Electrical driven reverse osmosis membranes for water purification
Post-doctoral allowance, AAP 2019
Team: Laboratoire de Physique Statistique (LPS), Micromégas team
Project leader: Alessandro Siria
Abstract:
Filtering and separating specific molecules is a vital challenge, from the intensive production of clean water to biomedical applications. Most modern processes for filtration are based on passive sieving principles: a membrane with specific pore properties allows separating the permeating components from the retentate, this inevitably impedes the flux and transport at the nanoscales. Consequently, these traditional sieving processes are energetically and economically costly. The domain has been boosted subtle nanofluidic transport or the possibilities offered by novel nanoscale materials and in particular great hopes offered by metal-oxide, graphene-oxide and composites.
Our objective is to go beyond develop the concept of active nanofluidic membrane. 'Active' should be understood here as in contrast with the passive state of the art membranes that are based on standard sieving processes. Nanofluidic transport indeed allows going beyond this view and may pave the way to new and more efficient functionalities. In particular, porous materials presenting a large surface charge at the solid-fluid interface can induce an electro-osmotic flow of the fluid under a voltage gradient: when a solution of water and salt fills the submicron pores of the membrane, the charged species reorganize inside the pore in order to screen the chemical charge at the interface. As a consequence, a charge imbalance is created along the radial direction of the pore with an excess of counter-ions with respect to the co-ions. The net charge is then put in movement if a voltage drop is applied between the two sides of the channel and the flow of ions is directly translated in a flow of fluid allowing filtration in function of pore size and nature.
This process presents a major advantage as does not apply a mechanical stress to the membrane allowing the use of fragile and complex materials without the risk of damage.
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