Removal of Zn(II) Ions from Aqueous Solution Using BPHA‐Impregnated Polyurethane Foam

Zn(II) ions sorption onto N‐Benzoyl‐N‐Phenylhydroxylamine (BPHA) impregnated polyurethane foam (PUF) has been studied extensively using radiotracer and batch techniques. Maximum sorption (～98%) of Zn(II) ions (8.9 × 10^?6 M) onto sorbent surface is achieved from a buffer of pH 8 solution in 30 minutes using 7.5 mg/mL of BPHA‐impregnated polyurethane foam at 283 K. The sorption data follow Langmuir, Freundlich and Dubinin‐Radushkevich (D‐R) isotherms. The Langmuir constants Q = 18.01 ± 0.38 μ mole g^?1 and b = (5.39 ± 0.98) × 10³ L mole^?1 have been computed. Freundlich constants 1/n = 0.29 ± 0.01 and C_m = 111.22 ± 12.3 μ mole g^?1 have been estimated. Sorption capacity 31.42 ± 1.62 μ mole g^?1, β = ?0.00269 ± 0.00012 kJ² mole^?2 and energy 13.34 ± 0.03 kJ mole^?1 have been evaluated using D‐R isotherm. The variation of sorption with temperature yields ΔH = ?77.7 ± 2.8 k J mole^?1, ΔS = ?237.7 ± 9.3 J mole^?1 K^?1 and ΔG = ?661.8 ± 117.5 k J mol^?1 at 298 K reflecting the exothermic and spontaneous nature of sorption. Cations like Fe(III), Ce(III), Al(III), Pb(II) and Hg(II) and anions, i.e., oxalate, EDTA and tartrate, reduce the sorption significantly, while iodide and thiocyanate enhanced the sorption of Zn(II) ions onto BPHA‐impregnated polyurethane foam.     

Partial separation of rhodium and iridium using polyurethane foam

Rhodium/III/ solutions react with tin/II/ chloride to form a short-lived yellow complex which is extracted by polyurethane foam. Iridium/IV/ solutions are decolourised by tin/II/ chloride but the metal is poorly extracted by foam. The rhodium/III/ complex is readily desorbed from foam using hydrochloric acid and acetone.     

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.     

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.     

Extraction of rhodium(III) by 1,3-diamyl-2-imidazolidinethione from hydrochloric acid solutions

The extraction of rhodium(III) with 1,3-diamyl-2-imidazolidinethione from hydrochloric acid solutions was studied. Optimum conditions for rhodium(III) extraction were determined. It was found that rhodium(III) was extracted from a 0.5 M solution of HCl at a phase contact time of 3 h by a coordination mechanism. The composition of the extracted compound was determined using electronic, ¹H and ¹³C NMR, and IR spectroscopy and elemental analysis. It was demonstrated that the extracting agent coordinated to the rhodium(III) ion through the sulfur atom.     

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.     

Retention profile of Fe,Mn and Cu onto chemically treated polyurethane with carbon disulfide

Dithiocarbamate modified polyurethane foam (DTC-PUF) was synthesized as a new solid-phase extraction sorbent for the preconcentration and determination of Fe(II), Mn(II) and Cu(II) in environmental samples using flame atomic absorption spectrometry. Maximum extraction of the elements was achieved at pH 5–7 and flow rate 3 mL min^?1. Quantitative desorption was achieved by 10 mL from 1.0 mol L^?1 HCl solution. The capacity of the sorbent was 149.2 ± 0.5, 237.5 ± 0.2, 200.2 ± 0.1 μg g^?1 and the limit of detection was of 0.015, 0.015 and 0.012 μg mL^?1for Fe(II), Mn(II) and Cu(II), respectively. A preconcentration factor of 100 was obtained for all elements. The developed method was successfully applied to the determination of the tested elements in water (tap and lake) and plant (spinach and parsley leaves) samples and showed good recovery values from 98 to 111% with corresponding RSD values ranged from 0.6 to 8.6%.     

