| Nickel/Cobalt separation was achieved in a pulsed sieve-plate extraction column using di(2-ethyl hexyl) phosphoric acid as the extractant. The liquid-liquid mass transfer involved in this process has been studied.;The value of the coefficients were in the 0.2 x 10-3 to 1.8 x 10-3cm/sec. range for cobalt, and 0.5 x 10-3 to 2.4 x 10-3cm/sec. for nickel.;By applying the pulsing technique to increase the degree of mixing between the two phases, the mass transfer rate was found to be significantly enhanced. The comparison of mass transfer coefficients with values obtained using different pulse amplitudes indicated that the coefficient value increased as the amplitude increased. The coefficient was also observed to be affected by the direction of mass transfer, such that the mass transfer coefficients for extraction were found to be higher than those obtained in stripping.;To evaluate the mass transfer characteristics of the operation, steady-state concentration profiles along the column were obtained by sampling both phases from each plate. Droplet size and interfacial area were estimated using a photographic method. From this information, the overall mass transfer coefficients in different sections of the column were calculated, and were found to vary with the concentration during the extraction, but remained rather constant during scrubbing and stripping. |
