Reversed-phase foam chromatography: Separation of trace amounts of cobalt from nickel in the tri-n-octvlamine-hydrochloric acid system

The separation of cobalt and nickel in hydrochloric acid media by reversed-phase chromatography on open-cell polyether-type polyurethane foam columns loaded with tri-n-octylamine hydrochloride has been studied. The results showed that good results are obtained with 11.4 and 17.7% loadings of the amine. The separation was studied in the Ni:Co range from 1 to 10⁸.     

Polyurethane-pyridylazonaphthol foams in the preconcentration and separation of trace elements

The feasibility of using PAN—polyether and polyester polyurethane foams in batch and column operations has been examined. The effects of pH, plasticizer and various anions present in the aqueous solution on the extraction behaviour of cobalt, iron and manganese have been investigated. In dynamic systems, the effect of flow rate on the extraction efficiencies of these metal ions has been investigated. The uptake of cobalt(III) and manganese(II) on PAN—polyester foam columns is quantitative at flow rates up to 10 ml min^-1 and 2 ml min^-1, respectively. The retention of iron(III) by the foam column is not quantitative even at a flow rate of 1 ml min^-1. Preconcentration of cobalt and its separation from various concentrations of manganese are successful..     

Studies in the complex formation of metal ions with sugars. I. The complex formation of cobalt(II), cobalt(3), copper(II) and nickel(II) with mannitol

The use of elastic polyurethane foam as a support for chloranil was proved successful. Reductions of cerium(IV), vanadium(V) and iron(II) on foam-filled columns were carried out quantitatively and rapidly. The effect of flow-rate and temperature on the reduction of each metal ion was examined in detail. Cerium(IV) was reduced quantitatively on passing through the foam-redox column at flow-rates of 2–11 ml min^-1 at room temperature. The reduction of vanadium(V) and iron(III) was slower; complete reduction occurred only at flow-rates up to 4 and 2 ml min^-1 for V(V) and Fe(III), respectively. At 35°, however, it was possible to use flow-rates of 7 and 6 ml min^-1 for the quantitative reduction of V(V) and Fe(III), respectively.     

Molybdenum determination in iron matrices by ICP-AES after separation and preconcentration using polyurethane foam

A procedure is proposed for the separation and determination of molybdenum in iron matrices by a batch process. It is based on the solid-phase extraction of the molybdenum(V) ion as thiocyanate complex on polyurethane (PU) foam. The extraction parameters were optimized. Using 0.20 mol L^–1 hydrochloric acid, a thiocyanate concentration of 0.10 mol L^–1, 100 mg of polyurethane foam and shaking time of 10 min, molybdenum (5–400 μg) can be separated and preconcentrated from large amounts of iron (10 mg). Desorption was carried out instantaneously by conc. nitric acid or acetone. Distribution coefficients, sorption capacity of the PU foam and coefficients of variation were also evaluated. The effect of some ions on the separation procedure was assessed. Iron(III) should be reduced to iron(II). The proposed procedure was used to determine molybdenum in standard iron matrices such as steel and pure iron. The achieved results did not show significant differences with certified values.     

Separation and determination of some trivalent metal ions using rhodamine B grafted polyurethane foam

The incorporation of rhodamine B into polyurethane foam matrix was prepared by mixing the rhodamine B with polyol (polyether) prior to the addition of diisocyanate reagent to form the polyurethane foam material. Rhodamine B grafted polyurethane foam (Rod.B-PUF) was found to be very suitable for the separation and preconcentration of trivalent metal ions e.g. bismuth (III), antimony (III) and iron (III) from thiocyanate solutions. Bismuth and antimony were separated from concentrated acid medium (1–6 M H₂SO₄). Iron (III) was separated from pH 1 to 3. The kinetics of sorption of the Bi (III), Sb (III) and Fe (III) onto the Rod.B-PUF was found to be fast, the extraction is accomplished from 5 to 10 min with average values of half-life of sorption (t_1/2) of 2.9 min. The average values of the Gibbs free energy (ΔG) for the sorption of metal ions onto Rod.B-PUF are ?6.6 kJ mol^?1, which reflect the spontaneous nature of sorption process. The sorption mechanism of the metal ion onto Rod.B-PUF was also discussed.     