Synergistic solvent extraction of copper, cobalt, rhodium and iridium into 1, 2-Dichloroethane at trace level by newly synthesized 25, 26, 27, 28-tetrahydroxy-5, 11, 17, 23-tetra-[4-(N-hydroxyl-3-phenylprop-2-enimidamido) phenylazo] calix[4]arene

A spectrophotometric method for determination of copper, cobalt, rhodium and iridium ions from nitric acid media after extraction of these ions by 25, 26, 27, 28-tetrahydroxy-5, 11, 17, 23-tetra-[4-(N-hydroxyl-3-phenylprop-2-enimidamido) phenylazo] calix [4] arene (THPAC) has been developed and possible synergistic effect has been investigated. The maximum enhancement was obtained in the presence of 30% 1, 2-dichloroethane in DMF and 3M nitric acid. The trace amounts of the metal were determined spectrophotometrically. Beer’s law was obeyed in concentration range 5.0–10.0 μg, 6.0–120.0 μg, 12.0–100.0 μg, and 10.0–130.0 μg/10 mL of the final solution of copper, cobalt, rhodium and iridium, respectively. The molar absorptivities (l mol^?1 cm^?1) and Sandell’s sensitivities (μg cm^?1) were calculated: Cu (II) = 0.96 × 10^4, 0.0066; Co (II) = 1.13 × 10⁴, 0.0052; Rh (III) = 0.98 × 10⁴, 0.012; and Ir (III) = 2.03 × 10⁴, 0.0095, respectively. Seven replicate analyses containing of 20.0 μg of Cu (II), 24.0 μg of Co (II), 36.0 μg of Rh (III) and 25.0 μg of Ir (III) gave mean absorbance 0.302, 0.462, 0.344, 0.264; and relative standard deviation 0.65, 0.85, 1.10, 1.08%, respectively. The interference of various ions was studied and optimum conditions were developed for determination of metals in certain alloys, environmental, pharmaceutical and synthetic samples.     

Determination of lead in water samples after its separation and preconcentration by 4,5-dihydroxy-1,3-benzenedisulfonic acid functionalised polyurethane foam

A new sorbent based on polyurethane foam functionalised with 4,5-dihydroxy-1,3-benzenedisulfonic acid (Tiron-PUF) was synthesised. This material was used in the development of a procedure for preconcentration of lead, with subsequent detection by flame atomic absorption spectrometry (FAAS). The influence of some variables involved in the extraction process was studied. Analytical parameters were evaluated using 50 and 500?mL of Pb (II) solution. Under optimum conditions, the system showed enrichment factors of 38 (50?mL) and 114 (500?mL). The detection limits obtained were 0.5 and 1.1?µg?L^?1 when volumes of 500 and 50?mL of Pb (II), respectively, were used. The method was applied to the determination of lead content in well water and drinking water samples collected in the town of Amelia Rodrigues, Bahia, Brazil.     

The Spectropolarimetric Back-Titration of Rhodium(III) with the Chiral Ligand (R,R)-(-)-Trans-1, 2-Cyclohexanediaminetetraacetic Acid

Abstract

Spectropolarimetric back-titrations are described for rhodium(III); the optically active ligand (R, R)-(-)-t?ans-l, 2-cyclohexanediaminetetraacetic acid (R, R(-)CDTA) is used as the complexing agent and cadmium(II) ion as the back-titrant. The optical rotation is monitored throughout the titration, and the optically active ligand and stereospecifically formed complexes serve as self-indicators. The end points are determined graphically by straight-line extrapolations from a plot of volume-corrected observed rotations versus ml of titrant. The rhodium(III) titration plots are representative of normal spectro-polarimetric back-titrations. The range of analyses of rhodium(III) was from 40–0.5 mg.     

Use of acetohydroxamic acid in the direct spectrophotometric determination of iron(III) and iron(II) by flow injection analysis

The direct spectrophotometric determination of iron(III) and iron(II) by flow injection analysis with acetohydroxamic acid and 1,10-phenanthroline as reagents is reported. The working ranges are 0.5–10 and 10–60 mg l^?1, respectively. Results obtained for synthetic mixtures of Fe(III) and Fe(II) and for acid extracts of haematite samples were accurate. Interference studies indicate that the method is highly selective.     

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.     

Flow-injection determination of europium after on-line reduction

A zinc reductor minicolumn is used in a flow-injection system for reduction of europium(III) to europium(II). Europium(II) is indirectly determined either spectrophotometrically by oxidation with iron(III) and reaction of the iron(II) formed with 1,10- phenanthroline, or spectrofluorimetrically by reaction with cerium(IV) and measurement of the cerium(III) produced. The reductor functions efficiently at flow rates up to 1 ml min^?1, which allows sample injection rates up to 100 h^?1. Linear calibration is achieved for 10–200 and 0.5–4 μg ml^?1 with detection limits of 2.5 and 0.25 μg ml^?1, by spectrophotometry and spectrofluorimetry, respectively.     

