Organic Ion Exchange Research Articles

ISOLATION OF SUCCINIC ACID FROM FERMENTATION BROTHS BY DIRECT CRYSTALLIZATION

It has been shown that succinic acid can be isolated from culture liquid obtained by growing Escherichia coli at neutral pH or Yarrowia lipolytica yeast at low pH values. The method is based on the direct crystallization of the target product from CL, includes a few simple stages, and does not require organic solvents, membranes or ion-exchangers. Activated carbon and hydrochloric acid are the only consumables needed. The method permits to achieve a high yield (80—90%) and 97% purity of succinic acid.

PVDF supported silica immobilized phosphotungstic acid membrane for DMFC application

Abstract Silica immobilized phosphotungstic acid (Si-PWA) based inorganic–organic hybrid ion exchange membrane was used in direct methanol fuel cell (DMFC). Chemical composition of the ion exchanging phase of membrane was determined using energy dispersive spectroscopy (EDS). TGA analysis showed that the thermal stability of synthesized membrane was better than Nafion-117 and it also possessed excellent water holding capacity even at elevated temperature. The proton conductivity of the membrane increased upon increasing the PWA concentration in silica. Room temperature (25 °C) proton conductivity of the membrane was 4.3 m Scm − 1 and it increased to 10.1 m Scm − 1 upon increasing temperature to 60 °C. At 25 °C and 60% relative humidity, the peak power density of DMFC with synthesized membrane (21.6 m Wcm − 2 ) was much better than that of DMFC with Nafion-117 membrane (11 m Wcm − 2 ).

KNiFe(CN)6전기화학적 이온교환체를 이용한 세슘 양이온의 분리에 관한 연구

본 연구에서는 전기화학적 이온교환체 중의 하나인 nickel hexacyanoferrate(<TEX>$KNiFe(CN)_6$</TEX>) 막 전극을 사용하여 세슘 양이온을 분리하는 실험을 수행하였다. 1.0M <TEX>$NaNO_3$</TEX>와 1.0M <TEX>$CsNO_3$</TEX>의 단일성분계 및 이성분계 수용액에서 순환전위곡선을 측정하여 전극전위, 전류, 전기량의 변화 거동을 조사하였으며, 실험 전과 후에 <TEX>$KNiFe(CN)_6$</TEX> 막의 구조 형태와 원자조성의 변화를 각각 SEM과 EDS 분석을 통하여 조사하였다. 또한 나트륨과 세슘 용액에서 교대로 이온교환 반응을 수행하여 측정한 순환전위곡선과 원자조성으로부터 <TEX>$KNiFe(CN)_6$</TEX>의 이온 선택성을 조사하였다. 본 연구의 실험 결과에 의하면, 전기를 인가한 <TEX>$KNiFe(CN)_6$</TEX> 이온교환체는 화학적 유 무기물 이온교환체에 비해 약 40배 이상의 우수한 내구성을 가짐을 알 수 있었다. 또한 <TEX>$KNiFe(CN)_6$</TEX> 이온교환체는 나트륨보다 세슘에 대해 보다 높은 선택도를 가짐을 확인할 수 있었다. This study was performed to investigate the separation of cesium cations by using an electrochemical ion exchanger of nickel hexacyanoferrate(<TEX>$KNiFe(CN)_6$</TEX>) film electrode. Potential, current, and charge passing through the cyclic voltammograms were measured in singular and binary solutions of 1.0M <TEX>$NaNO_3$</TEX> and 1.0M <TEX>$CsNO_3$</TEX>. Before and after each experiment, the structural morphology and atomic composition of <TEX>$KNiFe(CN)_6$</TEX> were analyzed by SEM and EDS, respectively. The ion selectivity of <TEX>$KNiFe(CN)_6$</TEX> was also observed by the voltammograms and atomic compositions measured in the solution alternated between sodium and cesium. As the result of this study, it was found that the electrically switched <TEX>$KNiFe(CN)_6$</TEX> ion exchanger had the significant advantage of 40 times or longer durability than conventional organic or inorganic ion exchanger. It was also shown that the <TEX>$KNiFe(CN)_6$</TEX> ion exchanger had high selectivity for cesium over sodium.

