Effects of Contamination on Plate Column Extraction

Abstract

In the previous papers it was shown that with many systems, the rates of extraction from drops during their free rising were greatly decreased by the contamination of the systems with a trace amount of poisonous contaminating substances. In this paper, results of further studies on the effects of contamination are reported to make clear the total amount of mass transfer through one plate with one nozzle (DN=0.101cm) (Cf. Fig. 1), in which the acetic acid is transferred from the dispersed phase of benzene to the continuous phase of water. Said total amount is affected not only by the amount of transfer during the free rising of drops which was already reported in the previous papers but also by the end effects of both coalescence and drop-forming.Experimental results of l=5.0cm are shown in Fig. 2 for contaminated and non-contaminated systems, where it is shown that for both the systems, the rates are approximately the same, although in the case of drops reported previously, it was very small. This may be due to the large end effects of contaminated systems to compensate the decrease in extraction during free rising of the drops. The end effect at the time of drop forming ought to be considerably large as shown in Fig. 2, but it actually tells little, because the time required for drop-forming from liquid jet is too short to allow the drop to absorb the contaminating substance on to its surface.Coalescence effect is also large in contaminated system, because, while in non-contaminated system the drops are broken down as soon as they reach the interface, in contaminated system, the drops are not broken but are accumulated at the interface and the solute is transferred during this accumulation.Consequently, it is no use in the case of contaminated system to increase the plate distance so as to increase the total amount of extraction for one stage, unlike in the case of non-contaminated system. (Cf. Fig. 3.)The effects of concentration of contaminating substance and column height on the extracted acid percent were investigated into and one example of the results of these experiments is given in Fig. 5.