Retention profile, kinetics and sequential determination of selenium(IV) and (VI) employing 4,4'-dichlorodithizone immobilized-polyurethane foams

Polyurethane foams (PUFs) loaded with the chromogenic reagent 4,4′-dichlorodithizone (Cl₂H₂D_Z) have been investigated for the quantitative retention, chemical speciation and sequential determination of traces of inorganic selenium(IV) and (VI) from aqueous media containing bromide ions. The retention profile of selenium(IV) onto the reagent loaded foam followed a dual-mode sorption mechanism involving both absorption related to “solvent extraction” and an added component for surface adsorption. The kinetics and thermodynamic characteristics of selenium(IV) uptake onto PUFs have been studied. The kinetics of selenium(IV) sorption onto PUFs was found fast, reached equilibrium in few minutes and followed a first-order rate constant in presence of bromide ions in the extraction media. The thermodynamic parameters, ΔH, ΔS and ΔG, indicated the exothermic and spontaneous nature of the sorption process. The sorption and the recovery percentages of inorganic selenium(IV) from fresh water by the proposed loaded foam columns were achieved quantitatively. The height equivalent to theoretical plate (HETP), the number of layers (N), breakthrough capacity and the critical capacity for selenium(IV) uptake onto Cl₂H₂D_Z loaded foams columns were found to be 1.3, 103, 8.6 and 7.2 mg/g, respectively. The method was successfully applied for the chemical speciation and sequential determination of inorganic selenium(IV) and/or (VI) species spiked to fresh and industrial wastewaters.     

Dual-wavelength β-correction spectrophotometric determination of trace concentrations of cyanide ions based on the nucleophilic addition of cyanide to imine group of the new reagent 4-hydroxy-3-(2-oxoindolin-3-ylideneamino)-2-thioxo-2H-1,3-thiazin-6(3H)-one

A simple, fast, low cost and sensitive direct β-correction spectrophotometric assay of cyanide ions based on its reaction with the reagent 4-hydroxy-3-(2-oxoindolin-3-ylideneamino)-2-thioxo-2H-1,3-thiazin-6(3H)-one, abbreviated as HOTT in aqueous media of pH 7-10 is described. The electronic spectrum of the produced brown-red colored species showed well defined and sharp peak at λ_max = 466 nm. The effective molar absorptivity for the produced cyano compound was 2.5 × 10⁴ L mol⁻¹ cm⁻¹. Beer's law and Ringbom's plots were obeyed in the concentration range 0.05-2.0 and 0.30-1.5 μg mL⁻¹ cyanide ions, respectively. The proposed method offers 16.0 and 50.3 μg L⁻¹ lower limits of detection (LOD) and quantification (LOQ) of the cyanide ion, respectively. The analytical utility of the method for the analysis of cyanide ions in tap and drinking water samples was demonstrated and the results were compared successfully with the conventional cyanide ion selective electrode. The short time response and the detection by the naked eye make the method available for the detection and quantitative determination of cyanide in a variety of samples e.g. fresh and drinking water. Moreover, the structure of the produced colored species was determined with the aid of spectroscopic measurements (UV-Vis, IR, ¹H and ¹³C NMR) and elemental analysis.     

Iodometric microgram determination of Mn(II) in aqueous media by an indirect chemical amplification reaction

A rapid, simple and highly sensitive iodometric amplification method is described for the determination of microgram amounts of Mn(II). The method is based on oxidation of Mn(II) with an excess of periodate in acetate buffer (pH 2.8-3.0), masking of the unreacted periodate with molybdate, and after addition of iodide, titration of the liberated iodine is with thiosulphate. The proposed method offers 20-fold amplification for Mn(II) and was found suitable for the determination of Mn(II) in the presence of permanganate ions. Mn(II) in tap water and an industrial waste water has been successfully determined by the proposed method.     

Synthesis,Physicochemical and Thermal Analyses of Ru(III), Pt(IV), and Ir(III) Complexes with NO Bidentate Schiff Base Ligand

Russian Journal of Physical Chemistry A - The chemical reaction of the 2-[(2,3-dihydroxybenzylidene)amino]benzoic acid (H3L2) Schiff base ligand with Ru(III), Pt(IV) and Ir(III) transition metal...     

Retention profile and subsequent chemical speciation of chromium (III) and (VI)) in industrial wastewater samples employing some onium cations loaded polyurethane foams