Cation exchange PVA/SPPO/SiO2 membranes with double organic phases for alkali recovery

Cation exchange hybrid membranes are prepared from sulfonated poly(2,6-dimethyl-1,4-phenylene oxide) (SPPO), polyvinyl alcohol (PVA) and tetraethoxysilane (TEOS). The membranes contain double organic phases of PVA and SPPO, and thus can combine their advantages of organic solvent resistance and ion exchange property. The SPPO phase is encapsuled in PVA/SiO2 matrix, and thus the crosslinking degree of PVA/SiO2 matrix decreases.The hybrid membranes have the ion exchange capacities (IECs) of 0.44–1.34mmol/g, and are stable in ethanol. The ethanol uptake (ER) is in the range of 1.3–21.3%, and the swelling degree in 65°C ethanol is in the range of 7.5–54.5%. The membranes have the tensile strength (TS) of 30–70MPa, with the elongation at break (Eb) of 5–13%. The initial decomposition temperatures are all higher than 220°C. Diffusion dialysis (DD) test indicates that, the membranes can be potentially applied for alkali recovery. The dialysis coefficient of NaOH (UOH) is in the range of 0.007–0.013m/h, and the highest separation factor (S) can reach up to 181. The DD performance may be influenced by three aspects, including membrane hydrophilicity, IEC and the interstices between PVA and SPPO phases. Methods of aldehyde crosslinking and ethanol swelling are compared to enhance membrane stability, and the ethanol swelling is more beneficial to DD process.

Separation of Americium from Curium by Oxidation and Ion Exchange

Nuclear energy has the potential to be a clean alternative to fossil fuels, but in order for it to play a major role in the US, many questions about the back end of the fuel cycle must be addressed. One of these questions is the difficult separation of americium from curium. Here, we report the oxidation of Am in two systems, perchloric acid and nitric acid and the affect of changing the acid has on the oxidation. K(d) values were observed and a direct separation factor was calculated and was seen to be as high as 20 for four metal(IV) pillared phosphate phosphonate inorganic organic hybrid ion exchange materials. These ion exchangers are characterized by very low selectivity for cations with low charge but extremely high uptake of ions of high charge.

Potentiometric sensors based on organic ion exchangers for determining tetraalkylammonium salts

Potentiometric sensors with plasticized polymer membranes based on organic ion exchangers, tetraalkylammonium dodecyl sulfates (benzyldimethyldodecylammonium, benzyldimethyltetradecylammonium, dimethyldistearylammonium), have been proposed for the determination of quaternary ammonium salts in model solutions and KATAPAV technical solutions. The thermal stability, composition, and solubility product have been estimated. It has been shown that ion associates are stable to 60–70°C, KS varies in the range from 2 × 10−8 to 5 × 10−10. The basic electrochemical parameters of the sensors have been determined as well, such as linearity ranges of the electrode function (5 × 10−5 (5 × 10−6)−1 × 10−2 (1 × 10−3) M) and slopes of the electrode functions (47–59 mV/pc), response time (60–90 sec), potential drift (2–3 mV/day), operation period (3–4 months), limits of detection for tetramethylammonium salts (1 × 10−5−4 × 10−7 M).

Effects of Increased Salinity and Inundation on Inorganic Nitrogen Exchange and Phosphorus Sorption by Tidal Freshwater Floodplain Forest Soils, Georgia (USA)

