Environmental Engineering Reference
In-Depth Information
Chapter 6
Synthesis, Characterization, and Application
of Magnetic Nanocomposites for the Removal
of Heavy Metals from Industrial Effluents
Zhenghe Xu and Jie Dong
Abstract Magnetic nanocomposites with tailored surface functionalities have
found a wide range of applications, including biological cell separation, waste
remediation, gas purification, and raw material recovery from complex multi-
phase systems. The challenge to magnetic nanocomposite particles for these
applications is to synthesize the particles of strong magnetic properties with
high density of reactive functional groups, diversity of functionalities, and
durability of surface films. In this chapter, the research and development of
magnetic nanocomposite particles for applications to industrial effluent treat-
ment are reviewed. Molecular self-assembly (SA), direct silanation, and meso-
porous silica coating on magnetic particles were developed for the preparation
of magnetic nanocomposites.
In SA, 16-mercaptohexadecanoic acid was anchored onto the g-Fe
2
O
3
surface through chemical bonding between the carboxylic head group of the
surfactant and iron on g-Fe
2
O
3
surface, leaving the thiol or disulfide groups
reactive. In the direct silanation, 3-aminopropyl triethoxy silane (APTES) films
were silanized on bare magnetic particles from toluene and water. To improve
the stability of silanized films, two-step silica-coating method was developed
using sol-gel reaction, followed by dense-liquid silica coating. APTES films
prepared by the silanation on the two-step silica-coated magnetic particles were
found to be more robust than the ones silanized on bare magnetic particles.
Furthermore, an innovative procedure of synthesizing mesoporous silica coat-
ings on magnetic particles was developed to increase specific surface area of
controlled pore sizes. This approach was based on the molecular templating,
followed by sol-gel and templates removal. The resultant products showed a
significant increase in specific surface area and were amenable for functionali-
zation by silanation reaction.
The functionalized magnetic nanocomposites were effective for removal or
recovery of heavy metal ions such as Cu
2+
,Zn
2+
,Ni
2+
,Ag
+
, and Hg
2+
from
