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  • Author or Editor: S. Ahmed x
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Abstract  

Open cell polyurethane foam coated with long chain tertiary amines (Adogen) has been shown to be an effective extractant for uranium in acidic solutions (3>pH>1). With dodecyl alcohol present uranium extraction at pH<1 is effective. The coated foam allowed column flow extraction at high flow rates but capacity studies indicated that only a fraction (about 1/3 to 1/2) of the amine was available for the complexation of the uranium. Interference of some common metal cations indicated that only Co(II) showed a significant adverse effect on the uranium extraction.

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Abstract  

Thermokinetic parameters of the solid-state of poly(o-toluidine) (POT) doped with perchloric (HClO4) acid was studied by thermogravimetric analysis (TG) and differential thermal analysis (DTA) under non-isothermal conditions. Molecular mechanics (MM) calculations suggest that the optimal geometric structure (OMG) of the HClO4-doped POT is at least four orders of magnitude more stable than the molecular geometric (MG) structure. These calculations indicate that the potential energy (PE/kJ mol−1) of the OMG is about four (1.09·104) orders of magnitude lower than the MG structure of the same matrix. The empirical formula of the doped polymer is best represented by [POT-2HClO4·2H2O]n as substantiate by elemental analysis and MM calculations. The full polymer decomposition and degradation were found to occur in three stages during the temperature increase. The decomposition activation energy (E d) of HClO4-doped POT matrix was calculated by employing different approximations. The heating rate (α) of the decomposition and the frequency factor (K o) were calculated. A number of equations were used to evaluate the kinetic parameters. The mechanism of the degradation of the conducting polymer is explained on the basis of their kinetic parameters. A remarkable heating rate dependence of the decomposition rate was observed.

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Abstract  

A radiochemical neutron activation analysis procedure has been applied to investigate 40 major, minor, and trace impurities in nickel-based alloy. The extensive use of these alloys in the electronic industry, telecommunications, manufacturing of aircraft engine turbine blades and chemical equipments desires for their precise characterization. The concentration of nickel in the nickel-based alloy was found to be 56.8%, whereas Fe, Cr, Ca, Mg, Ce, Mn, Na and V were the major components of the alloy, which constituted to more than 26%. The rest of the elements was present in minor or trace levels. Most of the rare earth elements except Ce were also present in trace amounts. Neutron activation analysis technique was preferably used because of its good sensitivity and multielement determination capabilities for the characterization of high purity materials. The comparison of RNAA and INAA indicated improvement in the detection limits utilizing radiochemical separation procedures developed in the present work.

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Abstract  

Extraction of Pr(III), Ho(III) and Er(III) has been studied in the pH range of 1–10 with N-benzoyl-N-phenylhydroxylamine (BPHA) in benzene. The separation was found to be quantitative in borate media from pH 7 to 10, at an ionic strength of 0.1M (H+, BO3 3–). The stoichiometric composition of the complexes under the optimal conditions of shaking time, pH and reagent concentration was formulated using slope analysis and found to be M(BPHA)3, where M=Pr(III), Ho(III) and Er(III). The effect of various masking agents shows that citrate, ascorbate, EDTA, oxalate, fluoride and phosphate form stable complexes with these rare earths as compared to BPHA. The decontamination factors for different cations with respect to these rare earths under the optimum conditions have been evaluated.

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Abstract  

Et(Ind)2ZrCl2 and MAO co-catalyst, which polymerize ethylene and propylene, were heterogenized on partially dehydroxylated Davison silica 955, following the method of equilibrium adsorption. The dispersion of these catalyst components on the silica support was investigated by measuring the spatial concentration profiles of Si, Al, and Zr using a micro-PIXE technique. These components were found to be uniformly distributed over the support irrespective of the variation in the heterogenization procedures and the experimental conditions used. The Si∶Al ratios determined by the micro-PIXE technique were similar to those measured by the spectrophotometric method. However, the Al∶Zr ratios measured by the former were somewhat lower than those determined by the latter. Micro-PIXE measurements confirmed the presence of several trace impurities such as K, Ca, Ti, Fe, Ni, Cu, and Zn which may potentially poison the resulting catalyst.

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Abstract  

Liquid — liquid extraction of Ag(I) by diphenyl-2-pyridylmethane (DPPM) in benzene from aqueous nitric and sulfuric acid solutions containing thiocyanate ions has been studied at ambient temperature (24±2 °C). The metal is extracted quantitatively from 0.01M HNO3+0.02M KSCN; or 0.25M H2SO4+0.02M KSCN by 0.1M DPPM (optimum extraction conditions). Slope analysis indicates that two types of ion-pair complexes i.e. [(DPPMH)+·Ag(SCN) 2 ] and [(DPPMH) 2 + ·Ag(SCN) 3 2– ] are involved in the extraction process. Separation factors determined at optimum conditions reveal the separation of Ag(I) from Cs(I), Br(I), Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Fe(III), Au(III) (from HNO3 solution only), Cr(III), Hf(IV), Ta(V), Sn(IV) and Cr(VI). With the exception of thiosulfate, other complexing anions like ascorbate, acetate, citrate, oxalate do not hinder the extraction of Ag(I) under optimum conditions.