We investigated the effects of increasing salinity and inundation on inorganic N exchange and P sorption/precipitation in soils of tidal freshwater floodplain forests (TFFF) of coastal Georgia, USA. Our objectives were to better understand how sea level rise, increasing inundation, and saltwater intrusion will affect the ability of TFFFs to retain nitrogen (N) and phosphorus (P). We collected soil cores (0–5 cm) from three TFFFs that do not currently experience saltwater intrusion and from one TFFF currently experiencing saltwater intrusion and measured NH4-N exchange and PO4-P removal over five simulated 6-h tidal cycles using nutrient-enriched freshwater (30 μM NH4-N and 5 μM PO4-P). In a second experiment, we exposed soil cores to three salinities (0, 2, and 5) and two inundation depths (5 and 10 cm) using the same nutrient enrichment. When flooded with nutrient-enriched freshwater, soils from the three TFFFs that do not experience saltwater intrusion removed inorganic N and P in amounts ranging from 5.2 to 10.7 and 2.3 to 4.4 mg/m2, respectively, and the TFFF soils experiencing saltwater intrusion removed 2.1 to 3.8 mg P/m2. However, TFFF soils experiencing saltwater intrusion released inorganic N to the water column in amounts ranging from 7.1 to 67.5 mg/m2. In the second experiment, soils from TFFFs not experiencing saltwater intrusion released NH4-N to the water column when exposed to 2 and 5 salinity, and the amount of N released increased with salinity and number of tidal cycles. In contrast, the same TFFF soils sorbed two and three times more PO4-P when exposed to 2 and 5 salinity than when exposed to 0 salinity. P removal on a mass basis was greater under 10 cm of inundation, but the efficiency of removal was greater under the 5 cm flooding depth. Our findings suggest that saltwater intrusion caused by sea level rise will promote N release into the water column through organic matter mineralization and/or ion exchange and may promote P sorption, or precipitation of P with metal cations. In addition, release of N and resulting increased N/P could exacerbate eutrophication of estuaries in the future.

Potentiometric sensors based on organic ion exchangers of tetraalkylammonium and silver complexes with ampicillin, oxacillin, and cefazolin

Potentiometric sensors with plasticized polymer membranes based on tetraalkylammonium organic ion exchangers and silver(I) complexes with ampicillin, oxacillin, and cefazolin are proposed for the quantification of antibiotics in model mixtures. The quantitative parameters of complex species of silver with β-lactam antibiotics (β-lac) are established. The complexes (β-lac)2Ag are shown applicable as electroactive components of membranes of potentiometric sensors with tetraalkylammonium cations as counterions. For the information on potentiometric selectivity coefficients and the parameters of cross-sensitivity of sensors in solutions of β-lactam antibiotics they might be used in multisensor systems of the electronic tongue type. The analytical signals are processed by the method of neural network. The average relative error of the individual quantification of β-lactam antibiotics in three-component model mixtures was 4–6%.

Nuclear Energy: A Perspective on Recent Results on the Removal of Strontium from Waste

Nuclear Energy: A Perspective on Recent Results on the Removal of Strontium from Waste

Influence of antioxidant extraction on fermentability of olive biomass hydrolysates

Olive tree biomass has been proposed as raw material for ethanol production by means of a biochemical process. The pretreatment is one of the key steps which results in a celluloseenriched pretreated solid and a liquid fraction (hydrolysate) containing most of the hemicellulosic derived sugars, as well as degradation products from sugars and lignin and other minor components. It is of great interest the presence in these hydrolysates of compounds with antioxidant capacity, because their exploitation could affect positively the economy of the global process. This work deals with the fermentation of olive tree biomass hydrolysates by Pichia stipitis. Hydrolysates were prepared from biomass submitted to steam explosion and liquid hot water pretreatments, at different temperatures (170–240 ◦ C). Hydrolysates were further submitted to a process aimed at separating compounds with antioxidant capacity and improve fermentation results by eliminating yeast inhibitors. The fermentability of the hydrolysates before and after separation of these compounds is compared. Separation procedures include organic solvent extraction (e.g., ethyl acetate, which separates phenolic compounds) and ion exchange resins, which allow interesting compounds to be obtained, mainly hydroxytirosol. In the latter case, the process described in the patent procedure (US 2004/0102657A1) is followed, including the use of an anionic resin for retaining certain polyphenolic compounds, and then elution with water.

