Starting: September 2014
Vegetal biomass is a plentiful and renewable resource that is looked at as a future raw material for the production of many “green” products, chemicals and materials according to the concept of biorefinery. The separation of the main constituents extracted from biomass is one of the key steps of biomass processing and in this field, pressure driven membrane separation processes such as ultrafiltration are considered as promising solutions. However, the development of these techniques encounters the problem of membrane clogging that dramatically limits their efficiency.
Recent studies have demonstrated that ultrasounds had the ability of reducing membrane fouling and could therefore improve transmembrane fluxes.
This project focuses on the understanding of the mechanisms involved during an ultrasound assisted cross-flow membrane separation process, with the purpose of developing this innovative technique for applications in biorefinery.
An experimental cross-flow ultrafiltration system has been designed to study the behaviour of different colloidal suspensions (microfibrillated cellulose, cellulose nanocrystals and model clay dispersions) under the combined effects of ultrasound waves, shear flow, and pressure (image below)
In order to correlate the evolution of the concentration profiles of the layer near the membrane surface (a few hundred microns thick) to the flow fields, a multi-scale approach is developed, combining measurements at both the nanometric (1) and the micrometric (2) length scales.
Structural organisation of cellulose nanocristals near the membrane surface during ultrafiltration process and 2D SAXS
patterns at different distances z to the membrane surface (from left to right : z= 20, 60, 120, 160, 200, 300, 500, 700 µm)
The understanding of the phenomena induced by ultrasound waves on the particles aggregation is expected to contribute to the optimization of a new ultrasound assisted membrane separation process.
This project involves a collaboration between LRP and LGP2 laboratories.
(1) Small Angle X-ray Scattering – SAXS
(2) Particle Image Velocimetry - PIV