چكيده به لاتين
The aim of this thesis was the study on the simultaneous effects of nanoparticles and surfactant on the stability of emulsion liquid membrane (ELM) for the separation of uranium and rare earth metals of gadolinium and neodymium. In order to this purpose, six major series of experiments were done. For the first Seri, the extraction of Gd(III) with D2EHPA in ELM from acidic solution was evaluated. Important variables affecting the ELM performance were systematically investigated and the optimum conditions were obtained. Results indicated that at the optimum condition, simultaneous quantitative extraction (>99%) and stripping (>79%) of Gd(III) were achieved. In second Seri, an emulsion nanofluid membrane (ENM) was applied to effectively extract Gd(III). Simultaneous emulsification of nanoparticles and surfactant was performed to stabilize the ENM. Multi-walled carbon nanotubes (MWCNTs) nanofluid was employed as liquid membrane and CYANEX 272 as carrier. Results indicated that presence of MWCNTs led to 45.8% and 62.9% reduction in membrane swelling and breakage, respectively. Furtheremore, MWCNTs caused to enhanced overall mass transfer coefficient about 97%. Under the optimized conditions, the extraction of Gd(III) reached the maximum of 92.05%. In the third Seri, Study on the Nd(III) extraction with CYANEX 272 through MWCNTs assisted ELM has been performed. At the optimum condition, the extraction of Nd(III) reached the maximum of 99.03%. At the forth Seri, the novel extractant, CYANEX 572, was applied for selective separation and enrichment of Nd(III) and Gd(III) through an ELM. Under the optimum condition, the extraction percentage of Gd(III) was maximum (67.45%), while the extraction percentages of Nd(III) was minimum (28.98) and the separation factor was found to be 3.78. The stripping efficiency and enrichment factor reached the maximum of 89.04% and 12.01 for Gd(III), and 19.45% and 1.13 for Nd(III). For the fifth Seri, selective extraction of uranium from Nd(III) and Gd(III) using C572 through an ELM was investigated. Taguchi (L9) method with four variables was performed. Results indicated that U(VI) was completely extracted and separation factor of U(VI)/Gd(III), U(VI)/Nd(III) were achieved 78.72 and 76.36, respectively. For the last Seri, the simultaneous effects of nanoparticles and surfactant on the mean drop size of the continuous ELM system in a horizontal mixer-settler were studied. Results indicated that presence of MWCNTs and Span-85 at the same time, caused to a remarkable reduction in drop size about 66%. In order to predict mean drop size, a new modified correlation was suggested where the surfactants and nanoparticles concentrations were introduced as new independent parameters.
