Rheological investigations of gibbsite particles in synthetic Bayer liquors

Rheological studies of colloidal gibbsite suspensions in caustic aluminate solutions (synthetic Bayer liquors) were undertaken to elucidate the partic le interaction behaviour during the crystallisation step of Bayer processin g. The influence of suspended particle volume fraction: temperature and alu minate supersaturation on both the static and dynamic rheology and its time -dependency is reported. Freshly prepared suspensions are near Newtonian, b ut upon aging, exhibit increased apparent viscosities, pseudoplasticity, yi eld stresses, viscoelasticity and thixotropy. The highly shear sensitive gi bbsite particle networks which form in supersaturated liquors are not obser ved in saturated or under-saturated aluminate solutions. The rate of struct ure formation has been shown to depend strongly on the initial degree of su persaturation, but only weakly on temperature. These findings reflect the c ondition-dependent particle interaction behaviour which is influential in c ontrolling the flocculation and cementation steps of gibbsite agglomeration . (C) 1999 Elsevier Science B.V. All rights reserved.