant growth and development. In the biosynthesis of GAs, GA3-oxidase catalyzes the final step to produce bioactive GAs. Thus, the evaluation of GA3-oxidase activity is critical for elucidating the regulation mechanism of plant growth controlled by GAs. However, assessing catalytic activity of endogenous GA3-oxidase remains challenging. In the current study, we developed a capillary liquid chromatography--mass spectrometry (cLC-MS) method for the sensitive assay of in-vitro recombinant or endogenous GA3-oxidase by analyzing the catalytic substrates and products of GA3-oxidase (GA1, GA4, GA9, GA20). An anion exchange/hydrophobic poly([2-(methacryloyloxy)ethyl]trimethylammonium-co-divinylbenzene-co-ethylene glycol dimethacrylate)(META-co-DVB-co-EDMA) monolithic column was successfully prepared for the separation of all target GAs. The limits of detection (LODs, Signal/Noise = 3) of GAs were in the range of 0.62-0.90 fmol. We determined the kinetic parameters (K m) of recombinant GA3-oxidase in Escherichia coli (E. coli) cell lysates, which is consistent with previous reports. Furthermore, by using isotope labeled substrates, we successfully evaluated the activity of endogenous GA3-oxidase that converts GA9 to GA4 in four types of plant samples, which is, to the best of our knowledge, the first report for the quantification of the activity of endogenous GA3-oxidase in plant. Taken together, the method developed here provides a good solution for the evaluation of endogenous GA3-oxidase activity in plant, which may promote the in-depth study of the growth regulation mechanism governed by GAs in plant physiology.

Anion exchange resins as a source of nitrosamines and nitrosamine precursors

Anion exchange resins are important tools for the removal of harmful anionic contaminants from drinking water, but their use has been linked to the presence of carcinogenic nitrosamines in treated drinking water. In bench-scale batch and column experiments, anion exchange resins from a large, representative group were investigated as sources of the nitrosamines N-nitrosodimethylamine (NDMA), N-nitrosodiethylamine (NDEA), N-nitrosodi-n-propylamine (NDPA), and N-nitrosodi-n-butylamine (NDBA) and their precursors. Several resins were found to release high levels (up to >2000 ng/L, orders of magnitude above drinking water regulatory levels) of nitrosamines upon initial rinsing with lab-grade water, with levels subsiding within 50-100 bed volumes of rinsing. Resins released similarly high levels of nitrosamine precursors, with spikes in precursor release triggered by regeneration of resins with sodium chloride or by interruptions in flow resulting in prolonged contact times. Free chlorine or preformed monochloramine in feedwater led to the production of nitrosamines. Resins released different nitrosamines and precursors depending on their functional groups, with some resins releasing as many as three different nitrosamines and their precursors. These findings have significant implications for the pretreatment and appropriate use of anion exchange resins by drinking water utilities and for the production of anion exchange resins by manufacturers.

Dissolution of synthetic uranium dibutyl phosphate deposits in oxidizing and reducing chemical formulations

Permanganate and nitrilotriacetic acid (NTA) based dilute chemical formulations were evaluated for the dissolution of uranium dibutyl phosphate (U-DBP), a compound that deposits over the surfaces of nuclear reprocessing plants and waste storage tanks. A combination of an acidic, oxidizing treatment (nitric acid with permanganate) followed by reducing treatment (NTA based formulation) efficiently dissolved the U-DBP deposits. The dissolution isotherm of U-DBP in its as precipitated form followed a logarithmic fit. The same chemical treatment was also effective in dissolving U-DBP coated on the surface of 304-stainless steel, while resulting in minimal corrosion of the stainless steel substrate material. Investigation of uranium recovery from the resulting decontamination solutions by ion exchange with a bed of mixed anion and cation resins showed quantitative removal of uranium.

