Magnetic Separation of Metal Ions

The magnetic separation was investigated for Co 2 + (9500 x 10 - 6 cm 3 mol - 1 ) and Fe 3 + (14600 x 10 - 6 cm 3 mol - 1 ) ions and for Cr 3 + (6200 x 10 - 6 cm 3 mol - 1 ) and Al 3 + (-2 x 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 x 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.