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.     

Polyurethane foams as selective sorbents for noble metals : Quantitative extraction and separation of rhodium from iridium in hydrochloric acid containing tin(II) chloride

The distribution of rhodium(III) between polyether-type polyurethane foam and 0.5–5.0 mol dm^?3 hydrochloric acid in the presence of small amounts of tin(II) chloride is described. The distribution of rhodium is affected by the extraction temperature, acid concentration and the Sn(II):Rh ratio. The capacity of the polyurethane foam for rhodium is in excess of 0.5 mmol g^?1. Rhodium is presumably sorbed in the form of a chloro(trichlorostannato)rhodium(III/I) complex anion. Iridium is not extracted by the foam under corresponding conditions and can be separated quantitatively from rhodium.     

Separation of antimony(III) with iodide and dithizone by sorption on polyurethane foam from sulphuric acid medium for its spectrophotometric determination in glasses

A method for quantitative separation of antimony(III) by sorption on polyether based polyurethane foam and its spectrophotometric determination has been described. The method involves formation of a pink-red complex of antimony(III) with iodide (0.045M) and dithizone (2.3 x 10(-5)M) in 0.25-0.75M H(2)SO(4) medium, sorption of the complex on polyurethane foam (within 45 min) at room temperature followed by its elution with acidified acetone (acetone containing 0.008% H(2)SO(4)) and spectrophotometric measurement at 507.2 nm ( = 2.56 x 10(4) l mol cm). The method obeys Beer's law from 0.1 to 6.0 mug antimony(III). Tolerance limits of other ions are Co (100 mug), Ni (100 mug), Fe (10 mug), Cu (0.5 mug), Sn (20 mug), Zn (100 mug), As (100 mug), Mn (200 mug), Pb (50 mug), Ti (100 mug), V (50 mug), etc. Interference by iron and copper have been eliminated by treating with KOH prior to the extraction of antimony. The method has been standardized with glass samples spiked with known amounts of antimony and applied to the determination of antimony in various glasses.     

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.     

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.     

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..     

The separation of tellurium and selenium by polyurethane foam sorbents

Tellurium and selenium can be sorbed from hydrochloric acid and hydrobromic acid solution by both polyether and polyester-based polyurethane foam. Although some acid is needed, the substitution of sodium chloride or sodium bromide increases the extraction significantly. Tellurium is extracted rapidly with > 99% sorbed in 2 min from 1.0/5.0M and 2.0/4.0M hydrochloric acid/sodium bromide. Selenium can also be sorbed quantitatively but much more slowly so that a separation is possible based on the relative rates of extraction. The capacity of polyether foam is 3% by weight of tellurium.     

Modeling of iron adsorption on HTTA-loaded polyurethane foam using Freundlich,Langmuir and D-R isotherm expressions

The sorption of Fe(III) at low pH range from 1 to 4.5 on open cell polyether type HTTA-loaded polyurethane foam has been carried out using batch technique. The optimum shaking time for 2.5· 10^–4M solution of Fe(III) was found to be 30 minutes. The concept of macropore and micropore nature of polyurethane foam sorbent offers unique advantages of adsorption. Freundlich and Langmuir adsorption isotherms are followed at low concentration range from 1·10^–4 to 3·10^–4M solution of Fe(III). The Freundlich constant (1/n=0.46±0.013 andK=9.16±1.39 mg·g^–1) and Langmuir isotherm constants(M=21.78 mg·g^–1 andb=88.41±9.731·g^–1) were established. The sorption mean free energyE=12.22±0.09 kJ·mol^–1 and loading capacityC _m =145.21±6.1 mg·g^–1 were evaluated using Dubinin-Radushkevich isotherm, which suggested that the adsorption mechanism was chemisorption.     

Sorption of iron(III) in ionic and colloidal states on iron(III) oxide deposited on a silica gel sufrace

The sorption of iron(III) in ionic and colloidal states on iron(III) oxide deposited on a silica gel surface has been studied as a function of pH of aqueous solution by batch equilibrations. The behaviour of Fe³⁺ and colloidal Fe(III) on the sorbent column has also been investigated. Conditions for sorption of iron from aqueous solutions are given. The colloidal iron(III) can be quantitatively separated from Fe³⁺ on the sorbent column under given experimental conditions.     

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.     

