The influence of interfacial structuring on gibbsite interactions in synthetic Bayer liquors

The interaction forces between gibbsite particles aging in synthetic, super saturated sodium and potassium aluminate solutions (Bayer liquors) have bee n investigated. Compliance with DLVO-type behavior was observed in dilute e lectrolyte. Under synthetic Bayer conditions, non-DLVO, repulsive steric fo rces exist. Upon aging, this steric repulsion gradually diminishes and disa ppears. A structured interfacial layer, displaying inner and outer regions of different compressibility, develops as aging occurs and interparticle ad hesion increases. At high particle approach velocities, hydrodynamic forces exist which are dependent upon the viscosity of solution. The steric, adhe sive, and hydrodynamic interactions are all greater in NaAl(OH)(4) compared with KAl(OH)(4) liquors of the same concentrations and degree of aging. So lution AI(OH)(4)(-) ion-mediated interfacial structuring is apparently resp onsible for the time-dependent repulsive and adhesive forces. These interfa cial phenomena are perceived to be precursors to, or part of, gibbsite crys tal growth and agglomeration mechanisms. (C) 1999 Academic Press.