PURIFICATION OF ALUMINUM THROUGH Al2O3 – AlF3 ACTIVE FILTRATION

Filtration is the most cost effective method to purify aluminum. In this paper, filtration experiments have been carried out using both AlF3 slurry coated, and uncoated Al2O3 ceramic foam filter (CFF) to study the removal of both nonmetallic inclusions and impurity elements. The results showed that the 30 ppi CFF removed up to 85% inclusions from aluminum. The contributing mechanisms for the removal of nonmetallic inclusions in the deep bed filtration mode are proposed: (1) collision with walls and interception effect; and (2) the formation of both intermetallic and nonmetallic inclusion bridges during filtration. Fluid dynamics modeling of inclusions attachment to the filter walls showed that most inclusions, especially those with larger sizes, are entrapped at the upper part of the filter while smaller inclusions dispersed well throughout the filter. The active filter could [Mg] remove impurity elements up to 86 %.