Sorption-Photometric Determination of 1-Naphthol with Polyurethane Foams

Abstract

Two approaches to sorption-photometric determination of 1-naphthol in waters with application of polyurethane foams are offered. The first approach was based on sorption of a coloured 1-naphthol azoderivative, which was formed by the reaction with 4-nitrophenyldiazonium tetrafluoroborate (NFD). In the second variant, 1-naphthol is first sorbed by a polyurethane foam, and it is then transformed into a coloured azoderivative by sorbent treatment of a NFD solution. A coloured 1-naphthol azoderivative was determined immediately in the polyurethane foam using diffuse reflectance spectroscopy. Calibration graphs are linear in the interval of concentrations of 0.01 - 1 μg/ml. The analytical results indicated that a selective and sensitive analytical procedure could be easily applied to determination of 1-naphthol concentration in waters.     

Extraction of certain actinide and lathanide elements from different acidic media by polyurethane foams loaded with di-(2-ethylhexyl)phosphoric acid (HDEHP)

The partition of cerium(III) between aqueous acid perchlorate solutions and polyurethane foams loaded with solutions of di-(2-ethylhexyl)phosphoric acid (HDEHP) in nitrobenzene has been investigated and the apparent polymerization number of HDEHP on the foam has been determined. The mechanism of extraction is discussed in the light of the results. It has been found that Ce(III) is generally extracted on the foam by a cation exchange mechanism.     

Adsorption syntax of Au(III) on unloaded polyurethane foam

The nature of adsorption behavior of Au(III) on polyurethane (PUR) foam was studied in 0.2M HCl aqueous solution. The effect of shaking time and amount of adsorbent were optimized for 3.16·10⁻⁵M solution of Au(III) in 0.2M HCl. The classical Freundlich and Langmuir adsorption isotherms have been employed successfully. The Freundlich parameters 1/n and adsorption capacityK are 0.488±0.016 and (1.40±0.22)·10⁻² mol·g⁻¹, respectively. The Langmuir constants of saturation capacityM and binding energyb are (1.66±0.08)·10⁻⁴mol·g⁻¹ and 40294±2947 l·g⁻¹, respectively, indicating the monolayer chemical sorption. The mean free energy (E) of adsorption of Au(III) on PUR foam has been evaluated using D-R isotherm and found to be 11.5±0.16 kJ·mol⁻¹ reflecting the ion exchange type of chemical adsorption. The effect of temperature on the adsorption has also been studied. the isosteric heat of adsorption was found to be 44.03±1.66 kJ·mol⁻¹. The thermodynamic parameters of ΔG, ΔH, ΔS and equilibrium constantK _c have been calculated. The negative values of ΔG, ΔH and ΔS support that the adsorption of Au(III) on PUR foam is spontaneous, exothermic and of ion exchange chemisorption. The nature of the Au(III) species sorbed on PUR foam have been discussed.     

Determination of Hg from Cu concentrates by X-ray fluorescence through preconcentration on polyurethane foam

A methodology was developed for the separation and determination of microamounts of mercury from copper concentrate samples by wavelength dispersive X-ray fluorescence (WDXRF) after solid-phase extraction of mercury from iodide medium using polyurethane foam (PUF). The best sorption conditions for the Hg-KI-PUF system were settled using X-ray fluorescence technique after collection of ground PUF on a filter paper by vacuum filtration and direct measurement of the intensity signal of the sorbed mercury on PUF. The main parameters of sorption such as iodide concentration, pH, shaking time and sample dilution effect were studied. The system shows rapid kinetic sorption and maximum X-ray intensity signal was achieved after shaking for 2 min a 0.01 mol l⁻¹ iodide solution containing microamounts of mercury in the pH range from 1.0 to 9.0. Effective sorption up to a volume of 0.9 l allows preconcentration of mercury. A linear fit up to 50 μg mercury was obtained by the plot of the initial mercury mass in the bulk solution (0.5 l) vs. its respective XRF intensity signal measurement on ground PUF after the sorption process. The calibration sensitivity, quantification and detection limits found were 9.09 CPS μg⁻¹, 9.0 and 2.7 μg, respectively. The sorption of many elements was also evaluated under the best conditions. High concentrations of Cu(II) and Fe(III) interfere seriously. Mercury-selective separation could be achieved using citrate or EDTA as masking agent; no interference due to copper matrix samples was observed in citrate medium. This methodology was evaluated by recovery for mercury determination in copper concentrate ore samples supplied by a mining industry and copper sulfate salts; the results were between 98% and 106%.     

