Environmental Engineering Reference
In-Depth Information
magnetite [18], the adsorption of organic dyes by poly(oxy-2,6-dimethyl-1,
4-phenylene) [19], removal of an azo-dye, acid red B (ARB) from water by
MnO-Fe
2
O
3
composites as adsorbent-catalyst materials [20], oil spill remedia-
tion by polymer-coated magnetic particles [21], and removal of heavy toxic
metals and purification of the hazardous waste waters by magnetic filtration/
sorption technology [22, 23, 24]. In addition, magnetic nanoparticles with
appropriate surface coatings have found various biomedical applications, as
contrast agents in MRI (magnetic resonance imaging), colloidal mediators
for cancer magnetic hyperthermia, and active constituents of drug-delivery
platforms, as well as for tissue repair, cell and tissue targeting, and transfection
[25, 26, 27, 28].
For selective recovery or removal of heavy metals from voluminous indus-
trial effluents with suspended solids, the use of MCS is of particular importance,
as the technique combines the advantages of technical feasibility and flexibility
with economic value and environmental acceptability. A schematic illustration
of MCS is shown in Fig. 6.1 [29]. In this figure, magnetic composite particles are
added to a hydrometallurgical processing suspension that contains precious
metal ions and many other waste solid particulates. The precious metal ions
selectively adsorb on the added magnetic composite particles through molecu-
lar recognition by surface functional groups. Along with the magnetic particles,
the adsorbed metal ions are separated from the suspension by an external
magnetic field. The metal ions loaded on the isolated magnetic particles can
be stripped off by, for example, acid washing, and the particles can then be
reused. Precious metals can, on the other hand, be produced from the concen-
trated ion solution by precipitation, crystallization, and/or electrowinning.
Fig. 6.1 Illustration of magnetic separation technology in metal recovery from an industrial
effluent