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..     

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.     

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

The extraction of cerium(III) from weakly acidic chloride solutions by HDEHP-nitrobenzene-loaded polyurethane foams could be analyzed quantitatively in terms of the equation: log(9.056 D_c)=log K_c+2.14 log (C_d?6C_c)+3 pH+log f_c where D_c is the distribution ratio of cerium(III) between the foam and aqueous phases, C_d and C_c are the total HDEHP and Ce(III) concentrations on the foam, respectively, log f_c=[Ce³⁺]_(sq)/[ΣCe(III)]_(aq), and K_c is the equilibrium constant of the equation: Ce _(aq) ³⁺ +2.14(HX)_2.8(o) ? ? CeX₆·H_3(o)+3H _(aq) ⁺ . Values of K_c under the different extraction conditions tested are given.     

Flow constant-current stripping analysis for antimony(III) and antimony(V) with gold fibre working electrodes : Application to Natural Waters

Antimony(III) is determined by means of electrolysis at ?0.40 V vs. Ag/AgCl on a gold-coated gold fibre electrode for 0.5–10 min in a redox buffer containing 0.01 M iron(II) in 0.10 M hydrochloric acid, and subsequent stripping with a constant current of 0.50μA either in 2 M hydrochloric acid or in 4 M hydrochloric acid/4 M calcium chloride. Antimony(V) is determined by the same procedure in 4 M hydrochloric acid medium. Bismuth(III) is masked by the addition of iodide to the sample prior to electrolysis. Antimony(III) and antimony(V) are determined by standard addition methods; the whole procedure including digital and graphical evaluation of the results is fully automated. The antimony(V) concentrations in the river water reference sample SLRS-1 and the seawater reference sample NASS-1 were found to be 0.63 and 0.31 μg l^?1 with standard deviations of 0.046 and 0.051 μg l^?1, respectively (n=15). The certified value for SLRS- 1 is 0.63±0.05 μg l^?1; no certified value is available for NASS-1.     

Enantioselective,Potentiometric Membrane Electrodes for the Determination of L‐Pipecolic Acid in Serum

L ‐Pipecolic acid is a marker for peroxisomal disorders. Three enantioselective, potentiometric membrane electrodes were designed for the enantioanalysis of L ‐pipecolic acid. These electrodes are based on carbon paste impregnated with different maltodextrins (DE: 4.0–7.0 (I), 13.0–17.0 (II) and 16.5–19.5 (III), respectively) as chiral selectors and they can be used reliably for enantiopurity assay of L ‐pipecolic acid using a potentiometric method in the concentration ranges of 10^?8–10^?3, 10^?8–10^?5 and 10^?10–10^?6 mol/L for the maltodextrins I, II and III, respectively, based electrodes, with very low detection limits (magnitude orders of 10^?9 for I and II, respectively and 10^?12 mol/L for III). The proposed electrodes can be successfully applied for the enantioanalysis of L ‐pipecolic acid in serum samples.     

Oxidation of organic substances with compounds of trivalent manganese: XXIII. Preparation,stability, and determination of the titer of standard solutions of the fluoride complex of trivalent manganese

A method of preparation of 10^?2 ?10^?3M standard solutions of the fluoride complex of manganese(III) by the reaction of manganese(II) with permanganate in a medium of potassium fluoride acidified with sulfuric acid has been developed. It has been found that in a medium of 1 M sulfuric acid, 0.5 M manganese(II) sulfate, and 0.1 M potassium fluoride these solutions are sufficiently stable for both direct and indirect titrimetric determinations. The titer was determined using potassium iodide as a primary standard and potentiometric, bipotentiometric, or biamperometric titration.     

Rhodium(III), palladium(II), and platinum(II) complexes with 2-(2-hydroxybenzoyl)-N-methylhydrazinecarbothioamide: Syntheses,structures, and spectral characteristics

The syntheses and spectral (IR, UV-VIS, XPS, and ¹H and ¹³C NMR) characteristics of the rhodium(III), palladium(II), and platinum(II) complexes with 2-(2-hydroxybenzoyl)-N-methylhydrazinecarbothioamide (HBMHCTA) are described. The coordination of HBMHCTA to the central metal ion and its intraligand rearrangement in the complex formation of rhodium(III) ions are studied. The structure of the mixed-ligand complex [Pd(H₂L)PPh₃] is determined by X-ray diffraction analysis.