Cyanex272 impregnated on Amberlite XAD-2 for separation and preconcentration of U(VI) from uranmicrolite (leachates) ore tailings

An organanophosphinic acid extractant Cyanex272 was impregnated on a macroporus polymeric solid support Amberlite XAD-2 and packed in a column to study sorption and desorption of U(VI) in HNO₃ media. Various physio-chemical parameters such as influence of HNO₃ concentration, amount of Cyanex272, nature of eluents, sample and eluent flow rates were studied systematically to optimize conditions for sorption and desorption of U(VI). The breakthrough volume for U(VI) was >1000 mL and column reusability was more than 50 cycles. U(VI) was selectively separated from some commonly associated rare earth elements and certain d-block elements in binary and synthetic mixtures. The method developed for U(VI) was applied for its recovery from uranmicrolite (leachate) ore tailings and an industrial effluent sample.     

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.     

Preconcentration and determination of ultra-trace amounts of U(VI) and Th(IV) using titan yellow-impregnated Amberlite XAD-7 resin

A simple and sensitive method for the determination of ultra trace amounts of U(VI) and Th(IV) ions by spectrophotometric method after solid-phase extraction on a new extractant-impregnated resin (EIR) has been reported. The new EIR was synthesised by impregnating a weakly polar polymeric adsorbent, Amberlite XAD-7, with titan yellow (TY) as extractant. The analytical method is based on the simultaneous adsorption of analyte ions in a mini-column packed with TY/XAD-7 and performing sequential elution with 0.5% (w/v) Na₂CO₃ for uranium and 2.0 M HCl for thorium. The influences of the analytical parameters including pH, salting out agent and sample volume were investigated. The interference effects of foreign ions on the retention of the analyte ions were also explored. The limits of detection for U(VI) and Th(IV) were as low as 50 and 25 ng L^?1, respectively. Relative standard deviations (n = 7) for U(VI) and Th(IV) were 3.1% and 2.9%, respectively. The method was successfully applied to the determination of ultra trace amounts of U(VI) and Th(IV) in different real matrices including industrial wastewater samples and environmental waters. The proposed method was validated using three certified reference materials and the results were in good agreement with the certified values.     

Extraction of U(VI) with Cyanex 302

U(VI) was quantitatively extracted from 1·10⁻³M HNO₃ using 5·10⁻³M Cyanex 302 in xylene and was stripped from organic phase with 5M HCl. The optimum extraction conditions have been evaluated by studying parameters like acidity, effect of diluents, extractant concentration and period of equilibration. Based on this data, the separations of uranium from binary and complex metal mixtures and its recovery from uranmicrolite tailings (leachate) were successfully tested. Uranium can be determined with a relative standard deviation of 0.4%.     

Sorption behaviour of lanthanum(III), neodymium(III), terbium(III), thorium(IV) and uranium(VI) on Amberlite XAD-4 resin functionalized with bicine ligands

The complexing properties (capacity, pH effect, breakthrough curve) of a chelating resin, containing bicine ligands, were investigated for La(III), Nd(III), Tb(III), Th(IV) and U(VI). Trace amounts of these metal ions were quantitatively retained on the resin and recovered by eluting with 1 M hydrochloric acid. The capacity of the resin for La(III), Nd(III), Tb(III), Th(IV) and U(VI) was found to be 0.35, 0.40, 0.42, 0.25 and 0.38 mmol g(-1), respectively. Separation of U(VI) and Th(IV) from Ni(II), Zn(II), Co(II) and Cu(II) in a synthetic solution was carried out.     

Sorption of U(VI) on granite

The sorption-desorption of uranium (VI) on Grimsel granite of Switzerland was studied under oxidizing conditions with an initial uranium concentration range of between 9.7·10^–7 and 4.5·10^–4M, using a batch technique. The sorption coefficients varied between 8.0 and 0.4 ml/g and sorption was not fully reversible. The data could be fitted to a Freundlich isotherm. By fitting the data with the Dubinin-Radushkevich equation, a mean energy of sorption of 10.7 kJ/mol was calculated, which corresponds to the energy of ion exchange reactions. The kinetic data could be interpreted by assuming diffusion into the crushed granite particles. The calculated pore diffusion coefficient was between 2.0·10^–11–7.7·10^–11 m²/s.     