Determination of thallium at ultra-trace levels in water and biological samples using solid phase spectrophotometry

A new simple, very sensitive, selective and accurate procedure for the determination of trace amounts of thallium(III) by solid-phase spectrophotometry (SPS) has been developed. The procedure is based on fixation of Tl(III) as quinalizarin ion associate on a styrene-divinylbenzene anion-exchange resin. The absorbance of resin sorbed Tl(III) ion associate is measured directly at 636 and 830 nm. Thallium(I) was determined by difference measurements after oxidation of Tl(I) to Tl(III) with bromine. Calibration is linear over the range 0.5-12.0 μg L(-1) of Tl(III) with relative standard deviation (RSD) of 1.40% (n=10). The detection and quantification limits are 150 and 495 ng L(-1) using 0.6 g of the exchanger. The molar absorptivity and Sandell sensitivity are also calculated and found to be 1.31×10(7) L mol(-1)cm(-1) and 0.00156 ng cm(-2), respectively. The proposed procedure has been successfully applied to determine thallium in water, urine and serum samples.

Sorption of Pb(II) onto a mixture of algae waste biomass and anion exchanger resin in a packed-bed column

Sorption of Pb(II) was studied by using a biosorbent mixture of algae waste biomass and Purolite A-100 resin in a packed-bed column. Mixing these two components was done to prevent the clogging of the column and to ensure adequate flow rates. Increasing of solution flow rate and initial Pb(II) concentration make that the breakthrough and saturation points to be attained earlier. The experimental breakthrough curves were modeled using Bohart-Adams, Thomas and Yoon-Nelson models, and the parameters for all these models were calculated. A regeneration efficiency of 98% was achieved using 0.1 mol L(-1) HCl and not significant changes in lead uptake capacity after three biosorption/desorption cycles were noted. The biosorbent mixture was able to remove Pb(II) from synthetic wastewater at pH 5.0 and flow rate of 3.5 mL min(-1), and the obtained effluent has better quality characteristics. The biosorbent mixture it is suitable for a continuous system for large-scale applications.

Removal of chromium (VI) from electroplating wastewater using an anion exchanger derived from rice straw

An anion exchanger from rice straw was used to remove Cr (VI) from synthetic wastewater and electroplating effluent. The exchanger was characterized using Fourier transform infrared (FTIR) spectrum and scanning electron microscopy (SEM), and it was found that the quaternary amino group and hydroxyl group are the main functional groups on the fibrous surface of the exchanger. The effect of contact time, initial concentration and pH on the removal of Cr (VI), and adsorption isotherms at different temperature, was investigated. The results showed that the removal of Cr (VI) was very rapid and was significantly affected by the initial pH of the solution. Although acidic conditions (pH = 2-6) facilitated Cr (VI) adsorption, the exchanger was effective in neutral solution and even under weak base conditions. The equilibrium data fitted well with Langmuir adsorption model, and the maximum Cr (VI) adsorption capacities at pH 6.4 were 0.35, 0.36 and 0.38 mmol/g for 15, 25 and 35 degrees C, respectively. The exchanger was finally tested with real electroplating wastewater, and at sorbent dosage of 10 g/L, the removal efficiencies for Cr (VI) and total Cr were 99.4% and 97.8%, respectively. In addition, the positive relationship between adsorbed Cr (VI) and desorbed Cl- suggested that Cr (VI) was mainly removed by ion exchange with chlorine.

Selective removal of nitrate ion using a novel composite carbon electrode in capacitive deionization

We fabricated nitrate-selective composite carbon electrodes (NSCCEs) for use in capacitive deionization to remove nitrate ions selectively from a solution containing a mixture of anions. The NSCCE was fabricated by coating the surface of a carbon electrode with the anion exchange resin, BHP55, after grinding the resin into fine powder. BHP55 is known to be selective for nitrate ions. We performed desalination experiments on a solution containing 5.0 mM NaCl and 2.0 mM NaNO(3) using the NSCCE system constructed with the fabricated electrode. The selective removal of nitrate in the NSCCE system was compared to a membrane capacitive deionization (MCDI) system constructed with ion exchange membranes and carbon electrodes. The total quantity of chloride and nitrate ions adsorbed onto the unit area of the electrode in the MCDI system was 25 mmol/m(2) at a cell potential of 1.0 V. The adsorption of nitrate ions was 8.3 mmol/m(2), accounting for 33% of the total. In contrast, the total anion adsorption in the NSCCE system was 34 mmol/m(2), 36% greater than the total anion adsorption of the MCDI system. The adsorption of nitrate ions was 19 mmol/m(2), 2.3-times greater than the adsorption in the MCDI system. These results showed that the ions were initially adsorbed by an electrostatic force, and the ion exchange reactions then occurred between the resin powder in the coated layer and the solution containing mixed anions.