The retention of chromium (VI) from aqueous media onto tetraphenylarsonium chloride (TPAs⁺Cl⁻) or tetraphenylphosphonium bromide (TPP⁺Br⁻) immobilized polyurethane foams (PUFs) was fast and followed first order reaction. The kinetic data of the retention step were subjected to Weber-Morris, Lagergren, Bhattacharya and Venkobachar and Bt kinetic models. The results revealed that, film and intraparticle transport might be the two steps controlling the rate of chromium (VI) sorption from the aqueous acid solutions of pH ∼ zero. The positive values of the Δ H of chromium (VI) retention by the reagents loaded PUFs were interpreted as an endothermic process. Under the optimum pH (pH ∼ zero ) of the aqueous solution, the proposed TPAs⁺Cl⁻ or TPP⁺Br⁻ immobilized PUFs was successfully used in a series of medical syringe (30, 50 mL capacity) as pulse columns for complete collection of chromium (VI) species present in fresh and industrial wastewater samples at ultra trace low level of chromium (VI) (≤ 0.05 μg mL^− 1). The collected chromium (VI) species onto TPAs⁺Cl⁻ or TPP⁺Br⁻-PUFs was then stripped quantitatively (98-102 ± 2.6%) from the pulse columns with NaOH (2.0 mol L^− 1) and subsequently analyzed photometrically. The chromium (VI) ions could be pre concentrated up to 100-fold from large volume of water samples. The proposed pulse foam columns were applied successfully for complete collection, recovery (97.5 ± 2.6%, n = 5) and subsequent chemical speciation of chromium (III) and (VI) in wastewater samples. The results are in good agreement with the reported and standard methods at 95% confidence.     

An efficient method for the N-arylation of phenylurea via copper catalyzed amidation

The coupling reaction of phenylurea with different functionalized aryl halides in the presence of air stable CuI,N,N-dimethylethylenediamine as a ligand,and K₃PO₄ as a base gives symmetrical and unsymmetrical diarylureas in relatively high yields.This method is milder than the palladium catalyzed arylation and avoids the use of toxic phosphine ligands.     

Synthesis and voltammetric study of some new macrocyclic sulfur compounds for use as chelating agents for separation of arsenic (III) in wastewater and as molluscicidal agents against Biomophalaria Alexandrina Snails

A series of some new nanomeric molecules of cyclic 5- methoxy -5, 6–diaryl -4,5-dihydro -2H-1,2,4–triazin -3-thiones (1-3) has been synthesized. The interaction of compounds 1-3 with HgCl₂ in 1:1 and 1:2 molar ratios was used for the synthesis of the macrocyclic Schiff base [5,6, 11,12 - tetraaryl -1,2,4,7,8,10- hexa-aza cyclododoeca -4,6,10,12- tetraene -3,9-dithione] (4), macrocyclic thioethers 5 and/or complex 6. Chemical structures of the compounds were determined from elemental analysis and spectral measurements. The compounds were screened as molluscicidal agents against Biomophalaria Alexandrina Snails which cause Bilhariziasis. Cyclic voltammetry of selected compounds showed well-defined irreversible electrode couple suggesting application of these compounds as chelating agents for separation of arsenic in industrial wastewater samples. Compound 1 was physically immobilized onto polyurethane foams (PUFs) and was successfully used for complete removal of arsenic (III) & (V) species from wastewater.     

Use of open-cell resilient polyurethane foam loaded with crown ether for the preconcentration of uranium from aqueous solutions

The preconcentration of uranium from aqueous solutions on open-cell resilient polyurethane foams (PUF) impregnated with crown ether as an organic extractant in different conditions was investigated. The data showed that 50 minutes is a sufficient time to attain equilibrium with a maximum extraction percentage for uranium ion on polyurethane foams loaded with crown ether. Also the extraction percentage of uranium is increased markedly with increasing the pH values up to pH ~ 6 and displayed the lowest extraction at 8>pH>6. The different isotherms of uranium sorption have shown that the sorption followed a Freundlich isotherm. Column studies have been carried out in order to extend these studies to the plant scale. From the data of column sorption and breakthrough curves, the height equivalent of theoretical plates (HETP), and breakthrough capacity which affect the efficiency of the column have been calculated and found to be 1.03 mm/plate, 64±5 and 58.3 mg uranium/gram polyurethane foam impregnated with crown ether, respectively.     

Spectrophotometric determination of copper(II) in natural waters, vitamins and certified steel scrap samples using acetophenone-p-chlorophenylthiosemicarbazone

A very simple, highly sensitive and selective spectrophotometric procedure was developed for the determination of copper(II). It is based on the reaction at pH 4–9 between the synthesized acetophenone-p-chlorophenylthiosemicarbazone (A-p-ClPT) and Cu(II) forming a green complex, Cu(II):A-p-ClPT (1:2), that floats quantitatively with oleic acid (HOL) surfactant. It exhibits a constant and maximum absorbance at 600 nm in both aqueous and surfactant layers. Beer’s law is obeyed over the concentration range 0.25–6.35 mg l^?1 with a detection limit of 0.021 mg l^?1 for a standard aqueous solution of Cu(II) with a concentration of 3.82 mg l^?1 (calculated on the basis of 3σ) and molar absorptivities of 5.5 × 10³ and 1.3 × 10⁴ mol l^?1 cm^?1 in aqueous and surfactant layers, respectively. Sandell’s sensitivity was calculated to be 0.244 μg cm^?2 and the relative standard deviation (n = 9) was 0.19%. The different analytical parameters affecting the flotation and determination processes were examined. The proposed procedure has been successfully applied to the analysis of Cu(II) in natural waters, certified scrap steel samples and vitamin samples. The results obtained agree well with those samples analyzed by atomic absorption spectrometry (AAS). Moreover, the flotation mechanism is suggested based on some physical and chemical studies on the solid complexes isolated from aqueous and surfactant layers.