Cake filtration of viscoelastic gel particles

• Main Authors: Chung-ping Shih, 史頌平
• Other Authors: Wei-ming Lu
• Format: Others
• Language: en_US
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/47307554614272013270

碩士 === 國立臺灣大學 === 化學工程學研究所 === 88 === The swelling behavior of hydrogel particles results from a balance between two forces. Swelling is due to the osmotic pressure of the free counterions and the electrostatic intrachain repulsion. These forces are counterions balanced by the elastic response of the cross-linked polymer network. This study has investigated the filtration behavior of viscoelastic hydrogel particles as well as the deformability. The difference of the deformability between the incompressible gel particles and swollen gel particles has also been studied. A linear viscoelastic model (Kelvin model) has been used to describe the time-independent deformation behaviors of swollen gel particles. In addition, a surface contact model of swollen gel particles has been proposed by relating the volumetric change of the particle to its strain. The results agree well with the theoretical estimation. The experimental results have showed that the lateral expansion of the swollen gel particle due to compression was less than that of the incompressible gel particle. As the volume of the swollen particle continuously decreased due to the migration of the liquid inside the polymer network of swollen particle migrated under compression. Constant pressure filtration tests of rigid particles (polystyrene), incompressible gel particles (Ca-alginate), and swollen gel particles (Sephadex G50S) have been conducted. The filtration results have showed that the filtration resistance of incompressible gel particles was larger than swollen particles. It was possibly because the liquid of inside the Sephadex particles would migrate from the matrix under compression; however, Ca-alginate particles, like all other incompressible particles, remain their volume unchanged during the loading process. As a result, when a incompressible gel bead was highly compressed, it become pretty flat and therefore occupied more void space in the bottom layer of the cake than a swollen gel particle. Hence the filtration of the incompressible particles Ca-alginate was more difficult to conduct than the swollen particles Sephadex G50S.