Identification of effluent organic matter fractions responsible for low-pressure membrane fouling

Anion exchange resin (AER), powder activated carbon (PAC) adsorption and ozonation treatments were applied on biologically treated wastewater effluent with the objective to modify the effluent organic matter (EfOM) matrix. Both AER and PAC led to significant total organic carbon (TOC) removal, while the TOC remained nearly constant after ozonation. Liquid Chromatography-Organic Carbon Detection (LC-OCD) analysis showed that the AER treatment preferentially removed high and intermediate molecular weight (MW) humic-like structures while PAC removed low MW compounds. Only a small reduction of the high MW colloids (i.e. biopolymers) was observed for AER and PAC treatments. Ozonation induced a large reduction of the biopolymers and an important increase of the low MW humic substances (i.e. building blocks). Single-cycle microfiltration (MF) and ultrafiltration (UF) tests were conducted using commercially available hollow fibres at a constant flux. After reconcentration to their original organic carbon content, the EfOM matrix modified by AER and PAC treatments exhibited higher UF membrane fouling compared to untreated effluent; result that correlated with the higher concentration of biopolymers. On the contrary, ozonation which induced a significant degradation of the biopolymers led to a minor flux reduction for both UF and MF filtration tests. Based on a single filtration, results indicate that biopolymers play a major role in low pressure membrane fouling and that intermediate and low MW compounds have minor impact. Thus, this approach has shown to be a valid methodology to identify the foulant fractions of EfOM.

Branched polymeric media: perchlorate-selective resins from hyperbranched polyethyleneimine

Perchlorate (ClO(4)(-)) is a persistent contaminant found in drinking groundwater sources in the United States. Ion exchange (IX) with selective and disposable resins based on cross-linked styrene divinylbenzene (STY-DVB) beads is currently the most commonly utilized process for removing low concentrations of ClO(4)(-) (10-100 ppb) from contaminated drinking water sources. However, due to the low exchange capacity of perchlorate-selective STY-DVB resins (∼0.5-0.8 eq/L), the overall cost becomes prohibitive when treating groundwater with higher concentration of ClO(4)(-) (e.g., 100-1000 ppb). In this article, we describe a new perchlorate-selective resin with high exchange capacity. This new resin was prepared by alkylation of branched polyethyleneimine (PEI) beads obtained from an inverse suspension polymerization process. Batch and column studies show that our new PEI resin with mixed hexyl/ethyl quaternary ammonium chloride exchange sites can selectively extract trace amounts of ClO(4)(-) from a makeup groundwater (to below detection limit) in the presence of competing ions. In addition, this resin has a strong-base exchange capacity of 1.4 eq/L, which is 1.75-2.33 times larger than those of commercial perchlorate-selective STY-DVB resins. The overall results of our studies suggest that branched PEI beads provide versatile and promising building blocks for the preparation of perchlorate-selective resins with high exchange capacity.

