Reclamation of Waste Kaolin in Palm Oil Mill

Abstract

Kaolin slurry with specific gravity of 1.12-1.14 is normally used for separation of palm kernel and palm shell in palm oil milling process. Oil and other contaminants occurred during the separation were anticipated to affect on the specific gravity of kaolin, thus decreased the separation capability. Consequently, new batch of virgin slurry is needed.?? To reduce the kaolin cost, a method to reclaim the spent kaolin is needed. In laboratory study, treatment by hot water (50, 70, 90 and 100^oC) and by alkaline (1% NaOH) (0.5, 1.0, 2.0 and 2.5 M). It was found that treatment by hot water at 100^oC and 1% NaOH of 2.5 M, the spent kaolin regained its specific gravity at 1.50 and 2.59, respectively. Therefore, the reclaimed kaolin had the specific gravity equal to that of the virgin kaolin (2.6). There is no significant difference in the range of NaOH concentrations tested, thus the 1.5 M NaOH was selected for the industrial application. The reclaimed kaolin had the specific gravity of 2.57 while its slurry had the specific gravity of 1.14. It could separate 95% of palm kernel with only 1.5% palm shell contaminated. Comparison of the composition of reclaimed kaolin and virgin kaolin revealed that their composition were slightly difference in some major components. The percentage of Al₂O₃ and SiO₂, were decreased while that of K₂O and CaO were increased. Economic analysis indicated an attractive return worth for kaolin reconditioning investment.