الفهرس | Only 14 pages are availabe for public view |
Abstract Palladium, molybdenum, zirconium and niobium are among the fission products and are considered as strategic materials The increasing demands of these elements in different industrial and nuclear applications faced with limited and decreasing natural resources (especially for Pd), makes spent nuclear fuel a potential source of these metals and an alternative to mineral contributors. In this context, liquid-liquid extraction, emulsion liquid membrane (ELM) and sorption techniques are employed for the extraction and separation of Pd, Mo, Zr and Nb from nitric acid medium using commercial extractants such as green diesel fuel, CYANEX 471X, CYANEX 923 and Ionquest 801. The different parameters affecting the liquid-liquid extraction process of these metals have been separately studied in terms of shaking time, nitric acid, hydrogen ion, nitrate ion, extractant and metal ion concentration, the phase ratio and temperature, stripping investigations were also studied. The possibility of extraction and recovery of palladium from the sulphate leach solution of spent automotive catalyst using green diesel in kerosene was explored and a modified process is proposed and evaluated. In the ELM investigations for palladium extraction using CYANEX 471X in chloroform as carrier, the effects of the different parameters affecting the membrane stability were studied as well as the kinetics of Pd(II) permeation through the prepared membrane were also discussed and the results indicated that the rate of permeation depends on the carrier, Pd(II), and nitric acid concentration. The extraction of molybdenum (VI) from aqueous nitric acid solution with trialkylphosphine oxide (CYANEX 923) in kerosene as diluent was carried out and the results show that the loading capacity of CYANEX 923 was found to be 0.015 mole of Mo (VI) per mole extractant. In order to test the viability of the used extraction system (CYANEX 923/kerosene) for the extraction of Mo(VI) from its ores, an application study under the optimum experimental conditions was carried out on the Gattar Granite ore. The adsorption of Mo(VI) from nitric acid solution using styrene divinyl benzene copolymer (SM-4) impregnated with 30% CYANEX 923 using batch and column techniques were carried out. The effects of the different parameters affecting the extraction of Mo(VI) such as contact time, nitric acid concentration, V/M ratio, metal ion concentration as well as temperature effect were investigated. The experimental results show that sorption of Mo(VI) obeys Freundlich isotherm. Breakthrough curves indicate that column performs better with low flow rate, concentration and high bed height. An application was also carried out on Gattar granite for the recovery of Mo(VI) from other metals. The extraction of Zr(IV) and Nb(V) from nitric acid solution with IONQUEST 801 in kerosene were also separately studied. The effects of the parameters affecting the extraction process were investigated. Further, the separation feasibility of zirconium and niobium is also discussed based on the experimental results of their extraction and stripping percentages as well as temperature effect. In this respect, two successive separation methods were investigated to separate zirconium from niobium from their admixture and flow sheets which describe the separation process are proposed. In addition, the separation process of the four investigated metals from each other from their mixture in a synthetic solution was investigated. A flow sheet which summaries the proposed method for separation between Pd (II), Mo(VI), Nb (V) and Zr (IV) from 3 M nitric acid is proposed. Key words: Solvent Extraction, CYANEX 923, Emulsion membrane, CYANEX 471X, Sorption, IONQUEST 801, , Nitrate medium, palladium, molybdenum, zirconium, niobium. |