Porous Membrane

Membrane processes can cover a wide range of separation problems [with a specific membrane (membrane structure) required for every problem]. Thus, there are membranes available that differ in their structure and consequently in the functionality. Therefore membrane characterization is necessary to ascertain, which membrane may be used for a certain separation. Membranes of pore size ranging from 100nm to 1μm with a uniform pore size are very important in membrane technology. An optimum performance is achieved when the membrane is as thin as possible having a uniform pore size. Here in this thesis, membranes were synthesized by particle assisted wetting using mono-layers of silica colloids as templates for pores along with polymerizable organic liquids on water surface. The pore size reflects the original shape of the particles. Thus it is possible to tune the pore size by varying the particle size. This method is effective to control pore sizes of membranes by choosing silica particles of suitable size. This approach gives a porous structure that is very thin, but unfortunately limited in mechanical stability. Thus there is a need for support which is robust and can withstand the various mechanical stresses. A small change in the membrane or defect in the layered structure during the membrane formation can have drastic effect on the assembly. Lateral homogeneity of the layer generated by the particle assisted wetting can be judged by examination of its reflectivity, but once it is transferred on any solid support this option is no more. So a method is needed to detect the cracks or the inhomogenity of the membrane which can be detected even after the transfer. To tackle this problem a very simple and novel technique for characterizing the membrane by fluorescence labeling and optical inspection was developed in this thesis. The idea was to add a fluorescent dye which is poorly water soluble to the spreading solution comprising of the particles and the monomer. If the dye survived the photo-cross linking, then it would be embedded in the cross-linked polymer and would serve as a marker. Defects and inhomogenity would show up as cracks and spots. By the method that we have developed, we can detect our membrane from the support and spot defects