Hollow Fiber-Contained Liquid Membranes for Separations: An Overview

Abstract

The basic technique of hollow fiber-contained liquid membrane (HFCLM) permeation-based separation of gas mixtures and liquid solutions is reviewed and existing applications in organic acid/antibiotic recovery from fermentation broths, facilitated, countertransport and co-transport of heavy metals, facilitated CO 2 -N 2 (CH 4 ) separation, and facilitated SO 2 -NO x separation from flue gas are surveyed. New applications of the HFCLM technique include separations of organic mixtures (including isomeric) through polar liquid membranes (including cyclodextrin-containing aqueous solutions), highly selective pervaporation of organics from water, and, for gas separation, a modified technique that can treat feed at 175-200 psig. The utility of HFCLM as a reaction medium as well as the separator in separation-reaction-separation and separation-reaction processes will also be illustrated.The utility of a thin layer of liquid as a selective membrane for separations has been explored extensively over the last thirty years. Three techniques have been used traditionally to exploit a thin liquid layer as a membrane: emulsion liquid membranes (ELM) for separation of liquid solutions (/); supported liquid membranes (SLM) in the pores of a porous/microporous support membrane for the separation of liquid feeds; and immobilized liquid membranes (ILM) in the pores of a porous/microporous support membrane for separating a gas mixture. SLM and ILM are different names for the same liquid membrane technique and have been briefly reviewed by Majumdar et al. (2) and Boyadzhiev and Lazarova (3).A more recent liquid membrane technique is the hollow fiber-contained liquid membrane technique which is sometimes abbreviated as the CLM technique or the HFCLM technique. This technique has overcome most of the shortcomings of the SLM/ILM techniques. First introduced during 1986-1988 (4,5), the CLM-based permeation technique is undergoing evolution. This paper will provide a brief

Membranes, Phase Interfaces, and Separations: Novel Techniques and Membranes—An Overview

“…Since the shell-side liquid membrane may be connected to an external reservoir as well as a liquid discharge outlet, the liquid membrane instability encountered in ILMs and SLMs is eliminated. 80 Larger-scale developments of such modules for a variety of separations, especially gas separations for CO 2 removal, are taking place. 81 This physical configuration of a HFCLM allows the development of not only two bulk fluid phase interfaces but also two cell-fluid interfaces or enzyme-fluid interfaces for enzymefacilitated reaction and separation of a difficult-to-separate mixture of organic acids.…”

“…This is the basis of the hollow-fiber-contained liquid membrane (HFCLM). Since the shell-side liquid membrane may be connected to an external reservoir as well as a liquid discharge outlet, the liquid membrane instability encountered in ILMs and SLMs is eliminated . Larger-scale developments of such modules for a variety of separations, especially gas separations for CO 2 removal, are taking place…”