Resin Dowex Research Articles

Selective Synthesis of Vinyl‐ or Alkynyl Chalcogenides from Glycerol and their Water‐Soluble Derivatives

AbstractWe describe here a convenient procedure to synthesize new vinyl chalcogenides in the reaction of dichalcogenides derived from glycerol with terminal alkynes and NaBH4, where polyethylene glycol‐400 (PEG‐400) is the solvent at 30 °C in a N2 atmosphere. In addition, we report an interesting result for the synthesis of alkynyl chalcogenides using the same substrates with EtOH as the solvent. In both protocols, the corresponding products were obtained in good yields with high selectivity and tolerated a range of terminal alkynes. The treatment of these compounds with acidic cation exchange resin Dowex‐(H+) produced new water‐soluble organochalcogen compounds.

Sorption Behavior of Dowex PSR-2 and Dowex PSR-3 Resins of Different Structures for Metal(II) Removal

ABSTRACTThe sorption behavior of palladium(II) (Pd(II)) onto strongly basic anion exchange Dowex resins was studied depending on the concentration of hydrochloric acid (0.1–6.0 M HCl–100 mg Pd(II)/L), concentration of hydrochloric and nitric(V) acids (0.1–0.9 M HCl–0.9–0.1 M HNO3–100 mg Pd(II)/L), and the time of contact of the solution with the anion exchange resin in the batch mode. Similar research was carried out also for the base metal ions such as cobalt(II) (Co(II)), copper(II) (Cu(II)), nickel(II) (Ni(II)), and zinc(II) (Zn(II)). The sorption process was also examined depending on the initial Pd(II) concentration, agitation rate, bead size distribution, and temperature. Pd(II) sorption was also checked in the column mode. The equilibrium and kinetic characteristics of the sorption of Pd(II) with the Dowex PSR-2 and Dowex PSR-3 anion exchange resins were determined. The possibilities of Pd(II) elution and reuse using the batch method was exploited. Pd(II) and Zn(II) sorption on the Dowex resins is time and concentration of acids dependent. Evaluating the determination coefficients, the kinetic studies showed that the pseudo-second-order equation and the Langmuir model described the data more appropriately than others. The maximum sorption capacity was 165.15 mg Pd(II)/g for Dowex PSR-2 and 184.39 mg Pd(II)/g for Dowex PSR-3. Dowex resins give quantitative Pd(II) removal from diluted acidic solutions.

Incorporation of zero valent iron nanoparticles in the matrix of cationic resin beads for the remediation of Cr(VI) contaminated waters

The objective of present study was to obtain the fixation of nano zero valent iron (nZVI) particles on a permeable matrix and evaluate the performance of this composite material for the removal of Cr(VI) from contaminated waters. The experiments were carried out using the cationic resin Dowex 50WX2 as porous support of the iron nanoparticles. The work was carried out in two phases. The first phase involved the fixation of nZVI on the resin matrix. The resin granules were initially mixed with a FeCl3 solution to obtain the adsorption of Fe(III). Then the Fe(III) loaded resin (RFe) was treated with polyphenol solutions to obtain the reduction of Fe(III) to the elemental state. Two polyphenol solutions were tested as reductants, i.e. green tea extract and gallic acid. Green tea was found to be inefficient, probably due to the relatively big size of the contained polyphenol molecules, but gallic acid molecules were able to reach adsorbed Fe(III) and reduce the cations to the elemental state. The second phase was focused on the investigation of Cr(VI) reduction kinetics using the nanoiron loaded resins (R-nFe). It was found that the reduction follows a kinetic law of first order with respect to Cr(VI) and to the embedded nanoiron. Compared to other similar products, this composite material was found to have comparable performance regarding reaction rates and higher degree of iron utilization. Namely the rate constant for the reduction of Cr(VI), in the presence of 1 mM nZVI, was equivalent to 1.4 h of half-life time at pH 3.2 and increased to 24 h at pH 8.5. The degree of iron utilization was as high as 0.8 mol of reduced Cr(VI) per mole of iron. It was also found that this composite material can be easily regenerated and reused for Cr(VI) reduction without significant loss of efficiency.

