INVESTIGATING DISPERSION AND RHEOLOGICAL BEHAVIOR OF IONICALLY STABILIZED AQUEOUS A-ALUMINA SUSPENSION

Dispersion and rheological behaviors of ionically stabilized aqueous alpha aluminasuspensions were investigated in various ph values (3, 11) and solid volume fractions (4, 7, 10,15) vol% using sedimentation experiment as well as viscosity measurement. interface separatingporous-packed sediment from a relatively clear supernatant at ph 11 was measured over 20hours with the aim ofobtaining linearity range, initial settling velocity, final sediment height andsuspension sensitivity factor, whilst it failed to be observed in the case ofph 3 for its turbidsupernatant. thus, the final sediment level instead of interface location was taken intoconsideration. for all solids loading, final sediment level in the case ofph 3 was smaller thanthose in ph 11. the interface was observed to be moving downward in a linear fashion, with thesteady drive toward an equilibrium state, which was substantiated to be ph and solid loadingdependent. as (phi) increased, linearity time changed in an ascending order. ph 11 suspensionsshowed good agreement with the well-known richardson-zaki equation and displayed dramaticvariations in initial settling velocity, whilst it was not the case for ph 3 as understood generally byturbidity observations. in addition, ph and (phi) appeared to be more effective in giving stability tothe suspending systems. on the other hand, rheological behaviors ofthese suspensions were takeninto consideration for better indication of suspension stabilization degree in which suspensionyield stress derived using viscosity values was focused. the results showed that ty at ph 3 is muchlower than that of at ph 11. this is a further indication of hetter dispersion at ph 3. it was alsofound that for all (phi) values, ph 3 suspensions were more stable than the flocculated ph 11 ones.