Characterization of Membranes

Membrane processes can solve a wide range of separation problems with a specifically designed membrane system. For determination of membrane type, different membranes must be characterized in terms of physical and structural properties. At the selection of membrane process, membrane characterization is the most important step because the membrane processes are designed according to physical and chemical properties of membranes. The ultimate goal of the membrane technology is to find the proper relationship between membrane fabrication- membrane morphology-membrane performances. Different techniques are used for membrane characterization, some of which are mostly prefered by membrane researchers and manufacturers. The most basic way to characterize membrane is to measure and classify its pore size and pore size distribution. The pore sizes are determined by different methods: microscopic, bubble pressure and gas transport porosimetry, liquid-vapor equilibrium, liquid-solid equilibrium and gas-liquid equilibrium. Another important way is the chemical characterizations of membranes with Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy electron spectroscopy, atomic force microscopy, secondary ion mass spectrometry and surface hydrophilicity and surface energy. This chapter focuses on the physical and chemical characterization methods of pressure-driven membrane processes such as reverse osmosis, nanofiltration, ultrafiltration, and microfiltration.