The extraction of uranium from acidic solutions by Adogen impregnated open cell polyurethane foam sponge

Open cell polyurethane foam coated with long chain tertiary amines (Adogen) has been shown to be an effective extractant for uranium in acidic solutions (3>pH>1). With dodecyl alcohol present uranium extraction at pH<1 is effective. The coated foam allowed column flow extraction at high flow rates but capacity studies indicated that only a fraction (about 1/3 to 1/2) of the amine was available for the complexation of the uranium. Interference of some common metal cations indicated that only Co(II) showed a significant adverse effect on the uranium extraction.     

Extraction chromatography of thorium ion by solid phase impregnated resins containing bi-functional organic extractants</p> </p>

Summary Macroporous methyl methacrylate polymeric resin (XAD-7) was investigated incorporating both acidic organophosphorous extractant (cyanex-301) and one neutral extractant from the followings: dibenzo 18 crown 6 (DB18C6), 18 crown 6 (18C6) and 15 crown 5 (15C5). The sorption behavior of the solvent impregnated resin (SIR) towards thorium ion, including batch equilibrium, and kinetic operation are described. Different factors affecting the uptake of metal ions and hence, the separation efficiency of the impregnated resins were investigated. The maximum uptakes of Th⁴⁺ were found to be 62.9, 66.7 and 92.6% for DB18C6, 18C6 and 15C5, respectively. Synergistic extraction of various CE towards thorium ion was tested with cyanex-301 to enhance the sorption capacity as well as the selective separation efficiency. A relatively high capacity of the chelating resin towards tetravalent thorium was found. The capacities of the co-impregnated resins were found to be 2.11, 2.42 and 3.85 mmol/g for DB18C6, 18C6 and 15C5, respectively. The impregnated resin containing cyanex-301 and 15C5 can be utilized for selective separation and pre-concentration of thorium ion from nitrate medium in the presence of several interfering metal ions.</p> </p>     

Extraction of technetium by DB18C6 and 18C6 into nitrobenzene and acetylacetone from an aqueous phase containing NaBH4

The extraction of technetium by DB18C6 and 18C6 into nitrobenzene and different solvents from aqueous phase containing NaBH₄ was investigated. The experimental data indicate that the main extracted species have the formulas TcO/OH/₂.CE or 2TcO/OH/₂.3CE, where CE refers to the crown ethers. The effects of crown ether concentration, pH and organic solvent on the distribution ratio are discussed. The extent of extraction from different solvents decreases in the order nitrobenzene >acetylacetone>1-butanol>toluene> benzene.     

Chiral separation of amino-alcohols using extractant impregnated resins

The performance of extractant impregnated resin (EIR) technology for chiral separation of amino-alcohols has been investigated. Phenylglycinol was selected as an archetype model enantiomer and azophenolic crown ether was used as a versatile enantioselective extractant. 1-Phenyloctane was selected as a suitable solvent for this application because of its very low solubility in water. The extraction system was first evaluated by liquid-liquid equilibrium experiments. It was shown that crown ether dissolved in 1-phenyloctane has an intrinsic selectivity of 11.5. However, due to very low solubility of phenylglycinol in 1-phenyloctane, the overall capacity of the crown ether solution in 1-phenyloctane is limited. The extractant solution was immobilized in macroporous polypropylene particles. Competitive sorption isotherms were obtained from batch experiments and successfully described with a predictive model based on the complexation constants and partitioning ratios, either obtained from literature or from independent experiments. The equilibrium selectivity of these EIRs approaches the intrinsic selectivity for low phenylglycinol concentrations. The dynamic behaviour and stability of the system were examined in column experiments. Breakthrough profiles as well as the elution curves of the R enantiomer are less sharp than those of the S enantiomer proving that the R enantiomer is strongly retained on the column. Separation of phenylglycinol enantiomers is favoured by using lower feed flow rates. The column was regenerated by water with only atmospheric carbon dioxide dissolved which proved to be sufficient. After several cycles the breakthrough profiles remain unchanged suggesting that these EIRs will be sufficiently stable.     

