Magnetic Separation of Metal Ions

The magnetic separation was investigated for Co 2+ (9500 × 10 -6 cm 3 mol -1 ) and Fe 3+ (14600 × 10 -6 cm 3 mol -1 ) ions and for Cr 3+ (6200 × 10 -6 cm 3 mol -1 ) and Al 3+ (−2 × 10 -6 cm 3 mol -1 ) ions. The metal ion solutions were spotted on a silica gel support, and exposed to a magnetic field of 410 kOe 2 cm -1 intensity × gradient. The Co 2+ ions move farther toward the maximum field than the Fe 3+ ions. The result is explained by the fact that the Fe 3+ ions are adsorbed more strongly on the silica gel surface than the Co 2+ ions. The Cr 3+ ions move farther toward the field center than the Al 3+ ions. This occurs because the Cr 3+ ions are attracted more strongly by the magnetic force than the Al 3+ ions. It is demonstrated that the separation makes effective use of the adsorption activities as well as the magnetic susceptibilities.