The effect of an organic ion-exchange resin on properties of heterogeneous ion-exchange membrane

This case study deals with relationships between characteristic properties of organic ionexchange resins and heterogeneous ion-exchange membranes. At first chemical and temperature stability, humidity and particle size distribution of different types of ion-exchange resins was analyzed. Subsequently, membranes were prepared by using different filler/polymer matrix ratio or by using milled resins with different particle size distribution. Finally, different ion-exchange resins were used for preparing of heterogeneous ion-exchange membranes at fixed filler/polymer matrix ratio. We analyzed many characteristic properties of raw materials, intermediate and final products and we paid attention to process parameters during preparing of membranes too. It was proved that there are important relationships between properties of a membrane and the type of resin used for its preparation and the process of membrane preparation. The results show that most of ion-exchange resins can be used for ion-exchange membranes preparation but with different impact on characteristic properties of membranes. We also proved that increasing of filler/polymer matrix ratio or using very fine particle size distribution of milled resin improve electrochemical properties of membranes at the expense of worst mechanical properties and more complicated membrane preparation. On the basis of these results we are able to modify composition of heterogeneous ion-exchange membranes to reach required properties.

Effect of gamma radiation on organic ion exchangers

Effects of gamma radiation on indigenous strong cation and anion exchange resins have been studied in HCl medium up to a dosage of 3600 kGy. The ion exchange capacities of cation and anion exchangers decreased by around 20% at 2400 kGy of absorbed dose. Decrease in salt-splitting capacity and total exchange capacity for both cation and anion exchangers were comparable up to 2400 kGy. Above 2400 kGy, a marginal loss in the capacity was observed for cation exchangers whereas a drastic reduction was noticed for the anion exchangers. The distribution coefficients for zirconium, antimony and cobalt, measured in HCl medium, did not change significantly for 2400 kGy of absorbed dose. Crushing strength and moisture retention capacity did not exhibit any specific trend with the absorbed dose.

Radiation-Induced Degradation in Ion Exchange Resins for a Water Detritiation System

The combined electrolysis and catalytic exchange process has been selected for the water detritiation system for the ITER. In the front-end process of tritiated water electrolyzer composed of a solid polymer electrode, ion exchange resin beds are installed for processing effluent ions in the enriched tritiated water from the catalytic exchange column to avoid the deterioration of the solid polymer electrode. The tritium concentration in the circulation resin bed is evaluated to reach 1.09x1015Bq/m3. It is thus important to note the radiation-induced degradation in ion exchange resins. We studied the degradation effects in Amberlite[registered] and Diaion[registered] organic ion exchange resins caused by the irradiation with electron beam up to the integrated dose of 1500kGy. The procedures D2187-94 of the American Society for Testing and Materials were adopted for the evaluation of the water retention capacity, the backwashed and settled density, the salt splitting capacity, and the total exchange capacity of particulate ion exchange resins. A 20% decrease of total exchange capacity of the cation exchange resin, when irradiated up to 1500 kGy at room temperature, has been observed.

Treatability of resin effluents by electrochemical oxidation using batch recirculation reactor

Electro oxidation processes are developed throughout the world for ambient temperature destruction of organic wastes. Several of these processes are based on mediated electrochemical oxidation. This article presents the experimental results of electro chemical study based on mediated electrochemical oxidation process conducted for synthetic organic ion exchange resin materials. Investigation was carried out using the traditional noble metal oxide coated anode, ruthenium oxide-titanium and the mediator used for the experiment was ferrous sulphate, with sodium chloride as supporting electrolyte. The concentration of sodium chloride was maintained at 5, 8, 12 gm/L. The experiment was carried out in batch recirculation reactor with varied current densities for various flow rates. The study highlighted that in batch reactor set up the best effect of total organic content reduction was found to occur at 3.75 A/dm 2 with flow rate of 20 L/h. The simulated studies were carried out for different volumes of effluent and current densities. A graphical analysis was made between the experimental and simulated values and it was found that both the values are very close.