Insight of solvent extraction process: Reassessment of trace level determinations

Solvent extraction is hoary yet modern technique with great scope of research due to the various intriguing phenomena in the system. Tri-n-butyl phosphate (TBP) is a well known extractant which has been extensively used for separation of uranium matrix prior to elemental profiling. In this paper, one of the impurities namely Fe is being considered as it posed a challenge to the separation due to its co-extraction with TBP along with uranium. In these studies, for the first time, the existence of cation-cation inner sphere complexes between the UO₂²⁺and Fe³⁺ ions in both aqueous and organic phases have been establisted in addition to the selective separation of iron from uranium sample matrix using only TBP. The data from both spectrophotometric and thermophysical studies corroborated one another confirming the presence of cation-cation interactions (CCIs). The developed solvent extraction with only TBP showed almost no interferences on the iron extraction from matrix uranium and other co-ions like aluminum and copper. This has been the first time application of pure TBP for selective removal of iron from uranium samples. The procedure possessed excellent reproducibility and robustness.     

Reversed-phase foam chromatography : Chemical enrichment and separation of gold in the tributylphosphate-thiourea-perchloric acid system

Gold(III) is quantitatively extracted from acidic solution of thiourea into tri-n-butyl phosphate (TBP). The extracted species contains one molecule of thiourea and four molecules of TBP for each atom of gold. On short columns of TBP-loaded polyurethane foam, gold(III) can be separated from many other elements by retention from 0.1 M perchloric acid solution containing 3% thiourea and 1% sodium perchlorate. Flow-rates of 50–60 ml min^?1 are possible. Trace amounts of gold can be separated quantitatively from high concentrations of Zn²⁺, Co²⁺, Ni²⁺, Fe³⁺, Sb³⁺, Cu²⁺, Bi³⁺ and Pd²⁺, which have a negligible effect on the rate of adsorption of the gold-thiourea complex. The chemical enrichment of gold from dilute aqueous solutions is also possible.     

An experimental study on high-purity uranium refining by passing in succession through pulsed extraction,washing, and stripping columns

Nuclear-purity uranium was refined by passing a solution of uranyl nitrate in 3–5 M HNO₃ in succession through pulsed extraction, washing, and stripping columns for feeding into the U(III)–U(IV) chemical exchange system for uranium isotope separation. The extractant (tri-n-butyl phosphate, TBP), the diluent (kerosene), nitric acid, ammonium carbonate, sodium nitrate, and water were preliminarily refined to chemical purity. The diameter and height of pulsed columns for uranium purification was 25 and 1500 mm, respectively, and the pulse frequency was 1 s^–1. The content of transition metals (Fe, Co, Ni, Cu, Ag) and Pb, which can catalyze the U(III) oxidation in acidic aqueous solutions, was reduced to the level lower than 1 ppm (10^–4%). The total purification factor was higher than 103. The purification required 3–4 theoretical plates with HETP of the columns of 35–40 cm.     

Spectrophotometric determination of traces of iron after extraction of Fe(II)-phenanthroline complex on polyurethane foam

A spectrophotometric method for the determination of traces of iron in glass and ceramic materials has been developed. The method involves formation of the Fe(II)-phenanthroline complex at pH 3-4 in aqueous medium, followed by its selective extraction and preconcentration on polyurethane foam from 2.5M perchloric acid and finally elution of the complex with acetone for spectrophotometric measurement at 510 nm. A wide linearity range from 0.05 to 3 mu g/ml Fe is obtained with the method. Co, Cu and Ni have no significant effect when they are present in the weight ratios Fe:Co < 1:2, Fe: Cu < 1:10 and Fe: Ni < 1:50. The method yielded satisfactory results when applied to various glass and ceramic samples.     

Extraction studies on iron

The extraction of Fe(III) and Fe(II) from various aqueous acidic solutions, with nitrobenzene, Amberlite LA-2, TBP and HDEHP is described. Conditions are given for the separation of Fe(III) from Fe(II). The extraction and separation of Fe(III) and Fe(II) is most adequate from HCl solutions, using the four solvents. The extraction of iron halides from H₂SO₄ solutions has been studied. The effect of water-miscible alcohols on the distribution of Fe(III) and Fe(II) was also studied. Extraction equilibria and mechanisms were proposed on the basis of the obtained results.     

Formation cross section of iron-60 with reactor neutrons in59Fe(n, γ)60Fe reaction

Ingrowth of⁶⁰Co radioactivity in an iron sample irradiated in a nuclear reactor has been measured for determination of formation cross section of⁶⁰Fe in the⁵⁹Fe(n, )⁶⁰Fe reaction with reactor neutrons. After 5 years cooling, the irradiated iron was purified from⁶⁰Co and other radioactive nuclides by an anion exchange separation method and isopropyl ether extraction in hydrochloric acid. The amount of⁶⁰Co ingrowth was measured by -spectrometry using a Ge-detector coupled to a multichannel pulse height analyzer 4 years after the purification of iron. Neutron flux of the irradiation position was calculated from the amount of⁵⁵Fe produced. The observed value of 12.5±2.8 barn is slightly greater than reported value for burnup cross section of⁵⁹Fe(n, x)X, where x refers , , d, p and 2n, and X is any nuclide produced by the above reactions.     

