2, Ho Chi Minh University, Ho Chi Minh, , Viet Nam
Membrane technology is recognized as an energy saving option for separation and purification. While already well-established for water desalination, it has great perspective to further expand its application in the purification of aqueous and organic streams. In addition to the most common processes such as ultra- (UF), nanofiltration (NF) and reverse osmosis, by choosing the right combination of chemical composition, morphology and conductivity, membranes can be coupled as key components in energy conversion processes such as fuel cell, electrolysis, pressure retarded osmosis (PRO). Polymeric membranes are typically multilayered. The design of the material to be used in each part and the layer morphologies are crucial for the successful performance in each operating process. The chemistry of the top layer and the porosity and shape of the substrate are important to guarantee high flux, selectivity and fouling resistance. We have been exploring different chemical modifications for the membrane top layer and recent approaches will be discussed in the presentation. A recent approach for the formation of the top layer of membranes to be used in NF or PRO has been to promote the interfacial polymerization of a mixture of (5,10,15,20-(tetra-4-aminophenyl)porphyrin) and m-phenylene diamine with trimesoyl chloride. Porphyrin is a photosensitizer molecule. When the membrane is exposed to visible light, singlet oxygen is generated and its antimicrobial activity is stimulated, minimizing biofouling. Permeation as high as 35 Lm-2h-1bar-1 with 99 % rejection of Brilliant Blue (826 g/mol). Other modifications of the top layer, such as the incorporation of amine-terminated dendrimers and zwitterionic building blocks, are under investigation. Apart from the chemistry itself, adding electron conductivity to the membrane surface layer by incorporating carbon nanotubes or depositing thin metallic layers has been previously demonstrated to increase fouling resistance and extend the use of membranes to bioelectrochemical systems (e. g. microbial fuel cell or electrolysis). The morphology and geometry of the porous substrate is as important for the membrane performance as flat-sheet and hollow fibers. By controlling the bore fluid composition and the spinning conditions of hollow fibers we have been able to systematically tune the porosity and the geometry of the fiber lumen, changing its cross section from triangle to square, pentagon, hexagon and circle.