Research of efficiency of water purification-exchange resin from iron compounds using modified filter media

Recently, the modified media have become widely used in the processes of iron removal from water. These media are based on the natural granular material with a catalytically-active surface layer, which promotes a more efficient oxidation of iron ions. However, their application raises some problems associated with restoring their oxidative capacity, reliability and duration of use. The paper presents the results of removal of iron ions from water by catalytic oxidation. The method of modifying the filter medium for iron removal from water is developed. The efficiency of iron oxidation with the zeolite and cation-exchange resins modified with iron and manganese compounds is evaluated. It is shown that the modified zeolite is ineffective compared to the modified cation-exchange resin Dowex Mac-3. The manganese-modified cation-exchange resin provides efficient removal of iron ions from water. The iron removal degree was initially 97 % and then gradually decreased to 86 %. The iron concentration in the treated water did not exceed 0.3 mg/dm 3 . When using the iron-modified cation-exchange resin, the iron concentration decreased from 15 to 0.1–0.2 mg/dm 3 . The iron removal degree was more than 99 % over a long time. It is found that efficient iron oxidation in water occurs in the presence of sufficient oxygen, that is pre-aeration is required. The drawback of the proposed modified media is a slight loss of oxidative capacity after filter washing.

Preparation of Some Mercurated Dowex Resins and Study of Their Industrial Applications For Desulfurization

Preparation of Some Mercurated Dowex Resins and Study of Their Industrial Applications For Desulfurization

Application of response surface methodology and artificial neural network: modeling and optimization of Cr(VI) adsorption process using Dowex 1X8 anion exchange resin.

We report the adsorption efficiency of Cr(VI) on a strong anionic resin Dowex 1X8. The Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analysis of this adsorbent were investigated. Response surface methodology was applied to evaluate the main effects and interactions among initial pH, initial Cr(VI) concentration, adsorbent dose and temperature. Analysis of variance depicted that resin dose and initial pH were the most significant factors. Desirability function (DF) showed that the maximum Cr(VI) removal of 95.96% was obtained at initial pH 5, initial Cr(VI) concentration of 100 mg/L, resin dose of 2 g and temperature of 283 K. Additionally, a simulated industrial wastewater containing 14.95 mg/L of Cr(VI) was treated successfully by Dowex 1X8 at optimum conditions. Same experimental design was employed to develop the artificial neural network. Both models gave a high correlation coefficient (RRSM(2) = 0.932, RANN(2) = 0.996).

Interfacial reaction using particle-immobilized reagents in a fluidized reactor. Determination of glycerol in biodiesel

A novel fluidized beads strategy for utilization of particle-immobilized reagents in flow analysis was developed in this study. The performance of the suggested strategy was demonstrated by the determination of glycerol in biodiesel. This analytical task was used as a proof-of-concept example. The method is based on on-line extraction of glycerol from biodiesel into aqueous stationary phase of extraction-chromatographic column, followed by elution and spectrophotometric determination in the form of copper glycerate formed in a fluidized reactor of stepwise injection system. The floating of cation exchange resin Dowex® 50WX4, saturated with Cu(II) ions in liquid phase, was accomplished by air-bubbling. The linear range was from 100 to 1000 mg kg−1, and the limit of detection, calculated as 3s of a blank test (n = 5), was found to be 30 mg kg−1. The method was successfully applied to the analysis of biodiesel and biodiesel-blend (B 20) samples.

Removing nitrate from water using iron-modified Dowex 21K XLT ion exchange resin: Batch and fluidised-bed adsorption studies

Abstract Elevated concentrations of nitrate in surface waters can cause eutrophication, while in drinking water they pose a threat to human health, especially causing blue baby syndrome in infants. An anion exchange resin – Dowex 21K XLT – was surface modified by incorporating Fe (Dowex-Fe) and tested to remove nitrate from aqueous solutions in batch and fluidised-bed adsorption experiments. Solution pH in the 4.0–7.5 range had no effect on nitrate adsorption. The adsorption data at pH 6.5 fitted well to the Langmuir model with maximum adsorption capacities of 27.6 mg N/g, and 75.3 mg N/g for Dowex and Dowex-Fe resins, respectively. Energy dispersion spectrometry and zeta potential measurements indicated that the increase in adsorption due to Fe impregnation was caused by additional surface positive charges induced on the resin by Fe. In both batch and fluidised-bed experiments, nitrate adsorption capacity declined markedly when sulphate was added, but phosphate and chloride additions had little effect. Batch kinetic data fitted well to the pseudo-first, pseudo-second and homogeneous surface diffusion models. Data from the fluidised-bed experiments satisfactorily fitted to the Thomas and plug-flow models. More than 95% of adsorbed nitrate was desorbed by 1 M KCl in all three adsorption/desorption cycles and the resins were successfully regenerated in each cycle with little reduction in adsorption capacity. No significant reduction in the Fe content of Dowex-Fe occurred during the regeneration.