SORPTION BEHAVIOR AND MECHANISM OF SAMARIUM(III) ON AMINO METHYLENE PHOSPHONIC ACID RESIN

Sm(III) was quantitatively adsorbed by amino methylene phasphonic acid resin (APAR)in the medium of pH=5.0. The statically saturated sorption capacity is 251mg/g @ resin. Sm(III)adsorbed on APAR can be reductively eluted by 2.0mol/L HCl. The sorption rate constant is k2gs=1.35 ×1O-Ss-1. The sorption behavior of APAR for Sm(I) obeys the Freundlich isotherm. The enthalpy change △H° of sorption is 24.9k J/mol. The apparent activation energy is Ea= ll. 7kJ/mol.The sorption mechanism shows that the nitrogen and oxygen atoms of the functional group of APAR coordinated with Sm(Ⅲ) to form coordination bond.     

Kinetics of radioeuropium sorption on Gorleben sand from aqueous solutions and ground water

Kinetics of Eu sorption on sandy sediment from Gorleben, Germany, containing humic substances, was studied by radiotracer method in batch experiments at very low europium concentration (3.4^.10^-8 mol/l), with the aim to find kinetic parameters suitable for modeling Eu migration in bed of the sediment and to elucidate the mechanism of the sorption. Experiments were evaluated using a new simplified method taking into account simultaneous sorption/desorption of Eu on the walls of sorption vessel. Five kinetic functions were tested, of which that describing diffusion in inert surface layer of sorbent proved most suitable. The effects of pH (3.0-8.8) by addition of Aldrich humic acid (10 mg/l), addition of hydrogencarbonates (5^.10^-3 mol/l) and preequilibration of the sediment with solution or of Eu with solution were examined. From the results it has been concluded that the kinetics and mechanism of the sorption strongly depend on pH. At pH 4.8 Eu is sorbed mainly as humate complex from the solution of humic acid. The addition of humic acid accelerates the sorption. Carbonate complexes of Eu are the probable forms sorbed at pH 8.8. The presence of humic substances in the slightly alkaline solutions suppresses the rate of the sorption due to slow dissociation of Eu-humate complexes.     

Sorption of chromium(VI) and chromium(III) on aluminium hydroxide

Factors that influence the sorption of Cr(VI) and Cr(III) on aluminium hydroxide were investigated. The sorption of chromates decreases as the pH of the suspension increases. The mechanism of CrO ₄ ^2– sorption was interpreted in terms of reactions between chromates and –OH and/or H₂O groups at the hydroxide/liquid interface. It has been shown that chromates are more tightly sorbed on aluminium hydroxide compared to other anions, e.g. chlorides. On the other hand, specifically absorbed anions, such as molybdates, compete strongly with chromates for the sorption sites. The sorption of chromium(III) increases with the pH of the suspension. Also, the sorption of chromium(III) is suppressed in the presence of citrate ions. The best conditions for the fixation of Cr(VI) and Cr(III) by aluminium hydroxide are presented.     

Reversed phase foam chromatography : Separation of iron from copper,cobalt and nickel in the tri-n-butyl phosphate-hydrochloric acid system

The separation of iron from cobalt, copper and nickel by reversed-phase foam chromatography was investigated. The distribution of Fe, Co and Cu in TBP-HCl and TBP(polyurethane foam)-HCl systems was measured. Iron can be separated from the three other metals on polyether-type polyurethane foam columns loaded with TBP. The break-through curve of iron on TBP (polyurethane foam) columns was measured. The column was found suitable for the separation of ⁵⁸Co and ⁵⁹Fe isotopes.     

Separation of titanium, iron and aluminium on a chelating resin with benzoylphenylhydroxylamine group and application to bauxite and clay

Summary A chelating polystyrene based resin containing N-benzoyl-N-phenylhydroxylamine has been sythesized by two methods and characterized. Conditions for quantitative separation of Ti(IV), Fe(III) and Al(III) on the resin have been studied. A method has been developed for the determination of these three metal ions in bauxite or clay samples after their separation on the resin with recoveries of 98.5–99.5% for different metal ions. The maximum sorption values are observed at pH 1, 2.5 and 2.5 for Ti(IV), Fe(III) and Al(III), respectively, which are recovered by successive elution with 1 mol/l H₂SO₄, 2 mol/l HCl and 4 mol/l H₂SO₄ in the above order.