Progress in membrane science and technology for seawater desalination — a review

Abstract

It is imperative to review the history of the past to provide a vision for the future. It is therefore the objective of this paper to review the history of the development of membranes and membrane processes for water production in general and seawater desalination in particular. The review highlights some new trends observable in the following four areas; membrane development, membrane characterization, membrane transport and membrane system design. The future prospects in the above four areas are discussed. Membrane development deals with recent progresses in the development of reverse osmosis membranes used for desalination. There are two different approaches, both based on in-situ polycondensation technique. One is to develop membranes for desalination of brackish water operable at ultralow pressures, and the other is to develop membranes operable at high pressure to achieve high pure water recovery in seawater desalination. In membrane characterization section, Atomic Force Microscopy (AFM) is featured as a new tool to investigate membrane surfaces. The effects of surface roughness, which can be measured by AFM, on membrane productivity and membrane fouling are discussed. Electron Spin Resonance (ESR) is another method, the application of which to investigate synthetic membranes has only begun. The potential of this method to investigate the structure of the membrane is discussed. Recent progresses in the measurement of pore sizes as small as one nanometer are briefly described. Membrane transport deals with transport models made primarily for charged membranes. Since most of nanofiltration membranes are electrically charged, the development of such transport models is useful in water treatment by nanofiltration membranes. Transport models in which pore sizes are included explicitly are particularly important since pore sizes of nanofiltration membranes are measurable. The section in membrane system design deals with various hybrid systems for seawater desalination in which membrane processes are incorporated. There is a great potential to reduce desalination cost by combining membrane processes with more conventional unit processes.