Characterization and application of silicon carbide (SiC) membranes to oenology

Abstract

After fermentations, the crude wine is a turbid medium not accepted by the consumer therefore, it needs to be filtered. Wine is increasingly filtered on microfiltration membranes but the low porosity of membranes currently used limits the efficiency of industrial installations. In fact, an increase in flow rates is expected in order to reduce the number of cleaning cycles and the size of the installations. 

SiC membranes have very interesting physico-chemical characteristics: low density, high porosity, high hydrophobicity, and good resistance to extreme pH and can become a solution to the problems encountered in the oenology sector. In order to apply these membranes, it’s essential to know their microstructure to understand their physico-chimic and hydrodynamic properties. To provide relevant information, different analytical techniques such as 2D, 3D imaging, porosity by mercury intrusion and measurement of contact angle were used. Poral phase analysis of membranes obtained has given concurrent results for all analytical techniques used and with the data provided by the membrane manufacturer. Compared to other ceramic membranes used in oenology, SiC membranes are anisotropic, have a higher porosity (> 40 %) and have a lesser tortuosity (1.20) giving them higher permeate flows. 

They also have a high hydrophobicity (water = 85.5°) explaining their better resistance to organic adsorption. Due the fact that wine is a complex and fouling colloidal matrix, filtration tests have been carried out on wine in order to identify the best filtration operating conditions. For a turbulent flow regime and a transmembrane pressure around 2 bars, a high permeate flux was obtained (450 l.h-1.m-2.bar-1) and this flux is permeat flux dependant. 

Finally, SiC membranes regeneration was studied: due to an organic fouling found after the filtration sessions, a sodium hydroxide clean-in-place combined with surfactants and hydrogen peroxide at high temperature allowed to recover the total permeability of the membranes.