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Abstract  

The uptake of Zn(II)-SCN complex onto polyurethane foam (PUF) has been investigated in detail with respect to different composition and variable concentration of electrolyte, zinc, thiocyanate ions and PUF, and equilibration time. The sorption data followed both Langmuir and Dubinin-Radushkevich (D-R) sorption isotherms over the entire concentration range of zinc investigated whereas Freundlich sorption isotherm is obeyed upto 13.6.10-3M concentration. The Langmuir constants Q = 202±7 mmole.g-1 and of b = (1.78±0.31.104 dm3.mole-1 and of D-R paraneter X m = 493±1 mmole.g-1, b = activity coefficient = -0.028±0.0002 and of sorption energy E = 13.2±0.5 kJ.mole-1 and Freundlich constants 1/n = 0.42±0.03 and c m = 6.47±1.7 mmole.g-1 were evaluated. The influence of temperature variation on sorption have yielded DH = -77.5±2.9 kJ.mole-1, DS = -5±0.09 J.mole-1.K-1 and DG = -6.67±0.05 kJ.mole-1. The effect of common anions and cations on the sorption has been examined. Sulphate, ascorbate and bromide ions enhances the sorption to some extent whereas nitrite, Pb(II), Fe(III), Al(III), Cu(II) and Co(II) decrease to sorption significantly. A possible mechanism has been envisaged for Zn(II)-SCN sorption onto PUF.

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Abstract  

The sorption of 60Co, 65Zn, 75Se, 103Pd, 110Ag and 203Hg radionuclides by polyurethane foam (PUF) was investigated and optimized with respect to the selection of appropriate sorptive medium, metal, thiocyanate ions (except for 110Ag) and PUF concentration and equilibration time. The influence of common anions and cations on the sorption of each metal was examined. The sorption data subjected to different sorption isotherms have shown that the sorption of all the radionuclides followed Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherms. The sorption capacity intensity and energy were evaluated for each element studied. The variation of sorption with temperature was monitored for all radionuclides except zinc and selenium. The values of H, S and G were estimated and found to be negative indicating exothermic and spontaneous nature of sorption. It was found that PUF is an effective and economical sorbent for traces of metal ions which can be used for the separation/preconcentration of these ions from their very dilute solutions and has useful applications in radioanalytical and environmental chemistry and in radioactive and industrial liquid waste management.

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Phytoremediation is a green technology for the sustainable remediation of surface soils contaminated with toxic heavy metals. When added to soils the chelating agent ethylenediamine tetraacetic acid (EDTA) increased the solubility of heavy elements for plant uptake during phytoremediation. A greenhouse experiment was carried out with two Brassica species (Brassica juncea and Brassica carinata) grown on artificially contaminated soil (20 and 40 mg Cd kg-1) with EDTA added at a rate of 1 g kg-1 soil. With increasing Cd (0, 20 and 40 mg Cd kg-1 soil) contamination the biomass of both the Brassica species decreased. However, Brassica juncea was more tolerant of high levels of Cd in the soil in comparison to B. carinata. The results indicated that EDTA made the cadmium more available to the plants and lowered the Cd content of the soil. The magnitude of the increase in tissue (stem, leaf and root) Cd concentration was higher in B. juncea than in B. carinata and after the application of chelating agent (EDTA). The Brassica juncea species of Indian mustard has better potential for the phytoremediation of soil heavily contaminated with Cd (40 mg Cd kg-1 soil).

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Abstract  

Single crystals of the organometallic material tetra(thiourea)copper(I) chloride (TTCC) were grown from aqueous solution. It is interesting to observe that Co2+-doping influences the efficiency of some of the physical properties of TTCC. Presence of Co2+ ions in the doped specimen is confirmed by energy dispersive X-ray spectroscopy (EDS) and chemical tests. FTIR studies reveal that the binding of thiourea with copper chloride occurs through sulphur. Doping results in reduction in the intensity of XRD peaks. SEMreveals that doping results in layered growth of the crystal. DSC confirms slight variations in the decomposition pattern. Mechanical stability of the doped specimen is much better than TTCC. Optical transparency is slightly enhanced by doping and a wide transmission in the visible region is observed. TTCC is non-linear optics (NLO) inactive and the second harmonic generation (SHG) efficiency is not influenced much by the added dopant.

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