Electronic Supplementary Material (ESI) for RSC Advances.
This journal is © The Royal Society of Chemistry 2015
Supporting information
All glassware were soaked in acid for 24 hours and then washed with excessive tape followed
de-ionized water. Samples were run as triplicates and mean is reported as results in this research
work. The data was computationally processed by using Origin Pro (version 8 SR0) software. To
get neutral pH of processed water, 10 mg/L fluoride solution with 2 gL-1 sorbent was used
otherwise up to 1000 mgL-1 fluoride solution was found stable and can be analyzed on same
quantity of sorbent dose at room temperature where removal was found 161.17 mg/g (fig. 1).
160
140
120
qe (mg/g)
100
80
60
40
20
0
0
200
400
600
800
1000
Initial Fluoride Concentration C0 (mg/L)
Fig 1, Determination of load by MALW at pH 7(+0.2), Room Temperature at various
Fluoride concentration (mg/L) at fixed dose 2g/L
Contact time for 3 different fluoride ion concentrations
The contact time for equilibrium was found to be directly related with concentration of fluoride
and adsorbent dose. It is low for diluted solutions while high for concentrated solutions, 40
minutes for 10, 60 minutes for 20.66 and 95 minutes for 45.45 mgL-1 solutions were observed.
18
16
F ion conc
10mg/L
20.66mg/L
45.45mg/L
qe (mg/g)
14
12
10
8
6
4
0
20
40
60
80
100
time (min)
Fig. 2. Effect of concentration on equilibrium, 2g/L adsorbent dose,, pH 7 ( ±0.2) and room
temperature.
To investigate the chemosorption on heterogeneous surfaces, Elovich model was also applied on
our research studies. The graph of qt against Int has R2=0.954 and value of coefficient α is
93.234 indicating a rapid initial intake of fluoride ion.
4.95
4.90
R2 = 0.954
qt (mg/g)
4.85
4.80
4.75
4.70
4.65
1.5
2.0
2.5
3.0
-1
Int (min )
Fig 3. Elovich model
3.5
(a)
Element
(b)
Wt%
At%
OK
13.97
40.12
MgK
13.49
AlK
Wt%
At%
OK
13.60
40.40
25.50
MgK
12.17
23.79
07.56
12.88
AlK
07.34
12.92
LaL
64.98
21.50
LaL
66.89
22.88
Matrix
Correction
ZAF
Matrix
Correction
ZAF
(c)
Element
(d)
Fig 4. EDS spectra with elemental composition of virgin (a, c) and F– ions sorbed (b, d).
(Conditions: 2g L-1 sorbent dose, equilibrium time 40 min, room temperature, Fluoride
conc. 10 mg L-1 and pH 7.00 (±0.2).