The Purification, Formulation and Drying of Papain

Papain, a proteolytic enzyme was purified from latex of Carica papaya by a variety of techniques such as two-step salt precipitation, organic solvent precipitation (ethanol) and ion exchange chromatography. Fold purity obtained using ion exchange chromatography was in the range of 4.5 to 5 times as compared to the precipitation techniques. The purified papain was entrapped in ionotropically cross-linked alginate beads, in order to develop formulation for site-specific delivery of papain in intestine. The entrapment efficiency for papain in alginate beads was found to be in excess of 86%. Drying at low temperature and low air velocity results into maximum retention of papain activity; however, drying time increases significantly. The dissolution study shows the possible use of alginate beads for site-specific intestinal delivery of papain. The shelf-life of papain can be improved significantly by entrapment in alginate matrix, which was confirmed by an FTIR study.

Bioremediation of trace cobalt from simulated spent decontamination solutions of nuclear power reactors using E. coli expressing NiCoT genes

Removal of radioactive cobalt at trace levels (approximately nM) in the presence of large excess (10(6)-fold) of corrosion product ions of complexed Fe, Cr, and Ni in spent chemical decontamination formulations (simulated effluent) of nuclear reactors is currently done by using synthetic organic ion exchangers. A large volume of solid waste is generated due to the nonspecific nature of ion sorption. Our earlier work using various fungi and bacteria, with the aim of nuclear waste volume reduction, realized up to 30% of Co removal with specific capacities calculated up to 1 microg/g in 6-24 h. In the present study using engineered Escherichia coli expressing NiCoT genes from Rhodopseudomonas palustris CGA009 (RP) and Novosphingobium aromaticivorans F-199 (NA), we report a significant increase in the specific capacity for Co removal (12 microg/g) in 1-h exposure to simulated effluent. About 85% of Co removal was achieved in a two-cycle treatment with the cloned bacteria. Expression of NiCoT genes in the E. coli knockout mutant of NiCoT efflux gene (rcnA) was more efficient as compared to expression in wild-type E. coli MC4100, JM109 and BL21 (DE3) hosts. The viability of the E. coli strains in the formulation as well as at different doses of gamma rays exposure and the effect of gamma dose on their cobalt removal capacity are determined. The potential application scheme of the above process of bioremediation of cobalt from nuclear power reactor chemical decontamination effluents is discussed.

Crystal Structures of F420-dependent Glucose-6-phosphate Dehydrogenase FGD1 Involved in the Activation of the Anti-tuberculosis Drug Candidate PA-824 Reveal the Basis of Coenzyme and Substrate Binding

The modified flavin coenzyme F(420) is found in a restricted number of microorganisms. It is widely distributed in mycobacteria, however, where it is important in energy metabolism, and in Mycobacterium tuberculosis (Mtb) is implicated in redox processes related to non-replicating persistence. In Mtb, the F(420)-dependent glucose-6-phosphate dehydrogenase FGD1 provides reduced F(420) for the in vivo activation of the nitroimidazopyran prodrug PA-824, currently being developed for anti-tuberculosis therapy against both replicating and persistent bacteria. The structure of M. tuberculosis FGD1 has been determined by x-ray crystallography both in its apo state and in complex with F(420) and citrate at resolutions of 1.90 and 1.95 A(,) respectively. The structure reveals a highly specific F(420) binding mode, which is shared with several other F(420)-dependent enzymes. Citrate occupies the substrate binding pocket adjacent to F(420) and is shown to be a competitive inhibitor (IC(50) 43 microm). Modeling of the binding of the glucose 6-phosphate (G6P) substrate identifies a positively charged phosphate binding pocket and shows that G6P, like citrate, packs against the isoalloxazine moiety of F(420) and helps promote a butterfly bend conformation that facilitates F(420) reduction and catalysis.

