Procédés de séparation membranaire pour la production en continu de nanocristaux de polysaccharides : approche expérimentale et modélisation

Abstract : The current work investigates the use of cross flow microfiltration using ceramic membrane to fractionate the heterogeneous suspension obtained after starch hydrolysis in order to isolate starch nanocrystals. The final aim is to evaluate the possibility of coupling the filtration step to the hydrolysis step in a single production loop in order to enhance the starch nanocrystal production yield. The characterizations of the suspension (particle size and charge) obtained with the classic production process indicates that it was a mixture of starch nanocrystal aggregates and starch residues, individualized starch nanocrystals represent only 5 % of the initial starch. The fractionation study was done using two pilot plans, in a dead end configuration at laboratory scale (plate membrane) and in a cross flow configuration at semi-industrial scale (tubular membrane). Design of experiments methodology was used to optimize the fractionation efficiency when filtering a neutral suspension considering the effect of filtration parameter on the transmission yield and membrane fouling. In the optimized condition, it was possible to recover 25 % of starch nanocrystals while keeping the permeate flux at its highest value. Mean diameter of the recovered particle was less than 300 nm. At this condition, it was also possible to recover the starch nanocrystals directly from the acidic mixture obtained at the end of the hydrolysis step. The analysis of fouling mechanism using dead end filtration experiments highlights that membrane fouling occurs because a cake bult up at the membrane surface. This study investigates also the use of ceramic ultrafiltration membrane in a diafiltration process in order to purify the acidic suspension from soluble molecules without modifying particle size distribution which is a promising technique for a large scale production.
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Ahlem Romdhane. Procédés de séparation membranaire pour la production en continu de nanocristaux de polysaccharides : approche expérimentale et modélisation. Génie des procédés. Université de Grenoble, 2014. Français. ⟨NNT : 2014GRENI074⟩. ⟨tel-01153860⟩

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