temperature and pressure followed by crystallization of the dissolved material from
the fluid [23]. The water can be replaced by other polar or nonpolar solvents such as
benzene. The combination of microwave and hydrothermal method reported for the
preparation of superparamagnetic iron oxide nanoparticles is advantageous for scaleup and fabrication of uniform particles.
4.2 Ex Situ Methods
Ex situ methods refer to the blending of pre-synthesized nanostructures with polymer using specific techniques such as ball milling, melt blending, and thermal
curing. Unlike in situ methods, it is relatively challenging to handle the nanoparticle
agglomeration due to the high surface energy of nanoparticle in preparing highperformance magnetic particles.
5 Magnetic Separation for Water Purification
Ideal water purification techniques at a low cost have attracted broad interest to be
affordable for developing countries as well. Adsorption technology using an adsorbent satisfies the requirement due to its high performance, ease of operation, and
insensitivity to toxic substances [25]. An optimal adsorbent ought to have the
following characteristics: (1) high performance, (2) fast kinetics, (3) cost-efficient,
(4) environmentally friendly, (5) reusability, and (6) ease of separation to be applied
commercially. The most problematic issue for the removal process is the effectiveness of particle separation from aqueous solution. Water purification process has to
implicate recyclable materials for successive treatment cycles and evade generation
of secondary waste on an industrial scale. Among the adsorbent materials
established, the feasibility of magnetic nano-adsorbents that have a high surfaceto-volume ratio, tunable morphology, and excellent removal performance besides
the magnetism property shows the most promising application for water and wastewater treatment systems. It is anticipated that magnetic separation can emerge to be a
more cost-effective and expedient process for separating tiny powdered particles
than sophisticated membrane filtration.
In the year 1995, magnetic ion exchange resins (MIEX) with the magnetic beads
were introduced for the removal of natural organic matter [26]. Later, the removal of
bromide ion was claimed to varying degrees by using MIEX, but the process was
highly dependent on the alkalinity of the water and concentrations of the competing
ion [27]. The small resin beads with a high surface area allow rapid exchange
kinetics of selective ions, enabling a suitable usage in a continuous process. Agglomeration of the magnetic beads leads to flocculation, which allows higher settling
velocity than for the single particles or fluidization at higher hydraulic loading rates.
10 Removal of Heavy Metal Ions Using Magnetic Materials
403
the fluid [23]. The water can be replaced by other polar or nonpolar solvents such as
benzene. The combination of microwave and hydrothermal method reported for the
preparation of superparamagnetic iron oxide nanoparticles is advantageous for scaleup and fabrication of uniform particles.
4.2 Ex Situ Methods
Ex situ methods refer to the blending of pre-synthesized nanostructures with polymer using specific techniques such as ball milling, melt blending, and thermal
curing. Unlike in situ methods, it is relatively challenging to handle the nanoparticle
agglomeration due to the high surface energy of nanoparticle in preparing highperformance magnetic particles.
5 Magnetic Separation for Water Purification
Ideal water purification techniques at a low cost have attracted broad interest to be
affordable for developing countries as well. Adsorption technology using an adsorbent satisfies the requirement due to its high performance, ease of operation, and
insensitivity to toxic substances [25]. An optimal adsorbent ought to have the
following characteristics: (1) high performance, (2) fast kinetics, (3) cost-efficient,
(4) environmentally friendly, (5) reusability, and (6) ease of separation to be applied
commercially. The most problematic issue for the removal process is the effectiveness of particle separation from aqueous solution. Water purification process has to
implicate recyclable materials for successive treatment cycles and evade generation
of secondary waste on an industrial scale. Among the adsorbent materials
established, the feasibility of magnetic nano-adsorbents that have a high surfaceto-volume ratio, tunable morphology, and excellent removal performance besides
the magnetism property shows the most promising application for water and wastewater treatment systems. It is anticipated that magnetic separation can emerge to be a
more cost-effective and expedient process for separating tiny powdered particles
than sophisticated membrane filtration.
In the year 1995, magnetic ion exchange resins (MIEX) with the magnetic beads
were introduced for the removal of natural organic matter [26]. Later, the removal of
bromide ion was claimed to varying degrees by using MIEX, but the process was
highly dependent on the alkalinity of the water and concentrations of the competing
ion [27]. The small resin beads with a high surface area allow rapid exchange
kinetics of selective ions, enabling a suitable usage in a continuous process. Agglomeration of the magnetic beads leads to flocculation, which allows higher settling
velocity than for the single particles or fluidization at higher hydraulic loading rates.
10 Removal of Heavy Metal Ions Using Magnetic Materials
403