Multicomponent and Contamination Effects on Mass Transfer in a Liquid–Liquid Extraction Rotating Disc Contactor

Abstract

The intention of this work was to show the relation between mass transfer coefficients for ternary and quaternary liquid-liquid systems that can be experimentally obtained from relatively simple single drop experiments and the extraction performance of a pilot-plant rotating disc contactor extraction column (RDC). For the ternary toluene-acetone-water system and relatively low hold-up, mass transfer coefficients were the same in the RDC as for single drops. However, a different picture was obtained for experiments where phenol was present—either in the ternary or the quaternary system: it was not possible to simulate the pilot-plant mass balance operating lines with the mass transfer coefficients derived from the single drop experiments with the same solution. This finding is valid for acetone as well as phenol mass transfer. The reason for this is thought to be agitation-dependent interfacial tension effects on mass transfer coefficients, and perhaps also a change in the hydrodynamic condition inside the column when phenol is present since the hydrodynamic simulation-software used does not predict the effects of inhomogeneous hold-up conditions. A similar picture can be drawn for the experiments with additional contamination with SDS. Multi-component interactions between mass transfer coefficients for phenol and acetone seemed unimportant for the solute concentrations used (ca. 1 wt%). Repeated counter-current experiments (with solutions made up at different times) showed a repeatability of concentration measurements of better than 95%, and number of plug flow transfer units was very similar, so experimental errors do not invalidate the findings.