Removal of phosphorus by a high rate membrane adsorption hybrid system

Membrane adsorption hybrid system (MAHS) was evaluated for the removal of phosphate from a high rate membrane bioreactor (HR-MBR) effluent. The HR-MBR was operated at permeate flux of 30L/m2h. The results indicated that the HR-MBR could eliminate 93.1±1.5% of DOC while removing less than 53% phosphate (PO4-P). Due to low phosphate removal by HR-MBR, a post-treatment of strong base anion exchange resin (Dowex∗21K-XLT), and zirconium (IV) hydroxide were used as adsorbent in MAHS for further removal of phosphate from HR-MBR effluent. It was found that the MAHS enabled to eliminate more than 85% of PO4-P from HR-MBR effluent. Hence, HR-MBR followed by MAHS lead to simultaneous removal of organics and phosphate in a reliable manner. The experiments were conducted only for a short period to investigate the efficiency of these resins/adsorbents on the removal of phosphorus and high rate MBR for organic removal.

Removal of Ni(II), Zn(II) and Pb(II) from aqueous solutions using cation-exchange resin in fixed-bed column

Breakthrough curves for the removal of Ni(II), Zn(II), and Pb(II) from aqueous solutions using cation exchange resin (Dowex 50W) were determined at dynamic conditions in a fixed-bed column under ambient temperature. The experiments and data obtained were designed and analyzed using response surface methodology, respectively. Three operating parameters: flow rate (15–25 mL min−1), pH (3–9), and bed height (3–5 cm) were investigated. Fixed-bed adsorption models namely Thomas model and Bohart–Adam model were adopted to describe the dynamics of metal adsorption in the column. The obtained experimental data were fitted to these models based on the kinetic constant kBA (mg min cm−3), kTH (cm3 mg−1 min), the maximum amount of metal exchange N0 (mg cm−3), and the maximum adsorption capacities qtm (mg), accordingly. The Thomas model was found to best fit all the experimental conditions studied with correlation coefficients of 0.91, 0.97, and 0.92 for Ni(II), Zn(II), and Pb(II), respectively.

Multicolumn solid phase extraction with hybrid adsorbent and rapid determination of Au, Pd and Pt in geological samples by GF-AAS

A novel hybrid adsorbent (HA) composed of cellulose fiber, activated carbon, and anion exchange resin Dowex 1×8 was prepared for the preconcentration and separation of noble metals, namely, gold (Au), palladium (Pd) and platinum (Pt), in geological samples. The optimal experimental parameters, such as flow rate, sample volume and interfering ions, were investigated. The accuracy of the method was confirmed by added/found method for tap and sea water, and evaluated by analyzing certified reference materials with good agreement. Under the optimal experimental conditions, the detection limits (3σ criteria) of the developed technique were 0.008ngmL−1 (Au), 0.017ngmL−1 (Pd) and 0.014ngmL−1 (Pt) and the sample throughput reach to 30 samples every eight hours. Moreover, the adsorption capacity of HA for Au, Pd and Pt was determined to be 48.2, 35.9 and 29.8mgg−1, respectively.

Impact of sediment grain-size and biofilm age on epipelic microphytobenthos resuspension

