Amazonian Kaolin Purification by Selective Flocculation

C.H. Sampaio*, F. Larroyd, C.O. Petter, W. Aliaga

Mineral Processing Laboratory, Center of Technology, Federal University of Rio Grande do Sul, P.O. box 15021, ZIP 91501-970, Porto Alegre, Brazil.


Received 26 April 2002; accepted 15 June 2003



ABSTRACT

The most important kaolin deposit in the north of Brazil presents titaniferous contaminants finely disseminated in the bulk. Those contaminants affect the commercial value of the mineral urging a process for removing them. The removal of those contaminants can not be carried out by conventional techniques, due to the ultra-fine size of the minerals.
This paper presents a mineral concentration process based on selective adsorption of soluble polymers. Flocks of considerable sizes and quite consistent are generated by interactions between anionic polyacrylamide molecules and titaniferous minerals which can be separated from a kaolin suspension by sedimentation.
The best results were obtained after a polymer, having a weak anionic charge (10%), was used as flocculant for kaolin impurities. The mineral was dispersed in aqueous media using a high concentration of sodium hexamethaphosphate (4.8 Kg/t) at a pH value around 10. In these conditions, the content of TiO₂ in the sample was reduced from 1.39% to less than 0.5% and kaolin recoveries ranged between 50 and 65%. Sedimentation of the flocks reached rates around 5.2 mm/min.


Keywords: Kaolin; Selective flocculation; TiO₂



* Corresponding author
   E-mail : sampaio@ct.ufrgs.br