optimization of effective parameters on the ligandless extraction of thorium (iv) ions from aqueous solutions by emulsion liquid membrane

: the present paper introduces a technical feasibility study of one of the most advanced extraction techniques; emulsion liquid membrane (elm) on the selective and very efficient transport of thorium (iv) ions from aqueous solutions. the study aims to give a comprehensive account of various parameters that affected the elm formation and stability for increasing the extraction of thorium. in this work, the transport of thorium from aqueous solution occurs through the water-in-oil (w/o) emulsion liquid membrane that constitutes of kerosene as an organic diluent and sorbitan monooleate (span-80) as a surfactant for stabilizing the emulsion phase, sulphuric acid as a stripping solution and potassium chloride as a tracer. the carrier is not used here for emulsification and for the transport of thorium. the influence of ph of the external aqueous phase, the concentration of the acid used in the receiving phase and the mixing speed on the process efficiency were examined and discussed with response surface methodology (rsm) based on central composite design (ccd) [1-4]. the hydrodynamic parameters mentioned above were optimized for achieving the maximum thorium extraction with minimum emulsion breakage and swelling. the optimized conditions showed that the best extraction efficiency and emulsion stability is obtained at ph of donor phase=5; span 80 volume percentage in the membrane phase= 4 % v/v; the sulphuric acid concentration as a stripping solution is 0.6 molar; emulsion/donor phase volume ratio= 0.1, and the effect of volume ratios of the internal phase to the organic phase 1:1 (a/o) and mixing speed = 180 rpm. the role of ph as an important parameter in the elm process for extraction of thorium was studied. with these conditions, the extraction efficiency of 97.84% was obtained within 15 min and the measured values of emulsion breakage and swelling were 0.051% and 0.260%, respectively.