SELECTIVE FLOCCULATION OF ULTRAFINE IRON-ORE .2. MECHANISM OF SELECTIVE FLOCCULATION

The mechanisms involved in the selective flocculation of hematite from kaolinite, using starch as the flocculant, have been investigated. Ad sorption isotherms of starch on hematite and kaolinite were measured b y a thermogravimetric method, supported by infrared analysis of the ad sorbed species and zeta-potential changes on adsorption of starch. The preferential adsorption of starch onto hematite was proposed to be du e to the higher concentration of hydroxylated metal adsorption sites. By comparing selective flocculation performance with adsorption result s, it was established that flocculation occurs by the classical bridgi ng mechanism.