Amberlite XAD-7 resin impregnated with 2-(1-(4-chlorophenyl)-4,5-diphenyl-1H-imidazol-2yl)-4-nitrophenol for enrichment of metal ions

The Amberlite XAD-7 resin modification was carried out by loading 2-(1-(4-chlorophenyl)-4,5-diphenyl-1H-imidazol-2yl)-4-nitrophenol (CPDPINP). Subsequently, this new sorbent was applied for the enrichment of metal ions such as Cu²⁺, Ni²⁺, Co²⁺ Zn²⁺ and Pb²⁺ ions. The effect of various parameters on their sorption and following recoveries was studied in column procedure. The preconcentrated ions were eluted by appropriate eluent and their contents were quantified by FAAS. This method has preconcentration factor of 150 and enrichment factor in the range of 20.8–29.1. At optimum values of all variables, the proposed method has linear calibration graphs in the range of 0.01 up to 0.29 μg mL⁻¹ with detection limit (3SDb/m, n = 15) between 1.6 and 2.6 ng mL⁻¹. This protocol is usable for successful analysis of Cu²⁺, Ni²⁺, Co²⁺ Zn²⁺ and Pb²⁺ ions in different matrices with reasonable recoveries (>93%) and acceptable relative standard deviation (<4.7%).     

Extraction of U(VI) by cyanex-272

Extraction of U(VI) from HNO₃, HCl and HClO₄ media using cyanex-272 (bis[2,4,4 trimethyl pentyl] phosphinic acid)/n-dodecane has been carried out. In the case of HNO₃ and HClO₄ media, the distribution ratio (D) value first decreases and then increases, whereas from HCl medium it first decreases and then remains constant with increase in H⁺ ion concentration. At lower acidities, U(VI) was extracted as UO₂(HA₂)₂ by an ion exchange mechanism, whereas at higher acidities as UO₂(NO₃)₂ ^.2(H₂A₂) following a solvation mechanism. The D for U(VI) by cyanex-272, PC-88A and DEHPA at low acidities follows the order cyanex-272 > PC-88A > DEHPA. Also, cyanex-272 was found to extract U(VI) more efficiently than TBP at 2M HNO₃. The effect of diluents on the extraction of U(VI) by cyanex-272 followed the order cyclohexane > n-dodecane > CCl₄ > benzene. The loading of U(VI) into cyanex-272/n-dodecane from 2M HNO₃ has shown that at saturation point, cyanex-272 was 78% loaded. No third phase was observed at the saturation level. The stripping of U(VI) from the loaded organic phase was not possible with water, it was poor with acetic acid and sodium acetate but quantitative with oxalic acid, ammonium carbonate and sodium carbonate.     

Selective extraction of U(VI), Th(IV), and La(III) from acidic matrix solutions and environmental samples using chemically modified Amberlite XAD-16 resin

