Environmental Engineering Reference
In-Depth Information
0.1 M FeSO
2
.
7H
2
O + 0.2 M Al
2
(SO
4
)
3
.
12H
2
O + 0.1 M Ce(SO
4
)
2
.
4H
2
O
+
Cross linked
PVA
+
Dissolved PVA
Fe-Al-Ce entrapped in PVA matrix
H
2
O
+
PVA
FIGURE 19.6
Schematic of steps employed during extrusion of FAC-PVA composite. (Adapted from B. Zhao, Y. Zhang,
X. Doub, X. Wu, and M. Yanga,
Chem. Eng. J.
, 185, 211, 2012.)
optimized by varying the amount of FAC and the binder. The optimum conditions
proposed are as follows: binder/FAC powder ratio, 1.4; average cylinder diameter of
granules, 1.6 mm; drying temperature, 65°C. The granulated composite exhibited a
Langmuir maximum adsorption capacity of 51.3 mg/g at pH 7.0 ± 0.2.
19.4.2.3 Inorganic Metal Oxide as Support Matrix
Chen et al. [114] developed a granulation technology for coating nanoscale FAC onto a
cheap inorganic support, sand. For this, an acrylic styrene copolymer latex mixed with
FAC was spray-coated onto the sand surface in a luidized bed. Using the latex as a binder
improved the stability of the coated layer. The granules had spherical shape with size vary-
ing from 2 to 3 mm. For the optimal stability and adsorption capacity, a coating amount of
27.5% was suggested. At optimum conditions, the luoride uptake capacity of the material
was found to be 2.22 mg/g (pH 7.0; initial luoride concentration of 0.001 M). An inverse
relation was observed between the coating thickness and the stability of the granules; that
is, the higher the coating thickness, the lower the stability of the granules. However, luo-
ride uptake capacity increased with increasing coating thickness. On the basis of the FT-IR
data, the reduction in adsorption capacity was attributed to the interaction between the
latex surface with the active hydroxyl on the FAC adsorbent. A similar coating producer
was used by the same group to support FAC onto glass beads [115]. The adsorbent was
used in a packed bed for deluoridation of water. They found a direct relation between the
coating temperature and the degree of cross-linking of the polymer and the associated
mechanical strength of the granules. The optimal parameter conditions arrived at are as
