Environmental Engineering Reference
In-Depth Information
OH
Montmorillonite
or
Hectorite
EtO
Montmorillonite
or
Hectorite
OH
OH
+
Si
NH
2
NH
2
O
EtO
OEt
Montmorillonite-NH
2
or
Hectorite-NH
2
Br
EtO
S
S
S
O
O
S
Montmorillonite
or
Hectorite
NH
Montmorillonite
or
Hectorite
Br
NH
2
H
2
N
H
H
H
2
N
AEPE-Montmorillonite or
AEPE-Hectorite
Montmorillonite-NH-Br or
Hectorite-NH-Br
figure 16.9
grafting of montmorillonite (mmT) and hectorite (Hect.) with 2-(3-(2-aminoethylthio)propylthio)ethanamine (AePe).
Tannin-immobilized activated clay
The adsorption of anionic species of partly Cr
6+
OH
Activated clay
R
Tannin
O
O
R
HO
OH
OH
HO
Cr
Al
R
O
OH
O
HO
Al
O
+
OH
O
HO
Si
O
HO
(a)
+
Si
HO
Cr
HO
OH
OH
Al
O
OH
HO
OH
-
O
Si
O
HO
OH
HO
OH
OH
OH
R
OH
+
OH
H
+
R
Cr
6+
Cr
3+
(b)
O
R
Cr
+
O
HO
Al
O
OH
Si
HO
HO
OH
O
Cr
+
O
R
The adsorption of reduced Cr
3+
ions
figure 16.10
Adsorption mechanism of total Cr (TCr) onto tannin-immobilized activated clay (TA-AC).
novel organo-clay minerals AePe-mmT and AePe-Hect. were synthesized by grafting AePe onto the clay minerals
(fig. 16.9) [80]. The xRd patterns indicated that the chelating agents (AePe) were mainly grafted on the external surface of
mmT, while AePe was grafted on both the external and interlayer surfaces of Hect. The AePe-modified clay minerals were
good chelating materials for Hg(II) ions, compared to the unmodified clay minerals. The adsorption capacity for Hg(II) of
AePe-mmT and AePe-Hect. was 46.1 and 54.7 mg/g, respectively, for solution containing 140 mg/l Hg(II) ions (pH 4).
Tannin-immobilized activated clay (TA-AC) as a spent adsorbent was used to remove Cr(VI) ions from the aqueous solution
(fig. 16.10) [81]. The maximum adsorption capacity was 24.09 mg/g from the Langmuir isotherm model at 330 K with initial pH = 2.5.
Oxidation-reduction was found to occur during the adsorption process. It enhanced the removal capability by partly reducing Cr(VI)
ions to Cr(III) ions. so TA-AC demonstrated a high adsorption capacity for Cr(VI) comparable to other adsorbents.
