Environmental Engineering Reference
In-Depth Information
ofthesaltsrespectivelyin1Lofdistilledwater.ForAs(III)stocksolution,NaAsO
2
wasirstdehydratedbydryingat105°Cfor4h.ThepHoftheaqueoussolutionsof
F
-
-andAs(III)aspreparedwas6.50±0.05and5.70±0.05respectively.Thework-
ing solutions for adsorption experiments were freshly prepared by diluting the stock
solution (1,000 mg/L).
Preparation of Adsorbent
Waste bamboo dust was collected from Nagaon Paper Mill. The material was thor-
oughly washed to get rid of the dyes and pigments, and other soluble impurities,
oven dried, ground, and sieved to get the fraction between mesh size 50 and 100.
The materials were modified by treating with 0.5 N HCl, HNO
3
and H
2
SO
4
for 5 h.
After modification, they were again washed with distilled water to remove the
excess acid. In total, four adsorbents, namely, raw bamboo dust (B1), 0.5 N HCl
treated bamboo dust (B2), 0.5 N HNO
3
treated bamboo dust (B3) and 0.5 N H
2
SO
4
treatedbamboodust(B4)wereprepared.
Surface Area Determination
The surface area measurement was based on adsorption of the dye, Methylene Blue,
on the adsorbent (Hang and Brindley
1970
; Percival and Lindsay
1997
). In this
method, the material was exposed to progressively increasing concentrations of
MethyleneBluesolution(25,30,40,50,60and70mg/L)undercontinuousagita-
tion and kept for 6 h in contact with the dye solution. The amount of dye adsorbed
on unit mass of the adsorbent at equilibrium (
q
e
mg/g) was obtained from the amount
of dye remaining unadsorbed (
C
e
mg/L) measured spectrophotometrically for each
dye concentration. The amount of dye required to form a complete monolayer (
q
m
)
was computed from Langmuir isotherm,
=
(
)
+
(
)
Cq
/
1
/
bq
1
/
q C
(1)
ee
m
m
e
where the slope of the plot of
C
e
/
q
e
vs.
C
e
gives the Langmuir Monolayer Capacity,
q
m
. The specific surface area (
s
g
) of the adsorbent was obtained from the relation,
sMAN
g
=××
(2)
f mA
where
M
f
is number of milliequivalents of Methylene Blue adsorbed per 100 g of
material,
A
m
= surface area of the Methylene Blue molecule (1.30 × 10
−18
m
2
/
molecule), and
N
A
is Avogadro Number (=6.023×10
20
molecules per
milliequivalent).
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