Anionenaustauschtrennungen der mit Tributylphosphat extrahierbaren Elemente. I

Zusammenfassung Das Verhalten von U(VI) und Fe(III) am stark basischen Anionenaustauscher Dowex 1, X8 (Chloridform) in TBP-haltigen salzsauren Lösungsmittelgemischen wurde systematisch untersucht. Daraus konnten zwei verschiedene Methoden zur Trennung der genannten Elemente auf Ionenaustauschersäulen entwickelt werden, wobei durch Kombination von Extraktion und Ionenaustausch eine Abtrennung des Eisens und des Urans auch von anderen Elementen möglich war.Die Trennungen erfolgten in Medien folgender Zusammensetzung: 30 Vol.% TBP, 60 Vol.% Methylglykol und 10 Vol.% 12-m Salzsäure sowie 40 Vol.% TBP-Kerosin (50 vol.%ig) und 60 Vol.% einer Aceton-Salzsäuremischung (95 Vol.% Aceton und 5 Vol.% 12-m Salzsäure).Weiters wurde eine Methode zur spektrophotometrischen Bestimmung von Eisen(III) in einem TBP-haltigen Lösungsmittelgemisch entwickelt.

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Anion exchange separations of the elements that may be extracted with tributyl phosphate. I

Summary A systematic study was made of the behavior of U(VI) and Fe(III) on strongly basic anion exchanger Dowex 1, X8 (chloride form) in hydrochloric acid solvent mixtures containing TBP. The findings led to two different methods for the separation of the named elements on ion exchange columns, whereby by a combination of extraction and ion exchange it was possible to achieve a separation of the iron and the uranium also from other elements.The separations took place in media of the following composition: 30 volume% TBP, 60 volume% methylglycol and 10 volume% of 12 M hydrochloric acid as well as 40 volume% TBP-kerosene (50 volume%) and 60 volume% of an acetone-hydrochloric acid mixture (95 volume% acetone and 5 volume% 12 M hydrochloric acid). Furthermore a method was developed for the spectrophotometric determination of iron(III) in a solvent mixture containing TBP.

     

Preconcentration and separation of some organic water pollutants with polyurethane foam and activated carbon

Summary Although pesticides and phenols, cause reproductive failure in many areas of the world, there is a no effective means of treating waste water containing these compounds. This work deals with the adsorption of insecticides and phenols from aqueous solution by untreated porous polyurethane foam and activated carbon. Static experiments showed that in comparison with activated carbon a reasonable percentage of the compounds was adsorbed by the foam. Attempts were therefore made to extract these species from aqueous solution by foam column chromatography.The results showed that the adsorption of the compounds was brought about by a mechanism similar to that of solvent extraction. The effect of various experimental conditions such as temperature, extracting medium, pH, contact time, volume of sample flow rate, compound concentration, and eluting solvents on the retention and separation of the compounds has been determined. The height equivalent to a theoretical plate (HETP) was calculated from breakthrough capacity curves and from chromatograms obtained from polyurethane foam columns for the insecticide Dyfonate; values were in the range 2.1–2.3 mm at 10–15 ml min^–1. Extraction of the compounds from natural water, and subsequent recovery, were both found to be complete. The high capacity of polyurethane provides advantages over activated carbon; in particular, large sample volumes can be analyzed at high flow rates.     

Co-crystallization of ultramicro quantities of cobalt with α-nitroso-β-naphthol

The co-crystallization of ultramicro quantities of cobalt with α-nitroso-β-naphthol, was investigated by radio-tracer techniques. More than 99% cobalt, even when carrier-free, could be recovered. The distribution was studied and appeared to follow the logarithmic distribution law. The interference of a large excess of zinc was almost negligible. The method was applied to tlie carrier-free separation of cobalt isotopes (⁵⁵Co, ⁵⁶Co, ⁵⁷Co, ⁵⁸Co) produced by deuteron bombardment of an iron target. Contamination by manganese (⁵⁴Mn, ⁵²Mn) and iron (⁵⁹Fe) was, even in the absence of manganese carrier, almost negligible.     

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.     

Removal of organic pollutants from aqueous solution. V. Comparative study of the extraction, recovery and chromatographic separation of some organic insecticides using unloaded polyurethane foam columns

The concentration of dissolved insecticides in aqueous media was determined by chromatographic separation on polyurethane foam columns. The results of preliminary screening tests on the removal of insecticides by the unloaded polyurethane foam indicated that a reasonable percentage of the insecticides was retained on the foam. Therefore attempts were made to extract these compounds from aqueous media using foam columns. Various parameters affecting the retention and separation of these compounds were studied, including temperature, flow-rate, pH, insecticide concentration, shaking time, sample volume and eluting solvent. The complete separation and quantitative recovery of these compounds from the foam with acetone in a Soxhlet extractor were achieved. The method can be used to preconcentrate insecticides in tap water and modified to determine dissolved insecticides in industrial and natural waters. Polyurethane foam has a good capacity for use when large volume samples need to be handled and is an inexpensive sorbent compared to other known solid sorbents.     