Effects of phosphate and Cr3+ on the sorption and transport of uranium(VI) on a silica column

Six column experiments were performed and seven breakthrough curves (BTCs) and seven displacement (desorption) curves (DPCs) of phosphate and U(VI) were obtained, which demonstrated the effects of phosphate and Cr³⁺ on the sorption and transport of U(VI) on a silica column at pH 3 and uranium concentration 10⁻⁵–10⁻⁶ mol/L of the influent. It was found that in the presence of phosphate sorbed preliminarily on the silica column, the amount of U(VI) sorbed on this column is significantly increased owing to the interaction of U(VI) with phosphate sorbed as compared with that in the absence of phosphate, and the breakthrough and the mean residence time of U(VI) on this column are similar to those in the absence of phosphate. While the effect of simultaneous injection of Cr³⁺ on the retardation of U(VI) on the silica column, the maximum concentration of BTC and the amount of U(VI) sorbed was found to be insignificant. Transport and sorption studies of U(VI) are important, since all uranium isotopes are radioactive, there is a need to understand the potential for migration away from radioactive waste storage and mill tailing sites.     

Preconcentration and separation of acaricides by polyether based polyurethane foam

This paper reports the preconcentration of some dissolved organic phosphorous and chlorinated acaricides in water by porous polyether based polyurethane foam. Preliminary screening tests on the retention of the tested compounds, i.e., dicofol and bromopropylate, by polyether foams indicated that a very high percent removal of the tested species was obtained. The retention rate was found fast and reaches equilibrium in a few minutes. The various parameters, e.g., pH, extraction media, shaking time, salt effect, temperature and sample volumes affecting the preconcentration of the tested species by the unloaded foam, trioctylamine and trimethylphosphate treated foam have been optimized via batch modes of separation. The unloaded foams were employed in column modes for the retention and recovery of the tested species. The sorption efficiency and recovery of the compounds by the unloaded foams column were found to be up to 97.5%. The height equivalent to a theoretical plate (HETP) obtained by the unloaded foam was found to be in the range 1.1-1.3 ± 0.2 mm. The sorption mechanism of the tested compounds by the foams was discussed.     

Retention profiles of some commercial pesticides, pyrethroid and acaricide residues and their application to tomato and parsley plants

This work deals with the preconcentration of some water soluble pesticides, pyrethroids and acaricides by polyurethane foams. The retention profiles of the tested species were found quickly and reached equilibrium in a few min. Various parameters — e.g. pH, extraction media, shaking time, salt effect, temperature and sample volume — affecting the preconcentration of the tested species by the unloaded foams and tri-n-octylamine and tri-n-methylphosphate treated foams were optimized. The unloaded foams were employed in a column mode to study the quantitative retention and recovery of the tested species. The sorption efficiency and recovery of the compounds by the unloaded foam column were found to be up to 99.5%±2.1. The height equivalent of a theoretical plate for the unloaded foam column was found to be in the range 1.9–2±0.2 mm. The sorption mechanisms of the tested compounds by the foams are discussed. Analysis of N, P, Na, K, Cu, Zn, Mn, Fe, humidity, wet and dry mass of tomato and parsley untreated and sprayed for different time intervals — i.e. 24, 72 and 120 h — with Chlorpyrifos, was carried out.     

Kinetics and retention characteristics of some nitrophenols onto polyurethane foams

The kinetics of sorption of the nitrophenols by the unloaded polyurethane foams (PUFs) were found fast, reached equilibrium in few minutes and followed a first-order rate equation with an overall rate constant k in the range (0.16-0.21)±0.01 min⁻¹. The retention of the tested nitrophenols by the unloaded foams is consistent with the “solvent extraction” mechanism. However, the sorption also followed Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherms. The mean free sorption energy of the nitrophenols onto the PUF was found equal to 7.5±0.4 kJ/mol, which reflects physical sorption. Thus, a dual-mode involves both absorption related to solvent extraction and an added component for surface adsorption seems a more likely sorption mechanism model. While a dual-mode sorption model explains the observed retention behavior, the data suggest that, solvent extraction plays a much larger role than the added component for surface adsorption. The sorption and recovery percentages of the nitrophenols from fresh, natural and industrial wastewater by the proposed unloaded foam columns were quantitatively achieved. The height equivalent to theoretical plates (HETP), N, the breakthrough capacity and the critical capacity for the unloaded foam columns were found in the range of (0.8-1.1)±0.6 mm, (94-132)±3, 3.2-4.02 and 1.5-2.67 mg/g, respectively. The method was successfully applied for the retention and recovery of the tested nitrophenols spiked to fresh and industrial wastewaters.     

