Elucidation of Dynamics in Advanced Separation of Soft Colloid

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In recent years, particle-fluid separation such as filtration, expression, sedimentation and centrifugation is becoming widely accepted in such diversified fields as the biotechnology, biomass industry, functional food, biomedicine, living organism. Therefore, development of advanced separation technology for soft colloids such as microorganism, gel particle, emulsion, biomacromolecule, agglomerated particle, which are deformable and difficult-to-separate particles, is strongly desired.The main purpose of this research is to clarify the dynamics of separation of soft colloids. Filtration, expression, sedimentation and centrifugation were conducted using microorganism, hydrogel, emulsion as test sample. We have ascertained separation behaviors, deformation characteristic of particles and the properties of gelatinous aggregates of particles (cake and sediment) which had a significant influence on separating function. It was revealed that the filter cake and sediment composed of soft colloids have extremely high compressibility. It was also shown that the cake and sediment of soft colloids exhibited the porosity which was less than hexagonal close packing of undistorted spheres because of the deformation of the soft particles under the action of the solid compressive pressure. Consequently, it is preferred that separation of soft colloids is conducted under the relatively low pressure since the increase in the pressure does not necessarily lead to the improvement of the separation properties. These findings provide a valuable information for design of optimum operation and development of novel separation technology, and will be greatly contributed to advancement of diverse fields associated with separation of soft colloids.