Solvent extraction in columns in a droplet breakage domain.

Extraction of metals in columns is scarce despite the advantage of low solvent inventory and the feasibility of high throughputs. Fast extraction kinetics allow short residence times and thus small apparatus height. A simulation of column concentration profiles via droplet population balances is less sophisticated as with surface active ion exchangers droplet breakage dominates and coalescence is hindered (rigid droplet surface). The extraction of Zn with D2EHPA (di(2-ethylhexyl)phosphoric acid) in a countercurrent Kühni column was investigated and the impact of different breakage kernels analyzed. Experiments in a lab scale test cell based on a DN32 Kühni extraction column geometry gave the basis to validate existing correlations and kernels for droplet breakage probability and daughter droplet size distribution. Since single droplet breakage tests were performed, a breakage dominated regime prevailed in the investigations. This yielded into a new unified correlation for the latter valid for different column geometries and physical and reactive extraction systems. As to this, a more firm basis for the simulation and design of stirred columns in hydrometallurgical application is established. [ABSTRACT FROM AUTHOR]