Intertidal zones are dynamic areas, where tidal currents and wind-induced waves are responsible of resuspension of the sediment and associated microphytobenthos (MPB). Sediment composition (mud–sand mixtures) and MPB biofilm age are two major components involved in resuspension of epipelic microphytobenthos in muddy areas. However, their relative role in resuspension phenomenon must be better understood in controlled conditions. In this study, three mud–sand mixtures (Pure mud M1, 75% mud/25% sand M2 and 50% mud/50% sand M3) were tested with an epipelic MPB biofilm of different ages (3, 6 and 9days after inoculum) using an erodimeter flume. The biofilm biomass, physiological state, photosynthetic parameters and Extracellular Polymeric Substances (EPS) were surveyed as well as water content and ammonium concentration in the sediment. Chl a content and Suspended Particular Inorganic Matter (SPiM) erodability differed between treatments, biofilm being able to be eroded before sediment when it is well constituted (especially in pure mud M1). Between day 3 and day 9 of culture, biofilm age did significantly affect critical thresholds for Chl a erosion and sediment resuspension for mud–sand mixtures (M2 and M3). Sediment resuspension seemed to be also driven by physical constraints like differential compaction and vertical sand segregation as a function of mud content. Indeed, grain-size was the main factor involved in MPB resuspension phenomenon, with an optimum reached near a equilibrate ratio between mud and sand (50% mud–50% sand). Proteins of the EPS bound fraction (extracted with dowex resin) appeared to have a critical role in the pioneering stages of biofilm installation, allowing its formation in a less favorable environment caused by sand enrichment (mixtures M2 and M3). This effect of bound EPS must be mediated by an increasing cohesion and lowering sediment permeability. Carbohydrate content of the bound EPS fraction was directly related to the sediment (SPiM) erodability, independently from mixture type or biofilm age.

Positron and γ-ray intensities in the decay of 45Ti

Abstract To evaluate the PET-imaging properties of the promising positron emitter 45Ti, its β +- and γ-ray intensities were measured. Use of the cation-exchange resin DOWEX 50W×8 (H+-form) enabled the isolation of radiochemically pure, no-carrier-added 45Ti from “bulk” scandium after proton bombardment. Thin, no-carrier-added 45Ti samples were prepared. The combination of γ-ray and X-ray spectrometry with γγ-coincidence counting allowed for the first time the experimental determination of the positron intensity as (85.67 ± 2.23)% and the absolute intensity of the 720.22 keV γ-ray as (0.1171 ± 0.0057)%.

In-line extraction of REE from Dihydrate (DH) and HemiDihydrate (HDH) wet processes

Phosphate rock (PR) contains traces of rare earth elements (REEs), ranging from 100 to 1000μg/g. However, REE may be regarded as s secondary source for REE since large tonnages of PR are mined annually and used in phosphoric acid production.In this work, batch leaching tests were conducted to simulate (DH) and (HDH) wet processes in order to determine REE distribution in the product acid and phosphogypsum (PG). Then REE was extracted in-line during PR acidulation using Tributyl Phosphate (TBP) diluted with kerosene and ion exchange resin DOWEX- 50WX8 (−300+150μm).It was found that in DH process, approximately 80% of the feed REE reported to PG; about 65% of them were LREE while HREE constitute 64% of REE reported to the product acid. On the other hand, REE reported to PG in HDH process was slightly higher than DH; approximately 84% of the REE was reported to PG; 62% of them were LREE while 70% of REE reported to product acid was HREE.It was also found that REE was efficiently extracted by ion exchange resin than TBP solvent: REE in PG was increased by 230%, from 335.3 to 1106.6μg/g, with ion exchange resin compared to 45% REE reduction (from 335.3 to 182.27μg/g) when TBP solvent was added. The main challenge is to efficiently separate the loaded resin beads from the fine grained PG and acid insoluble residuals.

Behavior of cation-exchange resins employed as heterogeneous catalysts for esterification of oleic acid with trimethylolpropane

Four cation-exchange resins (Dowex 50wx2, Amberlyst 36, Purolite CT482 and Purolite CT275DR) were investigated as catalysts in the esterification of oleic acid (OA) with trimethylolpropane (TMP). All four resins accelerated the reaction kinetics. The results showed that in a solvent-free system, the gel-type resin Dowex 50wx2 must be pre-swollen prior the reaction to achieve high catalytic performance. Contrary, the macro-reticular Amberlyst 36, Purolite CT482 and Purolite CT275DR do not need any pre-treatment to be active. The latter is due to the high crosslinking degree of these resins. Recyclability tests showed that the resins slightly lose their activity after the first use but retain stable activity during the further uses. The activity decay of the recycled resins is referred to the partial blocking of the active sites by the co-produced water. Additional studies confirmed the high stability of the chosen resins toward leaching in polar medium. Overall, both high stability and possibility of reusing through still high catalytic activity make the resins attractive candidates as heterogeneous catalysts for such complex industrial process.