A fabrication strategy for nanosized zero valent iron (nZVI)-polymeric anion exchanger composites with tunable structure for nitrate reduction

To reveal how the distribution of nanoscale zero-valent iron (nZVI) affect their reduction efficiency of its polymer-based composites and to further develop a simple strategy to tune the structure of the composites, we prepared four nZVI-polymerstyrene anion exchanger composites with similar nZVI loadings (13.5-14.4 Fe % in mass) but different distributions just through varying the concentration of NaBH(4) (0.9, 1.8, 3.6, and 7.2% in mass) solution during reduction of nZVI precursor (FeCl(4)(-) anions). As observed by SEM-EDX images, increasing the NaBH(4) concentration resulted in a more uniform nZVI distribution within the polymer, and thereto higher NH(4)(+)N production, faster reaction rate and more gaseous products during its reduction of nitrate and nitrite. nZVI distribution of the composites was suggested to greatly depend upon two processes, the hydrolyzation of anionic FeCl(4)(-) into cationic Fe(3+) and the reduction of both Fe(III) species by NaBH(4). Higher NaBH(4) concentration favored its faster diffusion into the inside polymer and in situ reduction of Fe(III) species into nZVI, causing a more uniform nZVI distribution. The results reported herein suggest that adjusting the NaBH(4) concentration was a simple and effective method to control the nZVI distribution in the supporting polymers, and indirectly tune the reactivity of the resultant nZVI hybrids.

Comparison of sample preparation methods for stable isotope analysis of dissolved sulphate in forested watersheds

Pretreatment methods for measuring stable sulphur (δ(34)S) and oxygen (δ(18)O) isotope ratios of dissolved sulphate from watersheds have evolved throughout the last few decades. The current study evaluated if there are differences in the measured stable S and O isotope values of dissolved sulphate from forested watersheds when pretreated using three different methods: Method 1 (M1): adsorb sulphate on anion exchange resins and send directly to isotope facility; Method 2 (M2): adsorb sulphate on anion exchange resins, extract sulphate from anion exchange resins, and send the produced BaSO(4) to the isotope facility; and Method 3 (M3): directly precipitate BaSO(4) without anion exchange resins with the precipitates being sent to the isotope facility. We found an excellent agreement of the δ(34)S(sulphate) values among all the three methods. However, some differences were observed in the δ(18)O(sulphate) values (M1 versus M2:-1.5 ‰; M1 versus M3:-1.2 ‰) associated with possible O contamination before isotope measurement. Several approaches are recommended to improve the pretreatment procedures for δ(18)O(sulphate) analysis.

Development and calibration of a passive sampler for perfluorinated alkyl carboxylates and sulfonates in water

Perfluorinated chemicals (PFCs) are emerging environmental contaminants with a global distribution. Due to their moderate water solubility, the majority of the environmental burden is assumed to be in the water phase. This work describes the application of the first passive sampler for the quantitative assessment of concentrations of perfluorinated alkylcarboxylates (PFCAs) and sulfonates (PFSAs) in water. The sampler is based on a modified Polar Organic Chemical Integrative Sampler (POCIS) with a weak anion exchange sorbent as a receiving phase. Sampling rates were between 0.16 and 0.37 L d(-1), and the duration of the kinetic sampling stage was between 2.2 and 13 d. A field deployment in the most urbanized estuary in Australia (Sydney Harbour) showed trace level concentrations from passive samplers (0.1-12 ng L(-1)), in good agreement with parallel grab sampling (0.2-16 ng L(-1)). A separate field comparison of the modified POCIS with standard POCIS suggests the latter may have application for PFC sampling, but with a more limited range of analytes than the modified POCIS which contains a sorbent with a mixed mode of action.

Resin-derived hierarchical porous carbon spheres with high catalytic performance in the oxidative dehydrogenation of ethylbenzene

Pre-shaped hierarchical porous carbon (HPC) spheres have been synthesized through a facile anion exchanged route. An industrial polymeric anion-exchange resin with a hierarchical pore structure was used as the carbon precursor. Its high porosity was conserved using an aluminate/silicate precursor forming a hard support to prevent the structural collapse during the carbonization process. Physicochemical bulk and surface properties of the obtained HPC spheres were characterized by X-ray diffraction, scanning and transmission electron microscopy, N(2) physisorption, and X-ray photoemission spectroscopy. Results obtained indicate that HPC keeps the abundant hierarchical porosity including meso- and macropores as well as the high surface area of the resin precursor. The as-synthesized HPC spheres were tested as a catalyst for oxidative dehydrogenation of ethylbenzene to styrene. The oxygen-rich catalyst surface formed under reaction conditions shows a high catalytic performance and stability, making HPC to a potential catalyst for this type of reaction.