Recovery of uranium by polyurethane foam impregnated with 5,8-diethyl-7-hydroxy-6-dodecanone oxime

Sorption of uranium(VI) has been inbestigated using an open-cell plyurethane foam impregnated with 5,8-diethyl-7-hydroxy-6-dodecanone oxime (LIX 63). Above pH 4.5 more than 99% of uranium is sorbed onto the LIX 63 impregnated foam, and uranium can be desorbed with a dilute acid from the foam. The sorption capacity for uranium increases linearly with increasing concentration of impregnated LIX 63. Quantitative removal of uranium from salt solutions was accomplished.     

Sorption of iron(III) and iron(II) from acidic chloride solutions by polyether and polyester type polyurethane foams

Summary Iron(III) is sorbed by polyether type open-cell polyurethane foams from HCl solutions of 4 mol/l or higher. The capacity of the foams is around 50 mg·l^–1. The iron (III) sorbed can be eluted from the foam with 0.01 mol/l HCl or distilled water. An optimization of the sorption conditions showed that the process can be used for analytical applications. The polyurethane foam sorbents examined did not sorb iron(II). The mechanism of sorption by polyether foams seems to follow a mechanism similar to that of the extraction of iron(III) by etheric solvents.     

Extraction of uranium(VI) with non-plasticized and TBP-plasticized polyurethane foam sorbents loaded with dibenzoylmethane

Studies have shown that plots of the log of the distribution ratio versus pH for the distribution of uranium(VI) between non-plasticized and TBP-plasticized dibenzoylmethane-loaded polyurethane foams and dilute aqueous uranium(VI) solutions have a limiting slope of 0.6 at equilibrium pH values 4 and reach a maximum distribution constant at about pH 6.0. The results indicate that the extracted complex is a simple chelate, UO₂Me₂, where HMe denotes dibenzoylmethane. Plasticization of the foam with TBP has been found to significantly enhance the rate of extraction.     

Extraction of azo dyes by polyurethane foam

The extraction of 12 closely related mono-azo dyes by polyester and polyether-type polyurethane foams was studied to gain more information regarding the mechanism of the extraction of organic compounds. The effects on extraction of solution pH, dye concentration and salt concentration were investigated. It was found that the extraction of the dyes involved a neutral zwitterionic species and is highly dependent on the parameters studied. The dependency of the extraction on these parameters can be explained in a manner consistent with solvent extraction; however, the dual-mode sorption mechanism seems a more likely model. This mechanism involves both absorption related to solvent extraction, and an added component for surface adsorption. While the dual-mode sorption model explains the observed extraction behaviour, the data suggest that surface adsorption plays a much larger role than previously considered.     

An excellent arsenic(V) sorption behavior of p-tert-butylcalix[8]areneoctamide impregnated resin

The present article describes the arsenic(V) extraction behavior of p-tert-butylcalix[8]areneoctamide (3) and of a resin (4) impregnated with 3. Liquid–liquid and solid–liquid (column sorption) extraction studies were carried out to optimize various experimental parameters such as pH, extraction effeciency and column stability. Thermodynamic studies based upon Temkin and Flory-Hugins models reveal that the sorption was spontaneous and exothermic. The values of correlation coefficients (R2) show that Langmuir and Freundlich isotherm models are best fit to describe the sorption equilibrium. Application of 4 to real samples indicates a slight decrease (5-7%) in extraction efficiency of 4 because of high concentration of total dissolved salts (TDS). It is deduced that 4 is highly effective for the removal of arsenic(V) at a wide range of pH and attains a maximum value, i.e. 99% at pH 4. The impregnated resin is easy to synthesize from cheap materials. It is more efficient and easily regenerable as compared to already reported resins.     

