Development of membranes with regions with different characteristics by phase inversion technique

Abstract

Separation membrane cells comprising membrane sections with different characteristics can be the base for new separation processes. Hybrid membrane cells require new membranes with regions with different characteristics. In this paper we present numerical and experimental approaches to develop such membranes by the phase inversion technique. The two main steps of the phase inversion technique, the evaporation step and the immersion precipitation step, are studied by numerical methods. The numerical approach is based on the solution of the mass transport equation to predict the film composition after the evaporation step and in the solution of the CahnHilliard equations to predict the structure of the membrane after the immersion precipitation step. The equations are solved by finite difference methods. The numerical simulations are used to predict the influence of several experimental parameters (temperature, composition of the initial polymeric solution, evaporation time, precipitation time, immersion bath composition) in the structure of the membrane. The experimental approach is based on the manipulation of the experimental conditions to produce regions of different characteristics in the same membrane. An experimental method to create different regions from two different initial polymeric solutions is presented.