This lecture discusses the integration of membranes in different processes. A particular emphasis is given to specific features of membranes: 1 - membranes as regulators of transport of target compounds, using diverse mechanisms and driving forces; 2 - design of membrane topography in order to create specific local conditions and improve mass transfer at the membrane surface; 3 - need for real-time, non-invasive monitoring of membrane process, namely using molecular probes, and their impact on process efficiency; 4 - development of strategies for sustainable membrane fabrication, in particular the niche for membranes from biopolymers.
Different examples of transport regulation are presented and discussed. The exploitation of diverse transport mechanisms is illustrated by the use of ion-exchange membranes in the concept of ion-exchange membrane (bio)reactors, where the transport of electrically charged solutes (e.g., micropollutants) is assured by a Donnan transport mechanism associated with a chemical or biochemical conversion that assures the driving force for transport. Also, the role of membranes for regulation of transport is illustrated with the process of protein crystallization and derivatization, where membranes assure not only the establishment of supersaturation conditions but also the controlled transport of heavy elements, required for isomorphous replacement within the protein crystal lattice.
Membrane topography will become a relevant issue as an effective way to promote turbulence locally, at the membrane surface, assuring conditions for a more efficient and economic mass and heat transfer. The use of this approach is illustrated with the development of corrugated membranes by thermal imprinting and their use in a reverse electrodialysis (RED) process. Computational Fluid Dynamics (CFD) studies support the rational design of corrugations at the membrane surface. This issue is becoming progressively more relevant as new membranes offer higher permeability and selectivity. If improved mass transfer conditions at the membrane surface are not offered, these membranes will be useless due to external mass transfer limitations.
Real-time, non-invasive monitoring of membrane processes, at the nano or molecular scale, is discussed namely through the use of on-line mass spectrometry for monitoring pervaporation and gas permeation of complex mixtures, which represents a breakthrough when compared with the usually methods of monitoring of these processes. Also, the use of molecular fluorescent probes that allow for monitoring the transport of specific molecules (namely oxygen) is presented and discussed for several application, such as barrier membranes.
Finally, the concern with the circularity of membrane use is addressed. The production of biolpolymers for the fabrication of membranes and their use in hydrophilic pervaporation and gas dehydration processes is presented and discussed.
João G. Crespo - Professor of Chemical Engineering at the School of Science and Technology – NOVA University of Lisbon, Portugal. Director of the Laboratory of Membrane Processes at iBET. Former Vice-Rector for Research and Innovation and former Coordinator of NOVA Doctoral School. Member of the Portuguese Academy of Engineering. Member of the editorial board of “Journal of Membrane Science”, “Journal of Biotechnology”, “Desalination and Water Treatment” and “Membranes”. Editor of 2 books, 23 book chapters and 290 publications referred in Scopus. Founder of the spin-off company “Zeyton Nutraceuticals”.
Research Keywords: Membrane materials and processes; Bioseparations; Water treatment and valorisation of bioresources; Process Monitoring.