Purely extraction and separation of mixture of cerium(IV) and lanthanum(III) via hollow fiber supported liquid membrane

We have examined the separation of tetravalent and trivalent lanthanide ions, Cerium(IV) and Lanthanum(III), respectively, from sulfate media through a liquid membrane. Tri-n-octylamine (TOA) was used as an extractant dissolved in kerosene. The liquid membrane was supported by a hollow-fiber microporous. Sodium carbonate was used in the recovery solution. Pure Cerium(IV) ions were extracted and recovered, but Lanthanum(III) ions were not extracted by TOA because of the different forms of the Cerium(IV) and Lanthanum(Ill) ions in the sulfate solution. The transport system was studied as a function of several variables: the concentration of the sulfuric acid feed solution, the concentration of TOA in the liquid membrane, the concentration of sodium carbonate in the stripping solution, the flow rates of the feed and stripping solutions and the Lanthanum(III) that remained in the raffinate. The results indicate that the percentage extraction was highly dependent on the concentration of sulfuric acid in the feed solution; a concentration of 0.2 M provided the maximum extraction. The percentage extraction of cerium was enhanced when the concentration of TOA was increased. However, when the concentration of TOA was higher than 5 % (v/v) the percentage extraction no longer increased because of the increased viscosity of the liquid membrane. The influence of the sodium carbonate concentration in the recovery solution of each column was also studied; we found that the extraction and recovery percentages increased further because of differences in the driving force until the sodium carbonate concentration reached 1.0 M, and these phenomena also occur in recovery phase. The maximum percentage of recovery for Cerium(I V) was 67 %; 100 % selectivity was obtained.