Direct contact membrane distillation for nuclear desalination. Part I: Review of membranes used in membrane distillation and methods for their characterisation

Membrane distillation (MD) is a relatively novel membrane technology considered by the researchers as a potential method for seawater desalination. In the first issue of this journal, the possibility of nuclear desalination by MD was discussed comparing various MD configurations. The present paper firstly reviews the membranes used in MD and the methods of their characterisation, among them wet/dry flow method, gas permeation test, scanning electron microscopy, field emission scanning electron microscopy and atomic force microscopy. The membrane parameters, which have to be known before selection of the membranes for some specific applications such as liquid entry pressure of water, pore size, pore size distribution, porosity and pore tortuosity, were determined. The knowledge on membranes themselves, membrane materials and morphology is very important for engineering of polymer barriers for MD and development of industrial membrane units. The availability of the industrial MD modules is up to now one of the limitations for further process implementation.