Combination of size selective binding ability of 18-crown-6 dissolved in aqueous phase and extractive properties of an amic acid; toward enhancement of rare earths separation

The separation of La(III), Eu(III) and Er(III) ions by an amic acid, N,N-dioctyldiglycolamic acid (HL), dissolved in carbon tetrachloride has been improved in the presence of 18-crown-6 (18C6) in aqueous phase as a selective masking agent. The interaction between the studied metal ions and 18C6 resulted a shift in the extraction curve of the studied metal ions versus pH toward higher pH region. The displacement of the extraction curves was more pronounced for lanthanum ions and was varied as La(III) > Eu(III) > Er(III). This order of complexing ability of 18C6 toward the studied ions was attributed to the size adaptation of the ions and that of the crown ether cavity. The stability constants of the lanthanide–crown ether complexes in aqueous phase were evaluated. The influence of temperature on the extraction of studied metal ions from aqueous phase in the absence and the presence of 18C6 was tested in the range 298–308 K. This investigation allowed evaluating the thermodynamic parameters associated with the extraction process and those of the complexation of cations by 18C6 in the aqueous phase.     

Effects of phosphate and fulvic acid on the sorption and transport of uranium(VI) on silica column

Column experiments were performed, breakthrough curves (BTCs) and displacement curves (DPCs) were obtained of uranium(VI) in the absence and presence of phosphate or fulvic acid individually and simultaneously which demonstrated the effects of phosphate and fulvic acid on the sorption and transport of U(VI) in a silica column at pH 3.7 and U(VI) concentration of 5·10⁻⁶ mol/L. It was found that in the presence of phosphate or fulvic acid sorbed preliminarily on the silica column, the amount of U(VI) sorbed increased significantly and the transport of U(VI) delayed significantly relative to that in the absence of phosphate or fulvic acid. Moreover, in the presence of phosphate and fulvic acids sorbed preliminarily and simultaneously on the silica column, the amount of U(VI) sorbed on the silica column is significantly increased again relative to that in the presence of phosphate or fulvic acid individually. Transport studies of U(VI) are important, since all uranium isotopes are radioactive, and uranium contamination of soils and groundwaters occurs at mining and mill sites. A fundamental understanding of the transport behavior of U(VI) in the water-mineral systems is necessary for accurate risk assessments.     

Sorption behaviour of uranium(VI) with N,N-dibutyl-N'-benzoylthiourea Impregnated in Amberlite XAD-16

The sorption of U(VI) by N, N-dibutyl, N'-benzoylthiourea (DBBT) impregnated resin has been studied. DBBT impregnated resin was prepared by direct adsorption of chelating ligand onto macroporous support, Amberlite XAD-16. The adsorption of DBBT on the macroporous support is shown by FTIR spectroscopy to be the result of only weak chelating ligand-support interactions. Parameters such as the pH effect on the sorption of uranium, the sorption capacity of the impregnated resin, the stripping of uranium and the effect of coexisting ions were investigated by batch experiments. The results demonstrated that uranium(VI) ions, at pH 4.5-7 could be sorbed completely using 0.1 g Amberlite XAD-16 resin loaded with DBBT. The sorption capacity of the impregnated resin is 0.90 mmol uranium(VI) g(-1). Quantitative recovery of U(VI) is achieved by stripping with 0.1 M HNO(3). The method was applied to the determination of uranium in synthetic samples. The precision of the method was 2.4 RSD% in a concentration of 1.20 mug ml(-1) for ten replicate analysis.     

用PAN-聚氨酯泡沫富集天然水中铜、锌、镉的原子吸收分析

本文研究了PAN负载的聚氨酯泡沫在静态法和动态法对水溶液中Cu、ZnCd离子的萃取行为,同时试验了pH、阴离子以及流速的影响。回收率试验表明,该法能定量捕集天然水中Cu、Zn、Cd离子,结果令人满意。     

