Table 1. Experimental ranges and levels of the effective factors.
Coded values (Xi)
|
pH
|
m (mg)
|
CTO (mgL-1)
|
CBB (mgL-1)
|
-2
|
4
|
2.5
|
25
|
0
|
-1
|
6
|
10
|
100
|
100
|
0
|
8
|
17.5
|
175
|
200
|
1
|
10
|
25
|
250
|
300
|
+2
|
12
|
32.5
|
325
|
400
|
Table 2. Central-Composite design matrix and obtained response results (%R).
Std Order
|
pH
|
m
|
CTO
|
CBB
|
%RTO
|
%RBB
|
1
|
6
|
10
|
100
|
100
|
19
|
10
|
2
|
10
|
10
|
100
|
100
|
61.4
|
46.6
|
3
|
6
|
25
|
100
|
100
|
39.2
|
25.7
|
4
|
10
|
25
|
100
|
100
|
92.1
|
80
|
5
|
6
|
10
|
250
|
100
|
12.5
|
4.0
|
6
|
10
|
10
|
250
|
100
|
46.8
|
35.1
|
7
|
6
|
25
|
250
|
100
|
30.3
|
21.3
|
8
|
10
|
25
|
250
|
100
|
74.5
|
68.5
|
9
|
6
|
10
|
100
|
300
|
13.3
|
13.9
|
10
|
10
|
10
|
100
|
300
|
55
|
48
|
11
|
6
|
25
|
100
|
300
|
35.2
|
35.3
|
12
|
10
|
25
|
100
|
300
|
87.8
|
83.9
|
13
|
6
|
10
|
250
|
300
|
7
|
10.5
|
14
|
10
|
10
|
250
|
300
|
40.5
|
38.1
|
15
|
6
|
25
|
250
|
300
|
26.6
|
32.9
|
16
|
10
|
25
|
250
|
300
|
70.5
|
75.9
|
17
|
4
|
17.5
|
175
|
200
|
2
|
5.5
|
18
|
12
|
17.5
|
175
|
200
|
83
|
86.9
|
19
|
8
|
2.5
|
175
|
200
|
10
|
18.4
|
20
|
8
|
32.5
|
175
|
200
|
60
|
74
|
21
|
8
|
17.5
|
25
|
200
|
73
|
62.2
|
22
|
8
|
17.5
|
325
|
200
|
49
|
48.1
|
23
|
8
|
17.5
|
175
|
0
|
46
|
0
|
24
|
8
|
17.5
|
175
|
400
|
35
|
16
|
25
|
8
|
17.5
|
175
|
200
|
31
|
36
|
26
|
8
|
17.5
|
175
|
200
|
32
|
36
|
27
|
8
|
17.5
|
175
|
200
|
31
|
36
|
28
|
8
|
17.5
|
175
|
200
|
31
|
37
|
29
|
8
|
17.5
|
175
|
200
|
32
|
37
|
30
|
8
|
17.5
|
175
|
200
|
32
|
36
|
31
|
8
|
17.5
|
175
|
200
|
31
|
37
|
Table 3. Determination of BB and TO in standard solutions by obtaining equations in the binary system.
Initial concentration of binary mixture (mg L-1)
|
Found (mg L-1)
|
Found
(mg L-1)
|
Recovery %
|
Recovery %
|
TO
|
BB
|
TO
|
BB
|
TOa
|
BBa
|
13
|
3
|
12.4
|
3.1
|
95.3± 0.3
|
103.3±0.2
|
10
|
6
|
10.2
|
5.8
|
102.0±0.2
|
96.6±0.1
|
9
|
15
|
8.8
|
15.3
|
97.7±0.3
|
102.0±0.4
|
11
|
1
|
11.4
|
17.3
|
103.6±0.3
|
101.7±0.2
|
2
|
13
|
2.1
|
12.9
|
105.0±0.1
|
99.2±0.3
|
a: 3 repetitions in the measurement.
