Pertraction of phenol in hollow-fiber membrane contactors

In this paper the multistage membrane pertraction (simultaneous extraction and reextraction) of phenol with linear monoalkyl cyclohexane (lMACH) as a carrier and sodium hydroxide solution as a strip, in laboratory scaled pertractors with polysulphone hollow-fiber membranes, was investigated. Two types of pertractors were used, one being “fiber-in-fiber” type, and the other “fiber-by-fiber” type, both with parallel countercurrent flow of three independent liquid streams (feed, extragent and strip). The best results were obtained with feed and strip flow rates low and equal, while the organic flow rate was four times higher. Efficiency is higher for lower phenol concentration in feed, and higher alkalinity of stripping solution. It was shown that the pertraction of phenol with lMACH as an organic carrier is an extraction step-limited process. For that reason the “fiber-by-fiber” type of pertractor offers better constructive possibilities, since it enables combining larger number of fibers for extraction step with a corresponding smaller number of fibers for the stripping step, which is not possible in the case of the “fiber-in-fiber” type of pertractor.

It has been shown that the pertraction efficiency increases with decreasing the feed flow rate, and increasing the extractant flow rate. However, a change in the strip flow rate almost does not affect the efficiency of pertraction. The best results were obtained with feed and strip flow rates low and equal, while the organic flow rate was four times higher. The efficiency is higher for lower phenol concentration in the feed, and higher alkalinity of the stripping solution. Pertraction of phenol with lMACH as an organic carrier is an extraction step-limited process. For that reason, the “fiber-by-fiber” type of pertractor offers better constructive possibilities, since it enables combining a larger number of fibers for –6 the extraction step with a corresponding smaller number of fibers for the stripping step, which is not possible in the case of the “fiber-in-fiber” type of pertractor.