A new grafted polymer has been developed by the chemical modification of Amberlite XAD-16 (AXAD-16) polymeric matrix with [(2-dihydroxyarsinoylphenylamino)methyl]phosphonic acid (AXAD-16-AsP). The modified polymer was characterized by a combination of ¹³C CPMAS and ³¹P solid-state NMR, Fourier transform-NIR-FIR-Raman spectroscopy, CHNPS elemental analysis, and thermogravimetric analysis (TGA). The distribution studies for the extraction of U(VI), Th(IV), and La(III) from acidic solutions were performed using an AXAD-16-AsP-packed chromatographic column. The influences of various physiochemical parameters on analyte recovery were optimized by both static and dynamic methods. Accordingly, even under high acidities (>4 M), good distribution ratio (D) values (10²–10⁴) were achieved for all the analytes. Metal ion desorption was effective using 1 mol L^–1 (NH₄)₂CO₃. From kinetic studies, a time duration of <15 min was sufficient for complete metal ion saturation of the resin phase. The maximum metal sorption capacities were found to be 0.25, 0.13, and 1.49 mmol g^–1 for U(VI); 0.47, 0.39, and 1.40 mmol g^–1 for Th(IV); and 1.44, 1.48, and 1.12 mmol g^–1 for La(III), in the presence of 2 mol L^–1 HNO₃, 2 mol L^–1 HCl, and under pH conditions, respectively. The analyte selectivity of the grafted polymer was tested in terms of interfering species tolerance studies. The system showed an enrichment factor of 365, 300, and 270 for U(VI), Th(IV), and La(III), and the limit of analyte detection was in the range of 18–23 ng mL^–1. The practical applicability of the polymer was tested with synthetic nuclear spent fuel and seawater mixtures, natural water, and geological samples. The RSD of the total analytical procedure was within 4.9%, thus confirming the reliability of the developed method.     

Preconcentration of copper, nickel and zinc with Amberlite XAD-16 resin

Summary An adsorption-elution and atomic absorption spectrophotometric method using Amberlite XAD-16 is proposed for the preconcentration and determination of Cu, Ni and Zn. Optimum conditions for the preconcentration were investigated. Recoveries of the elements were found to be 82.4±0.3%, 95±3% and 71±1% for Cu, Zn and Ni, respectively, at 95% confidence level. The recoveries were increased to about 99% for Cu and Ni by complexing with 1-(2-pyridylazo)-2-naphthol (PAN). The effect of Na and K on the preconcentration of trace metals has also been investigated. The method was applied to a tap water.     

Tri-n-octylamine impregnated Seplite LX-16 resin for extraction of U(VI) from sulfate medium

Journal of Radioanalytical and Nuclear Chemistry - Impregnation of tri-n-octylamine (TOA) into Siplite LX-16 resin, by two commonly used methods namely; wet and dry impregnation method, was studied...     

Adsorption characteristics of as(III) and as(V) with titanium dioxide loaded Amberlite XAD-7 resin.

The adsorption characteristics of As(V) and As(III) on titanium dioxide loaded Amberlite XAD-7 resin have been studied. The resin was prepared by impregnation of Ti(OC2H5)4 followed by hydrolysis with ammonium hydroxide. Batch adsorption experiments were carried out as a function of the pH, shaking time and the concentration of As(V) and As(III) ions. The resin showed a strong adsorption for As(V) from pH 1 to 5 and for As(III) from pH 5 to 10. The adsorption isotherm data for As(V) at pH 4 fitted well to a Langmuir equation with a binding constant of 59 dm3 mol(-1) and a capacity constant of 0.063 mmol g(-1). The data for As(III) at pH 7 also fitted well to a Langmuir equation with a binding constant of 5.4 dm3 mol(-1) and a capacity constant of 0.13 mmol g(-1). The effect of diverse ions on the adsorption of arsenic was also studied. Column adsorption experiments showed that the adsorption of As(III) is more favorable compared to As(V), due to both the faster adsorption and larger capacity for As(III) than As(V).     

Synergistic extraction of uranium(VI) and thorium(IV) with mixtures of Cyanex272 and other organophosphorus ligands

The extraction of thorium(IV) and uranium(VI) from nitric acid solutions has been studied using mixtures of bis(2,4,4-trimethylpentyl)phosphinic acid (Cyanex272 or HA), and synergistic extractants (S) such as tri-butylphosphate (TBP), tri-octylphosphine oxide (TOPO) or bis(2,4,4-trimethylpentyl)thiophosphinic acid (Cyanex301). The results showed that these metallic ions are extracted into kerosene as Th(OH)₂(NO₃)A·HA and UO₂(NO₃)A·HA with Cyanex272 alone. In the presence of neutral organophosphorus ligands TBP and TOPO, they are found to be extracted as Th(OH)₂(NO₃)A·HA·S and UO₂(NO₃)A·HA·S. On the other hand, Th(IV), U(VI) are extracted as Th(OH)₂(NO₃)A·HA·2S and UO₂(NO₃)A·HA·S in the presence of Cyanex301. The addition of neutral extractants such as TOPO and TBP to the extraction system enhanced the extraction efficiency of both elements while Cyanex301 as an acidic extractant has improved the selectivity between uranium and thorium. The effect of TOPO on the extraction was higher than other extractants. The equilibrium constants of above species have been estimated by non-linear regression method. The extraction amounts were determined and the results were compared with those of TBP. Also, it was found that the binding to the neutral ligands by the thorium–Cyanex272 complexes follows the neutral ligand basicity sequence.     