Ion-pair extraction of uranyl ion from aqueous medium using crown ethers

Ion-pair extraction behaviour of uranyl ion from aqueous solutions was studied at pH 3.0 employing crown ethers viz. benzo 15 crown 5 (B15C5), 18 crown 6 (18C6), dibenzo 18 crown 6 (DB18C6), and dibenzo 24 crown 8 (DB24C8) in chloroform as the organic phase and picric acid as the organophilic counter anion. The stoichiometry of the extracted species corresponded to [UO₂(crown ether)_n]²⁺·[pic⁻]₂ where n=1.5 for benzo 15 crown 5 and 1 for 18 crown 6 as well as dibenzo 18 crown 6. Adducts of DB24C8 could not be observed as practically no extraction was possible using this reagent. The separation behaviour of fission products from an irradiated uranium target was also studied. An interesting observation on the separation of trivalent lanthanides from uranyl ion is reported.     

Sorption of Cobalt on Modified Silica Gel Materials

Various silica gel materials were chemically modified with imidazole, diaza-18-crown-6 (DA18C6) and dibenzod-18-crown-6 (DB18C6). The degree of functionalization of the covalently attached molecule was calculated from C, H, N analysis and ranged between 0.270 and 0.552 mmol/g (for sorbents with imidazole) and between 0.043 and 0.062 mmol/g (for sorbents with DA18C6 and DB18C6). The degree of functionalization depends on the reflux time and silica gel matrix used. Experimental sorption capacity ranged between 0.038 and 0.228 mmol/g (for sorbents with imidazole) and between 0.019 and 0.050 mmol/g (for sorbents with DA18C6 and DB18C6). Synthesized hexagonal mesoporous silica matrix MCM-41 with uniform pore diameter <40 Å was used too. Change of pore diameters of silica gel support to larger pores should have a positive influence on access of cobalt ion to sorption centers to increase of sorption capacity of sorbents. The sorption kinetics of cobalt and the influence of cobalt concentration, pH of various kinds of silica gel matrix with immobilized imidazole group in static conditions on sorption were measured. The sorption of cobalt in various conditions (pH, contact time of phases) with constant liquid-solid ratio (V/m = 50 ml/g) was studied. The distribution coefficients ranged between 200 and 50 000 ml/g (for imidazole), 85 and 120 ml/g (for DB18C6) and between 230 and 500 ml/g (for DA18C6) according to silica gel matrix used and according to the method of sorbent preparation. pH plays important role in the sorption of cobalt on prepared sorbents with immobilized crown ethers due to protonization of crown ethers. Protons significantly competes to sorption of cobalt in acidic solutions. The influence of presence of other heavy or toxic metals (Hg(II), Cd(II), Mn(II), Zn(II), Cu(II), Fe(III), Cr(III), Al(III) and the influence of sodium and potassium on sorption Co(II) from aqueous solutions was investigated. Sorption of cobalt decreases in order Hg > Cu > Cd > Zn, Fe > Mn > Al, Cr. The presence of sodium and potassium ions at concentration 0.05 mol/l significantly influences on the sorption of cobalt with sorbent with immobilized DB18C6 functional group.     

Kinetics, thermodynamic and chromatographic behaviour of the uranyl ions sorption from aqueous thiocyanate media onto polyurethane foams

The retention profile of uranyl ions from aqueous thiocyanate media by polyether-type based polyurethane foams (PUFs) has been studied to gain more information regarding the mechanism of extraction. The effect of pH, shaking time, surfactant type, extraction media, temperature and analyte concentration on the retention of uranyl ions onto PUFs has been studied. It has been found that, the sorption of uranyl ions involved in the formation of a ternary complex ion associate of uranyl ion, thiocyanate and PUFs is highly dependent on these parameters. The kinetics and thermodynamics of the uranyl ions sorption have been studied in more detail. The dependency of the extraction on the parameters can be explained via a “solvent extraction,” mechanism. However, owing to the complex nature of the PUFs a dual-mode sorption mechanism involving both absorptions related to “solvent extraction” and an added component for “surface adsorption” may be operated simultaneously. Attempts for quantitative retention and recovery of the uranyl ions in tap and industrial waste water samples by the proposed PUFs columns has been carried out and satisfactory results have been obtained. The cellular structure of the PUF sorbent offer unique advantages over a conventional bulk type sorbents in rapid, versatile effective separation and/or preconcentration of uranyl ions.