Membrane surface modification: techniques, properties and applications

Conventional membranes are used in membrane emulsification to generate highly uniform droplets over a desired range of droplet sizes, and in microfiltration for the removal of solid particles down to 0.01 microns in size from liquid streams. However, the productivity and operating costs for both of these processes may suffer because the internal pore structure of these membranes can be become blocked during operation, leading to a large pressure drop across the membrane.

Such problems can be avoided by using a special type of membrane called a microsieve, and unlike conventional membranes, microsieves do not have an internal pore structure. The microsieves developed at Micropore Technologies consist of a thin metal sheet with uniformly sized and spaced pores, where each pore forms a direct channel from one side of the membrane to the other.

In this thesis, two surface coatings have been developed to optimise the performance of the microsieves used in membrane emulsification and microfiltration, resulting in two new composite membrane types. The first surface coating was required to improve the uniformity of aqueous droplets formed during the preparation of water-in-oil (w/o) emulsions. The second surface coating was required to remove yeast cells from aqueous feed suspensions. Simple criteria were used in the decision-making process to select the best type of coating, which included performance (droplet uniformity or yeast cell rejection achieved), durability and material costs. This thesis explores the development work for both coatings, and includes brief notes on those coatings that did not meet the criteria.