Stabilization of As, Cr, Cu, Pb and Zn in soil using amendments – A review

The spread of contaminants in soil can be hindered by the soil stabilization technique. Contaminant immobilizing amendments decrease trace element leaching and their bioavailability by inducing various sorption processes: adsorption to mineral surfaces, formation of stable complexes with organic ligands, surface precipitation and ion exchange. Precipitation as salts and co-precipitation can also contribute to reducing contaminant mobility. The technique can be used in in situ and ex situ applications to reclaim and re-vegetate industrially devastated areas and mine-spoils, improve soil quality and reduce contaminant mobility by stabilizing agents and a beneficial use of industrial by-products. This study is an overview of data published during the last five years on the immobilization of one metalloid, As, and four heavy metals, Cr, Cu, Pb and Zn, in soils. The most extensively studied amendments for As immobilization are Fe containing materials. The immobilization of As occurs through adsorption on Fe oxides by replacing the surface hydroxyl groups with the As ions, as well as by the formation of amorphous Fe(III) arsenates and/or insoluble secondary oxidation minerals. Cr stabilization mainly deals with Cr reduction from its toxic and mobile hexavalent form Cr(VI) to stable in natural environments Cr(III). The reduction is accelerated in soil by the presence of organic matter and divalent iron. Clays, carbonates, phosphates and Fe oxides were the common amendments tested for Cu immobilization. The suggested mechanisms of Cu retention were precipitation of Cu carbonates and oxy-hydroxides, ion exchange and formation of ternary cation–anion complexes on the surface of Fe and Al oxy-hydroxides. Most of the studies on Pb stabilization were performed using various phosphorus-containing amendments, which reduce the Pb mobility by ionic exchange and precipitation of pyromorphite-type minerals. Zn can be successfully immobilized in soil by phosphorus amendments and clays.

The preparation and characterization of cetyltrimethylammonium intercalated muscovite

A new method to prepare alkylammonium–muscovite nanocomposites is reported. The intercalation of alkylammonium into muscovite could be obtained by two steps: the inorganic–inorganic ion exchange and the inorganic–organic ion exchange under hydrothermal condition. The intercalation at different alkylammonium concentration has been studied by elemental analysis, powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR). The cetyltrimethylammonium cations enter the interlayer of muscovite and anchored to the aluminosilicate layer through strong electrostatic interaction. A threshold of cetyltrimethylammonium concentration exists with the maximum ion-exchange percentage of 50%. The arrangement, conformation and orientation of alkylammonium tail and the distribution of headgroups show strong dependence on alkylammonium concentration. At lower alkylammonium concentration, the alkylammonium cations are lying on the aluminosilicate layer to form a monolayer structure, taking disordered conformation and headgroup distribution. With the increase of concentration, the alkyl tails begin to radiate away and stand up from the aluminosilicate surface; meanwhile, the distribution of headgroups become well, and the arrangement and conformation of chains become more ordered. For samples with concentration beyond the threshold, the alkylammonium headgroups are distributed on aluminosilicate layer uniformly, and the alkylammonium chains are in a paraffin-like arrangement with a titled, fully stretched all-trans conformation.

Evaluation of Elution Parameters for Cesium Ion Exchange Resins

Cesium ion exchange is one of the planned processes for treating and disposing of waste at the U.S. Department of Energy Hanford Site. Radioactive supernatant liquids from the waste tanks will undergo ultrafiltration, followed by cesium ion exchange using a regenerable organic ion exchange resin. Two resins, SuperLig®644 and a resorcinol‐formaldehyde resin, are being evaluated for cesium removal and cesium elution characteristics. The main purpose of this study is to optimize the cesium elution to provide a resin that, after undergoing elution, would meet the U.S. Department of Energy/Office of River Protection Project‐Waste Treatment Plant processing and resin disposal criteria. Columns of each resin type were loaded to greater or equal to 90% breakthrough with a Hanford waste stimulant and eluted with nitric acid. The temperature, flow rate, and nitric acid concentration were varied to determine the optimal elution conditions. Temperature and eluant flow rate were the most important elution parameters. As would be predicted based upon kinetic consideration alone, decreasing the eluant flow rate and increasing the temperature provided the optimal elution conditions. Varying the nitric acid concentration did not have a significant effect on the elution completion; however, elutions performed using both high acid concentration (1 M) and elevated temperature (45°C) resulted in resin degradation, causing gas generation and resin bed disruption.