A polishing hybrid AER/UF membrane process for the treatment of a high DOC content surface water

The efficacy of a combined AER/UF (Anion Exchange Resin/Ultrafiltration) process for the polishing treatment of a high DOC (Dissolved Organic Carbon) content (>8 mgC/L) surface water was investigated at lab-scale using a strong base AER. Both resin dose and bead size had a significant impact on the kinetic removal of DOC for short contact times (i.e. <15 min). For resin doses higher than 700 mg/L and median bead sizes below 250 μm DOC removal remained constant after 30 min of contact time with very high removal rates (80%). Optimum AER treatment conditions were applied in combination with UF membrane filtration on water previously treated by coagulation-flocculation (i.e. 3 mgC/L). A more severe fouling was observed for each filtration run in the presence of AER. This fouling was shown to be mainly reversible and caused by the progressive attrition of the AER through the centrifugal pump leading to the production of resin particles below 50 μm in diameter. More important, the presence of AER significantly lowered the irreversible fouling (loss of permeability recorded after backwash) and reduced the DOC content of the clarified water to l.8 mgC/L (40% removal rate), concentration that remained almost constant throughout the experiment.

Multi-cycle bioregeneration of spent perchlorate-containing macroporous selective anion-exchange resin

Ion exchange using perchlorate-selective resin is possibly the most feasible technology for perchlorate removal from water. However, in current water treatment applications, selective resins are used once and then incinerated, making the ion-exchange process economically and environmentally unsustainable. A new concept has been developed involving the biological regeneration of resin-containing perchlorate. This concept involves directly contacting perchlorate-containing resins with a perchlorate-reducing microbial culture. In this research, the feasibility of multi-cycle loading and bioregeneration of a macroporous perchlorate-selective resin was investigated. Loading and bioregeneration cycles were performed, using a bench-scale fermenter and a fluidized bed reactor followed by fouling removal and disinfection of the resin. The results revealed that selective macroporous resin can be employed successfully in a consecutive loading-bioregeneration ion-exchange process. Loss of resin capacity stabilized after a few cycles of bioregeneration, indicating that the number of loading and bioregeneration cycles that can be performed is likely greater than the five cycles tested. The results also revealed that most of the capacity loss in the resin is due to perchlorate buildup from previous regeneration cycles. The results further indicated that as the bioregeneration progresses, clogging of the resin pores results in strong mass transfer limitation in the bioregeneration process.

High-throughput multimodal strong anion exchange purification and N-glycan characterization of endogenous glycoprotein expressed in glycoengineered Pichia pastoris

The secretory pathway of the yeast Pichia pastoris has been engineered to produce complex human-type N-glycans (Choi et al., Proc Natl Acad Sci USA 100:5022-5027, 2003; Hamilton et al., Science 301:1244-1246, 2003; Hamilton et al., Science 313:1441-1443, 2006). In contrast to the heterogeneous glycans produced on the therapeutic glycoproteins expressed in mammalian cell lines, glycoengineered P. pastoris can be designed to produce a specific, preselected glycoform. In order to achieve glycan uniformity on the target protein, No Open Reading Frame (NORF) yeast cell lines are screened extensively during various stages of glycoengineering. In the absence of the target protein of interest, screening the NORF yeast cell lines for glycoform uniformity becomes a challenge. The common approach so far has been to analyze the total cell glycan pool released from glycoproteins of the NORF yeast cells to predict the N-glycan uniformity. As this does not always accurately predict the N-glycan end product, we describe in this chapter a detailed protocol for a non-affinity-based high-throughput purification of an endogenous glycoprotein. This protein of interest has been introduced during the early stages of glycoengineering process and its N-glycan profile is utilized as a tool for glycoengineering screening.