Environmental Engineering Reference
In-Depth Information
Nano-IPFs, or simpliied as “nanolocculants,” are deined as inorganic compounds
with particle size distribution (PSD) in the nanoscale. The nano-IPF as a new kind of
species can be prepared by special physicochemical processes and under certain separa-
tion and puriication. In industrial production, the nano-Al
13
coagulant is deined as an
IPF-PACl containing Al
13
species >70% as a component. Since the particle size is quite
small, i.e., between molecular and colloidal scale, nano-Al
13
coagulants exhibit special
physicochemical properties and can be tailor-made to it the application demanded and
to meet a certain PSD (the PSD effect of IPF is also addressed in this chapter). Thus, the
nano-IPFs could be considered further as the third generation of coagulants. The rela-
tive theory and application will contribute certainly to the science and technology of
coagulation.
38.2 Loss of Al
13
in High-Concentration PACl
Since Al
13
is only one of the hydrolysis products of Al(III), pH becomes a signiicant factor
for the stability and distribution of Al
13
. When the concentration of PACl is increased, the
spontaneous hydrolysis becomes more signiicant. In many experiments, it is indicated
that Al
13
could not exist in high-concentration PACl solutions with >2.0 mol Al/L (Huang
et al., 2006a,b; Kloprogge et al., 1992; Zhao et al., 2013). As shown in Figure 38.1, the content
of Al
13
changes obviously with pH in PACl of 0.01, 0.1, 0.5, and 2.0 mol Al/L. A pH zone
can be observed at 3.5-5.0. Below pH 3.5, no Al
13
can be observed in the PACl solution.
Therefore, how to prepare a commercial PACl with a high concentration of Al
13
is a big
challenge.
90
0.01 mol/L
80
0.1 mol/L
0.5 mol/L
70
2.0 mol/L
60
50
40
30
20
10
0
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
pH
FIGURE 38.1
Change of Al
13
and pH in PACl solution. (From Huang, L. et al.,
J. Environ. Sci
. 18, 872, 2006a.)