Effect of pH and metal ions on DPPH radical scavenging activity of tea

The 2,2′-diphenyl-1-picrylhydrazyl (DPPH) assay is commonly applied for the estimation of antioxidant activity of plant extracts. This article discusses the effect of a sample pH and the presence of metal ions on the results obtained using DPPH method for several tea infusions. Higher radical quenching was observed in less acidic media. The impact of metal ions depends of the types of metal ion and its concentration. Quercetin and epigallocatechin gallate were less efficient in the reaction with DPPH in the presence of Al(III). Desalting process using cation-exchange resin Dowex 50Wx8 decreased the content of metal ions in all studied tea infusions. The DPPH scavenging activity of the effluents after this process were higher than those of the primary extracts and this may be related to the actual antioxidant capacity of these samples.

Ion Exchange and Thin Layer Chromatographic Separation and Identification of Amino Acids in a Mixture: An Experiment for General Chemistry and Biotechnology Laboratories

A multiday laboratory exercise is described that is suitable for first-year undergraduate chemistry, biochemistry, or biotechnology students. Students gain experience in performing chromatographic separations of biomolecules, in both a column and thin layer chromatography (TLC) format. Students chromatographically separate amino acids (AA) in an unknown mixture using a small column of Dowex-50 resin. The AA elution profile is determined by graphical analysis of a rapid ninhydrin microplate spectrophotometric assay that converts the colorless AA into colored ninhydrin derivatives. Column fractions corresponding to elution “peaks” are further analyzed by TLC on silica gel plates alongside AA standards. Visualization of AA migration on TLC is accomplished with a ninhydrin dipping protocol. Students use their chromatography data, structural information about the resin and the various AA, and their knowledge of intermolecular attractions and acid–base chemistry to determine the identity of the AA in their unknown mixture.

Synthesis and characterization of porous WO3–SnO2 nanomaterials: An infrared study of adsorbed pyridine and dimethyl methylphosphonate

High surface area porous W/Sn oxide nanomaterials were prepared via water/oil based (W/O) emulsion. Tungstic acid solution was generated by cation exchange of sodium tungstate in acidic Dowex resin. The acid was then mixed with a clear homogeneous aqueous N-cetyl trimethyl ammonium bromide (CTAB) solution followed by a slow addition of 0.2M SnCl4 solution. The mixture was stirred for 24h and then subjected to slow calcination at 500°C. The prepared materials were characterized using SEM-EDX, BET surface area, and sorption of nitrogen and water. Fourier transform infrared spectroscopy (FTIR) was used to characterize the surface acidic properties using pyridine vapor as a probe. The materials were then tested toward the Dimethyl methylphosphonate (DMMP) adsorption at various temperatures using infrared spectroscopy. At elevated temperatures, the desorption of DMMP from WO3 and SnO2 surfaces results in forming methyl phosphonate that strongly bounds on the metal oxide surfaces. In contrast, the FTIR spectra showed that the adsorbed dimethyl methylphosphonate (DMMP) on the mixed W/Sn oxide powders can be molecularly desorbed without any decomposition.

ChemInform Abstract: Carbon—Carbon Coupling Reactions Catalyzed by Supported Pd Porphyrins.

AbstractThe shown Pd‐complex (PPC) is supported on Dowex and Amberlite ion‐exchange resins and is used in Heck and Suzuki cross coupling reactions.

Purification of 89Sr source obtained from 89Y(n, p) 89Sr by ion-exchange chromatography using tri-sodium tri-meta phosphate (SMP) as eluant

89Sr was produced via 89Y(n, p) 89Sr using yttria as target in Fast Breeder Test Reactor (FBTR), Kalpakkam, India. A radiochemical procedure has been developed for the separation of bulk yttrium using TBP by solvent extraction followed by purification of 89Sr source by ion exchange chromatography using the cation exchange resin Dowex 50WX8 (100–200 mesh) and nitric acid of variable molarity as eluant. The present study establishes the purification of 89Sr source from the other radionuclidic impurities like 88Y, 65Zn, 54Mn, 60Co, 86Rb, 192Ir, 103Ru, 113Sn, 139Ce, 160Tb, 154Eu etc. produced during the irradiation of yttria by using the complexing agent tri-sodium tri-meta phosphate (SMP) in nitric acid medium instead of nitric acid alone as an eluant. The purification was achieved by using 0.1 M SMP as complexing agent which was optimized based on the distribution ratio data and final elution of Sr fraction was obtained in nitric acid medium. This resulted into a faster purification of 89Sr source in a smaller volume of eluant. Purity of Sr source from the cross contamination of the complexing agent SMP was also ensured.