A Versatile Iron–Tannin‐Framework Ink Coating Strategy to Fabricate Biomass‐Derived Iron Carbide/Fe‐N‐Carbon Catalysts for Efficient Oxygen Reduction

The conversion of biomass into valuable carbon composites as efficient non‐precious metal oxygen‐reduction electrocatalysts is attractive for the development of commercially viable polymer electrolyte membrane fuel‐cell technology. Herein, a versatile iron–tannin‐framework ink coating strategy is developed to fabricate cellulose‐derived Fe₃C/Fe‐N‐C catalysts using commercial filter paper, tissue, or cotton as a carbon source, an iron–tannin framework as an iron source, and dicyandiamide as a nitrogen source. The oxygen reduction performance of the resultant Fe₃C/Fe‐N‐C catalysts shows a high onset potential (i.e. 0.98 V vs the reversible hydrogen electrode (RHE)), and large kinetic current density normalized to both geometric electrode area and mass of catalysts (6.4 mA cm^?2 and 32 mA mg^?1 at 0.80 V vs RHE) in alkaline condition. This method can even be used to prepare efficient catalysts using waste carbon sources, such as used polyurethane foam.     

简易电沉积法制备CoFe-P催化剂用于高效析氧反应

开发低成本、高活性且稳定的非贵金属催化剂是实现大规模电解水制氢的关键所在。在此,我们通过简便、合理的电沉积法在泡沫镍(NF)上构建了一种具备超薄二维纳米片形貌的高度非晶相Co1Fe1-P薄膜用于高效催化析氧反应（OER）。在1.0mol·L^-1 KOH溶液中,所制备的Co1Fe1-P/NF催化剂在电流密度为10和100 mA·cm^-2处的过电位分别为274.4和329.5 mV,Tafel斜率仅为45.3 mV·dec^-1,可以媲美商业RuO₂催化剂。此外,Co1Fe1-P/NF催化剂在10 mA·cm^-2的100 h计时电压法测试和1 000次循环伏安法测试中均表现出卓越的催化稳定性。Co1Fe1-P/NF催化剂优秀的催化活性归因于其独特的形貌、高度非晶相结构提供的低能垒、优化的电子结构以及钴磷化物和铁磷化物的强协同效应。     

简易电沉积法制备CoFe-P催化剂用于高效析氧反应

开发低成本、高活性且稳定的非贵金属催化剂是实现大规模电解水制氢的关键所在。在此,我们通过简便、合理的电沉积法在泡沫镍(NF)上构建了一种具备超薄二维纳米片形貌的高度非晶相Co1Fe1-P薄膜用于高效催化析氧反应(OER)。在1.0mol·L^-1 KOH溶液中,所制备的Co1Fe1-P/NF催化剂在电流密度为10和100 mA·cm^-2处的过电位分别为274.4和329.5 mV,Tafel斜率仅为 45.3 mV·dec^-1,可以媲美商业 RuO₂催化剂。此外,Co1Fe1-P/NF 催化剂在 10 mA·cm^-2的 100 h 计时电压法测试和1 000次循环伏安法测试中均表现出卓越的催化稳定性。Co1Fe1-P/NF催化剂优秀的催化活性归因于其独特的形貌、高度非晶相结构提供的低能垒、优化的电子结构以及钴磷化物和铁磷化物的强协同效应。     

Molybdenum determination in iron matrices by ICP-AES after separation and preconcentration using polyurethane foam

A procedure is proposed for the separation and determination of molybdenum in iron matrices by a batch process. It is based on the solid-phase extraction of the molybdenum(V) ion as thiocyanate complex on polyurethane (PU) foam. The extraction parameters were optimized. Using 0.20 mol L-1 hydrochloric acid, a thiocyanate concentration of 0.10 mol L-1, 100 mg of polyurethane foam and shaking time of 10 min, molybdenum (5-400 micrograms) can be separated and preconcentrated from large amounts of iron (10 mg). Desorption was carried out instantaneously by conc. nitric acid or acetone. Distribution coefficients, sorption capacity of the PU foam and coefficients of variation were also evaluated. The effect of some ions on the separation procedure was assessed. Iron(III) should be reduced to iron(II). The proposed procedure was used to determine molybdenum in standard iron matrices such as steel and pure iron. The achieved results did not show significant differences with certified values.