fields. Therefore, the contribution of diamagnetism is insignificant unless it is the
only magnetism present. Materials such as acetone, alumina, carbon dioxide, copper,
lead, quartz, silver, and water are diamagnetic.
3.2 Paramagnetism
Paramagnetism results from the magnetic forces on unpaired electrons. In paramagnetic materials, some of the atoms or ions have a net magnetic moment due to
unpaired electrons in partially filled orbitals [15]. Under the influence of an applied
field, there is a partial alignment of the atomic magnetic moments parallel to the
direction of the field, resulting in a net positive magnetization and positive susceptibility lies between 10
À3 and 10
À5 . The net magnetization of the atom is small due
to random ordering of moments but more significant than the diamagnetic contribution. Similar to diamagnetism, the magnetization is zero when the field is removed.
Materials such as clay, carbonate, silicate, sodium, and platinum are paramagnetic.
3.3 Ferromagnetism
Ferromagnetism occurs when there are exchange interactions among the electrons in
the material. In ferromagnetic materials, the atomic magnetic moments align parallel
or antiparallel to each other due to an interaction between neighboring moments or
mutual reinforcement of the dipoles. Unlike paramagnetic materials, the atomic
moments in these materials exhibit powerful exchange forces, equivalent to a field
on the order of 1000 Tesla or around 100 million times the strength of the earth’s
field [16]. The parallel alignment of moments results in large net magnetization even
in the absence of a magnetic field, giving high susceptibility approaching 10
6 . Above
the Curie temperature, ferromagnetic materials exhibit paramagnetic behavior. Iron,
nickel, and cobalt and many of their alloys are typical ferromagnetic materials.
3.4 Antiferromagnetism
Antiferromagnetism occurs when the magnetic moments produced in neighboring
atoms line up in opposition to one another in the magnetic field. This magnetic
ordering cancels out the magnetic moments, and net magnetization is zero. The
magnetic susceptibility is positive and small, approximately 10
À5 to 10
À3 . Moreover, these materials exhibit paramagnetic behavior like ferromagnetic materials
above a transition temperature, Néel temperature [17]. Cobalt oxide, chromium,
manganese chloride, manganese oxide, and nickel oxide are examples of
10 Removal of Heavy Metal Ions Using Magnetic Materials
399
only magnetism present. Materials such as acetone, alumina, carbon dioxide, copper,
lead, quartz, silver, and water are diamagnetic.
3.2 Paramagnetism
Paramagnetism results from the magnetic forces on unpaired electrons. In paramagnetic materials, some of the atoms or ions have a net magnetic moment due to
unpaired electrons in partially filled orbitals [15]. Under the influence of an applied
field, there is a partial alignment of the atomic magnetic moments parallel to the
direction of the field, resulting in a net positive magnetization and positive susceptibility lies between 10
À3 and 10
À5 . The net magnetization of the atom is small due
to random ordering of moments but more significant than the diamagnetic contribution. Similar to diamagnetism, the magnetization is zero when the field is removed.
Materials such as clay, carbonate, silicate, sodium, and platinum are paramagnetic.
3.3 Ferromagnetism
Ferromagnetism occurs when there are exchange interactions among the electrons in
the material. In ferromagnetic materials, the atomic magnetic moments align parallel
or antiparallel to each other due to an interaction between neighboring moments or
mutual reinforcement of the dipoles. Unlike paramagnetic materials, the atomic
moments in these materials exhibit powerful exchange forces, equivalent to a field
on the order of 1000 Tesla or around 100 million times the strength of the earth’s
field [16]. The parallel alignment of moments results in large net magnetization even
in the absence of a magnetic field, giving high susceptibility approaching 10
6 . Above
the Curie temperature, ferromagnetic materials exhibit paramagnetic behavior. Iron,
nickel, and cobalt and many of their alloys are typical ferromagnetic materials.
3.4 Antiferromagnetism
Antiferromagnetism occurs when the magnetic moments produced in neighboring
atoms line up in opposition to one another in the magnetic field. This magnetic
ordering cancels out the magnetic moments, and net magnetization is zero. The
magnetic susceptibility is positive and small, approximately 10
À5 to 10
À3 . Moreover, these materials exhibit paramagnetic behavior like ferromagnetic materials
above a transition temperature, Néel temperature [17]. Cobalt oxide, chromium,
manganese chloride, manganese oxide, and nickel oxide are examples of
10 Removal of Heavy Metal Ions Using Magnetic Materials
399