Effect of Concentration of the Height of a Transfer Unit in a Liquid/Liquid Solvent-Extraction System

摘要

Pulsed, sieve-plate extraction columns were used to examine the effect of solute concentration on extraction efficiency. Cerium was extracted from an aqueous coprocessing solution, simulating reprocessing wastes produced at the Idaho Chemical Processing Plant. The organic extractant used in this process was dihexyl-N, N-diethylcarbamylmethylene phosphonate. Subsequently, cerium was stripped from the organic phase with 0.05 M nitric acid. The Heights of a Transfer Unit were calculated from the extraction and stripping column operating data. Both interstage and overall transfer units were calculated. Nine extraction and nine stripping tests were performed. Three extraction feed concentrations, each repeated at three different pulse frequencies were used to study the affect of concentration on height of a transfer unit. The stripping column was operated simultaneously with the extraction column. Both columns were operated at pulse amplitudes of 2.5 cm. Data based upon the overall extraction column showed a slight decrease in the height of a transfer unit as the solute concentration decreased. Based upon the overall stripping column data, a decrease in solute concentration resulted in a very slight increase in the height of a transfer unit. However, interstage transfer unit calculations for both columns indicated solute concentration had no significant effect on the height of a transfer unit. Based on the experimental tests, it was concluded that solute concentration caused only slight changes in extraction efficiency for the concentration range studied. Other factors such as pulse frequency, aqueous/organic flow ratio, and possibly the dispersed phase bubble size had a much greater effect on the extraction efficiency for the system studied. (ERA citation 06:031703)