Stirred bead mill grinding of gibbsite:surface and morphological changes

Abstract

This paper describes the structural and surface changes in gibbsite subjected to mechanical activation using stirred media mill. During milling, the median particle size decreased from 52 gm to —3 gm in 30 min indicating high milling efficiency. SEM studies revealed that gibb-site particles, present in the feed as agglomerates of pseudohexagonal platelets, ruptured by attrition at grain joints followed by chipping leading to further frag- mentation. During milling, progressive decrease in the intensity of (002) peak of gibbsite in powder X-ray diff-raction pattern indicated amorphisation. It was found that the presence of hematite favoured amorphisation of gibb-site. Zeta potential and iso-electric point of gibbsite changed during milling which is indicative of alteration of gibbsite surface.