Viscoelastic properties of flocculated alumina suspensions during pressure filtration

The relation of applied pressure–height of piston during pressure filtration was measured for aqueous 7 vol % suspensions of positively charged 150 nm alumina particles at 0.2 mm/min of crosshead speed of piston. Application of alternating current field in the frequency range from 0.01 to 1000 Hz at 10 V accelerated the colloidal phase transition from dispersed to flocculated suspension, and decreased the consolidation pressure. The characteristics of the flocculated suspension with decreasing suspension height was analyzed based on the viscoelastic models (Maxwell and Voigt models). The flocculated suspension behaved as a liquid like at a low particle concentration in both the models. The applied pressure was related to the product of viscosity of liquid element and crosshead speed of Voigt model. The influence of solid element of Voigt model became stronger with decreasing suspension height (increasing solid content of the flocculated suspension). The applied pressure was proportional to the Young’s modulus of solid element in the final region of filtration.