Geobacillus thermoleovorans immobilized on Amberlite XAD-4 resin as a biosorbent for solid phase extraction of uranium (VI) prior to its spectrophotometric determination

Geobacillus thermoleovorans subsp stromboliensis, was immobilized on an Amberlite XAD-4 ion exchanger and used as a solid phase extractant for the preconcentration of U(VI) ions prior to their determination by UV-VIS spectrophotometry. Parameters affecting the preconcentration (such as the pH value of the sample solution, the concentration of U(VI), the volume and type of eluent, the flow rate and the effect of potentially interfering ions) were studied. The optimum pH for the sorption of U(VI) was found to be pH 5.0. 5.0?mL of 1 M hydrochloric acid were used to eluate the U(VI) from the column. The loading capacity is 11?mg?g^?1. The limits of detection and quantification are 2.7 and 9.0?μg?L^?1, respectively, and relative standard deviations are <10?%. The method was applied to the determination of U(VI) in a certified reference sample (NCS ZC-73014; tea leaves) and in natural water samples.

Flow injection on-line spectrophotometric determination of thorium(IV) after preconcentration on XAD-4 resin impregnated with oxytetracycline

A very sensitive, selective and simple flow injection time-based method was developed for on-line preconcentration and determination of thorium(IV) at micro g L^–1 levels in environmental samples. The system operation was based on thorium(IV) ion retention at pH 4.0 in the minicolumn at a flow rate of 15.2 mL min^–1. The trapped complex was then eluted with 3.6 mol L^–1 HCl at a flow rate of 4.9 mL min^–1. The amount of thorium(IV) in the eluate was measured spectrophotometrically at 651 nm using arsenazo-III solution (0.05 % in 3.6 mol L^–1 HCl stabilized with 1 % triton X-100, 4.9 mL min^–1) as colorimetric reagent. All chemical, and flow injection variables were optimized for the quantitative preconcentration of metal and a study of interference level of various ions was also carried out. The system offered low backpressure and improved sensitivity and selectivity. At a preconcentration time of 60 s and a sample frequency of 40 h^–1, the enhancement factor was 97, the detection limit was 0.25 μg L^–1, and the precision expressed as relative standard deviation was 1.08 % (at 50 μg L^–1), whereas for 300 s of the preconcentration time and a sample frequency of 10 h^–1, the enhancement factor of 357, the detection limit (3σ) of 0.069 μg L^–1 and the precision of 1.32 % (at 10 μg L^–1) was reported. The accuracy of the developed method was sufficient and evaluated by the analysis of certified reference material IAEA-SL-1 (Lake Sediment) and spiked water samples.     

Separation and preconcentration of U(VI) on XAD-4 modified with 8-hydroxy quinoline

Amberlite XAD-4 adsorber resin was modified with 8-hydroxy quinoline (Oxine) by equilibrating with methanol solution of the reagent and the modified resin was used as a support material for the solid phase extraction and preconcentration of UO₂²⁺ from aqueous solution at pH between 4 and 5.5. Ten micrograms of uranium from 300 ml of aqueous phase could be quantitatively extracted in to 1 g of the modified resin giving an enrichment of 200. Uranium collected in the column could be eluted out with methanol-HCl mixture and determined spectrophotometrically using arsenazo(III) as the chromogenic reagent. The preconcentration could be made selective to uranium by using EDTA as a masking agent for transition metal ions and Th(IV).