SummaryMembrane distillation can only be applied on liquid mixtures which do not wet, a microporous hydrophobic membrane. Solutions of inorganic material in water have such high values of surface tension ( y,_ 2 72 X lo-" N/m) that the non-wetting condition is fulfilled for a number of hydrophobic membranes. As soon as orgamc solutes are present m the solution, the surface tension ;>I> will be lowered, and if the concentration of organic material becomes too high, wetting of the membrane will occur. By means of theoretical considerations a critical solute concentration or surface tension at which a homogeneous smooth material will be wetted (0 < 90' ) can be calculated. For (micro)porous membranes no such theoretical relation can be derived. Therefore, a simple experimental method is described to measure the maximum allowable concentration for a (micro)porous membrane. On the basis of these measurements, the maximum allowable concentration under process conditions can be determined

This paper presents a state of art review on the stability of supported liquid membranes (SLM). The backgrounds of SLM instability phenomena are presented, and various mechanisms for explaining these phenomena are treated in detail. Several suggestions for stability improvement are discussed.

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Permporometry IS a method by which the characterlstlcs of the mterconnectmg 'active' pores of an ultrafiltration membrane can be measured It 1s these 'active' pores that are responsible for the actual membrane performance Apphcatlon of permporometry on different membrane types, including ceramic as well as polymeric membranes, shows that the method can provide obJectwe mformatlon on the 'active' pore sizes present

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