Environmental Engineering Reference
In-Depth Information
reduction in curvature of surfactant aggregates. Such change may be achieved by
altering the surfactant chain length, introducing twin chains, adding electrolytes,
or by addition of polar and non-polar organic additives. Addition of short-chain
alcohols as co-surfactants can also be used to alter the packing parameter, result-
ing in elongated micelles. Furthermore, addition of short-chain amine co-surfac-
tants can decrease the pore size of the inorganic structures. By controlling the
packing parameter of different surfactants, mesoporous materials of different
structures have been synthesized [115, 116, 117, 118, 119]. Detailed descriptions
of reaction variables are available in many monographs [109, 110, 120, 121].
Synthesis Process Monitored by Zeta-Potential Measurement
To confirm the role of each step in the proposed synthesis process, the zeta-
potential distributions of bare magnetite (Fe
3
O
4
) (step I in Fig. 6.7 previous),
dense-liquid silica (DLS) coated magnetite (step II in Fig. 6.7 previous),
templated DLS magnetite (step III), sol-gel coated particles with templates
(step IV), and the particles after calcination (step V) were measured over a
wide pH range and the results are shown in Fig. 6.10.
The IEP of the bare magnetite is at pH 6.8, which is close to the value of
mineral magnetite. After DLS coating, the IEP of the coated particles was
found at pH 2.0, which is same as the IEP for mineral or fused silica. This silica
Fig. 6.10 Zeta potentials of different particles: (1) bare magnetite particles; (2) DLS coated
magnetite particles; (3) templated DLS magnetite (4) sol-gel coated particles with templates;
and (5) particles after calcination
