Highly effective CO2 capture using super-fine PVDF hollow fiber membranes with sub-layer large cavities

This work reports a noticeable advancement in CO2 capture using gas-liquid membrane contactors (GLMC) composed of super-fine poly(vinylidene fluoride) hollow fiber membranes (PVDF HFMs). This is accomplished by incorporating large cavities as a sub-layer beneath the porous upper layer populated with macrovoids in a matrix of an interconnected network of pores. Superimposing rheological images on ternary phase diagrams is considered as a promising and comprehensive tool for interpretation of the observed morphologies in the HFs. Accordingly, the sub-layer cavities are found to evolve when the elastic modulus of HF outer layer (G(o)') in contact with the bore fluid is not high enough to dampen the convective flow driven by the interfacial energy gradient. Implications of the impressive performance of the drawing process on the formation of the large cavities are discussed. Special attention is paid to the greater influence of increasing absorbent flow rate on enhancing CO2 capture efficiency of HFs with large cavities.