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Abstract  

Experiments on sorption of cobalt onto polyethylene foil from buffered borate solutions are reported in this paper. Sorption isotherms and sorption kinetics of cobalt as a function of pH and the effect of borate species on cobalt sorption were investigated. The results show that the extent of cobalt sorption is lower in borate buffer than in Na ClO4 solution. It is found that the adsorption isotherms obtained are dependent on the pH of the solution. Possible reasons of the influence of pH on the sorption isotherms are discussed.

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Extraction of cobalt(II) with 7-(1-decenyl)-8-quinolinol (HRql) into chloroform was examined. The best cobalt extraction occurs in the pH region 5.5–9. In this region several other cations are extracted. The values of Kex and pH0.5 for cobalt extraction were found to be −8.6 and 3.19 respectively. The composition of the extracted complex was found to be Co(Rql)3. Cobalt is poorly reextracted from Co-HRql complex into the aqueous phase, the best results were obtained using HCl as a stripping agent.

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A bench-scale method was developed to remove cobalt- and mercury-EDTA chelates from water onto macroporous char. Experimental parameters included variations on solution pH, char pre-treatment, cobalt oxidation state, and apparatus configuration. The use of 60Co and 203Hg radiotracers allowed for total accountability of the metals in the char and effluents. Overall experimental results demonstrate the applicability of treated macroporous chars for the effective removal of both cobalt and mercury EDTA chelates from aqueous solutions. The char system was optimized to sequester 97.5% and 99.8% of the cobalt- and mercury-EDTA from 20 ppm solutions, respectively.

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Many factors affect the ion exchange process in zeolites. In this work the influence of different anions such as acetate, chloride and nitrate on the ion exchange of cobalt in zeolite ZSM-5 is discussed. After the ion exchange in the presence of those anions no change was found in the zeolite structure, by X ray diffraction and IR spectroscopy. The retention of cobalt by zeolite ZSM-5 at low concentrations (from 0.001 to 0.3N) was higher when the exchange was done with cobalt nitrate and chloride. This behavior was different in the case of 1N cobalt salts, since the highest sorption uptake was found when working with cobalt acetate and its sorption was directly proportional to its concentration.

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The partition behaviour of cobalt into 4-(5-nonyl)pyridine (NPy) in benzene from aqueous hydrochloric, nitric and sulfuric acid media containing variable amounts of potassium thiocyanate is described. Cobalt is quantitatively extracted by NPy from 0.1–1M KSCN solutions at 0.01 M concentration of the mineral acids. The extraction mechanism and the possible compositions of the extracted species are discussed. The effects of foreign salts on the extraction of cobalt from three mineral acid solutions are reported. Several elements including those which are of some interest in connection with the separation of cobalt were tested for extraction from 0.01 M solutions of mineral acids 0.3 M with respect to KSCN and their factors for separation from cobalt were estimated.

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Abstract  

A continuous extraction device for preconcentration of metals with light phase internal recycle has been developed. This system was used for preconcentration of cobalt and uranium from 20–30 dm3 samples with 10.8 dm3/hours feed rate. The emulsion membranes were created of surfactants and LIX 64 N (for cobalt) or di-2ethylhexyl-phosphoric acid (for uranium) as a carrier to control stability and permeability for long time periods. The results from continuous extraction of cobalt and uranium using the device constructed have shown the possibility to reach 100–200-fold preconcentration of metals with high yield (min. 92%).

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Abstract  

The extraction of strontium and cesium ions from high ionic strength acid, base, and salt solutions into an organic extractant consisting of alkyl cobalt dicarbollide and polyethylene glycol (PEG) in diethylbenzene was investigated. Adding hexaethylene glycol or PEG-400 improved the strontium extraction ≥100-fold, while cesium extraction was decreased at high PEG concentrations. The extractions are rapid and selective, even in the presence of molar concentrations of sodium ion, suggesting that alkyl cobalt dicarbollide extractants are useful for the treatment of alkaline nuclear wastes. A method for the synthesis of tetra-n-hexyl(cobalt dicarbollide) is described.

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Abstract  

A method of radioactivation analysis has been developed for the substoichiometric determination of cobalt, copper and manganese in glass and glass-making materials. The substoichiometric extraction of cobalt with α-nitroso-β-naphthol was studied and simple procedures are suggested for the determination of the three elements. Cobalt is extracted substoichiometrically as α-nitroso-β-naphtholate into chloroform from solution of pH 6.2, copper as dithizonate in carbon tetrachloride from weak acidic solution, and manganese as tetraphenylarsonium permanganate into chloroform after oxidation to permanganate. Contents from 2 ppm to 3 ppb of cobalt, copper and managanese were analysed in glass-making materials, and it is shown that the method for their determination is reliable and superior in accuracy and reproducibility.

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Abstract  

A study of the distribution of cobalt between mineral acid solutions containing potassium thiocyanate and 0.1M 2-hexylpyridine in benzene has been undertaken. Cobalt can be quantitatively extracted as its thiocyanate complex from very dilute acid solutions containing 0.1–1M KSCN. Variation of the distribution coefficient DCo in terms of the ligand concentration in the organic phase has allowed the formula of the extracted species to be determined as Co(HPy)4 (SCN)2. The effects of oxalate, acetate, fluoride, ascorbate, sulphate and thiosulphate ions on the extraction of cobalt from three mineral acid solutions have been reported. The extraction coefficients of several elements are given for the 0.1M 2-hexylpyridine in three systems containing 0.5M KSCN with 0.25M HNO3, 0.05M HCl and 0.05M H2SO4 respectively; and their factors for separation from cobalt are estimated.

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Abstract  

A radiochemical displacement method was utilized for the determination of traces of mercury in water taking advantage of its ability to displace cobalt from cobalt(III) diethyldithiocarbamate tagged with60Co. The method is found to be applicable in the concentration range of 50–200 g/ml mercury. The interfernces from various cations like Fe(III), Co(II), Cu(II), Pb(II) and Ag(I) ions were studied.

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