Interparticle forces, interfacial structure development and agglomeration of gibbsite particles in synthetic Bayer liquors

Surface force, rheological and crystallization techniques have been used to investigate interparticle forces and their link to interfacial structuring and agglomeration of gibbsite crystals in pure, supersaturated sodium and potassium aluminate solutions (synthetic Bayer liquors). Initially repulsiv e interparticle forces exist; these attenuate with time, and are followed b y the emergence and growth of adhesive forces upon further aging. The adhes ive forces were smaller at the gibbsite (001) crystal face compared with ot her faces and their rate of growth greater in sodium aluminate than in pota ssium aluminate solutions over similar aging periods. The rheological data correlated well with the interparticle force determinations. Both the thixo tropic structure and yield stresses increased with time and were greater in sodium-based than in potassium-based liquors. SEM and crystal size analyse s of the crystallized product showed that agglomeration was more pronounced in sodium than in potassium-based Bayer liquors and was more prevalent bet ween non-(001) crystal faces. For the size enlargement of sub-micron sized gibbsite crystals, agglomeration, rather than crystal growth, was the predo minant mechanism and is directly controlled by particle interaction farces. (C) 1999 Elsevier Science Ltd. All rights reserved.