Tabe.4. Analysis of Variance (ANOVA) for the suggested models
Source ( TO)
|
DF
|
Adj SS
|
Adj MS
|
F-Value
|
P-Value
|
Model
|
14
|
17393.7
|
1242.4
|
1618.32
|
0.000
|
Linear
|
4
|
15502.4
|
3875.6
|
5048.22
|
0.000
|
Square
|
4
|
1700.5
|
425.1
|
553.76
|
0.000
|
2-Way Interaction
|
6
|
190.8
|
31.8
|
41.42
|
0.000
|
Error
|
16
|
12.3
|
0.8
|
|
|
Lack-of-Fit
|
10
|
10.6
|
1.1
|
3.70
|
0.061
|
Pure Error
|
6
|
1.7
|
0.3
|
|
|
Total
|
30
|
17406.0
|
|
|
|
Source (BB)
|
|
|
|
|
|
Model
|
14
|
17901.5
|
1278.68
|
1869.79
|
0.000
|
Linear
|
4
|
14874.7
|
3718.68
|
5437.76
|
0.000
|
Square
|
4
|
2692.5
|
673.13
|
984.31
|
0.000
|
2-Way Interaction
|
6
|
334.3
|
55.71
|
81.46
|
0.000
|
Error
|
16
|
10.9
|
0.68
|
|
|
Lack-of-Fit
|
10
|
9.2
|
0.92
|
3.23
|
0.082
|
Pure Error
|
6
|
1.7
|
0.29
|
|
|
Total
|
30
|
17912.4
|
|
|
|
Table 5. The estimated effects and coefficients for the quadratic models of
%RTO and %RBB
Term
|
Effect
|
Coef
|
SE Coef
|
T-Value
|
P-Value
|
Constant %RTO
|
|
31.429
|
0.331
|
94.90
|
0.000
|
pH
|
42.292
|
21.146
|
0.179
|
118.23
|
0.000
|
m
|
25.058
|
12.529
|
0.179
|
70.05
|
0.000
|
TO
|
-11.858
|
-5.929
|
0.179
|
-33.15
|
0.000
|
BB
|
-5.158
|
-2.579
|
0.179
|
-14.42
|
0.000
|
pH*pH
|
5.446
|
2.723
|
0.164
|
16.62
|
0.000
|
M*m
|
1.696
|
0.848
|
0.164
|
5.18
|
0.000
|
TO*TO
|
14.696
|
7.348
|
0.164
|
44.85
|
0.000
|
BB*BB
|
4.446
|
2.223
|
0.164
|
13.57
|
0.000
|
pH*M
|
5.213
|
2.606
|
0.219
|
11.90
|
0.000
|
pH*TO
|
-4.212
|
-2.106
|
0.219
|
-9.62
|
0.000
|
m*TO
|
-1.312
|
-0.656
|
0.219
|
-3.00
|
0.009
|
M*BB
|
0.988
|
0.494
|
0.219
|
2.25
|
0.039
|
Constant %RBB
|
|
36.429
|
0.313
|
116.55
|
0.000
|
pH
|
40.442
|
20.221
|
0.169
|
119.79
|
0.000
|
m
|
27.375
|
13.688
|
0.169
|
81.09
|
0.000
|
TO
|
-7.108
|
-3.554
|
0.169
|
-21.06
|
0.000
|
BB
|
6.608
|
-3.304
|
0.169
|
19.57
|
0.000
|
pH*pH
|
5.042
|
2.521
|
0.155
|
16.30
|
0.000
|
m*m
|
5.042
|
2.521
|
0.155
|
16.30
|
0.000
|
TO*TO
|
9.517
|
4.758
|
0.155
|
30.77
|
0.000
|
BB*BB
|
-14.058
|
-7.029
|
0.155
|
-45.45
|
0.000
|
pH*m
|
7.962
|
3.981
|
0.207
|
19.26
|
0.000
|
pH*TO
|
-3.087
|
-1.544
|
0.207
|
-7.47
|
0.000
|
pH*BB
|
-1.988
|
-0.994
|
0.207
|
-4.81
|
0.000
|
m*BB
|
2.213
|
1.106
|
0.207
|
5.35
|
0.000
|
TO*BB
|
1.212
|
0.606
|
0.207
|
2.93
|
0.010
|
R-sqTO= 99.93% R-sq(adj)= 99.87% R-sq(pred)= 99.64%
R-sqBB= 99.94% R-sq(adj)= 99.89% R-sq(pred)= 99.69%
Table.6. Important isotherm parameters values for the adsorption of TO and BB on Fe3O4-PDA.
Langmuir
|
q max
|
b
|
R2
|
∆q
|
χ2
|
BB(sin)
TO(sin)
BB(bin)
TO(bin)
|
381
362
355
340
|
0.0047
0.0007
0.010
0.008
|
0.94
0.95
0.92
0.90
|
0.128
0.102
0.702
1.362
|
15.88
13.52
17.37
27.93
|
Freundlich
|
kf
|
n
|
R2
|
∆q
|
χ2
|
BB(sin)
TO(sin)
BB(bin)
TO(bin)
|
48
106
39
42
|
2,99
4.01
3.05
1.73
|
0.98
0.99
0.97
0.98
|
0.073
0.082
0.091
0.101
|
6.48
7.78
11.97
10.57
|
D-R
|
q max
|
B
|
R2
|
∆q
|
χ2
|
BB(sin)
TO(sin)
BB(bin)
TO(bin)
|
336
194
299
174
|
0.000010
0.000012
0.000627
0.000084
|
0.85
0.93
0.92
0.93
|
1.435
0.641
0.732
0.438
|
35.80
20.58
19.86
15.52
|
Temkin
|
kt
|
B
|
R2
|
∆q
|
χ2
|
BB(sin)
TO(sin)
BB(bin)
TO(bin)
|
82.9
49.7
15.2
13.2
|
0.82
0.90
118
69
|
0.94
0.96
0.93
0.93
|
0.195
0.097
0.607
0.953
|
17.25
9.02
16.41
17.78
|
sin= single system
bin= binary system
Table.7. Kinetics parameters for TO and BB adsorption onto Fe3O4-PDA in single and binary conditions.
SYSTEM
|
Pseudo first order
|
Pseudo second order
|
Intrapaeticle diffusion
|
|
aq(exp) b1q1 (cal) k1 R2
|
b2q2(cal) k2 the R2
|
kp cC R2
|
BB(sin)
|
145
|
3.03
|
0.303
|
0.889
|
166.6
|
0.36
|
0.999
|
0.68
|
143.6
|
0.988
|
TO(sin)
|
146
|
49.4
|
0.629
|
0.763
|
165.1
|
0.35
|
0.999
|
4.03
|
133.4
|
0.997
|
BB(bin)
|
137
|
240
|
0.731
|
0.674
|
142.8
|
0.012
|
0.997
|
11.28
|
92.91
|
0.956
|
TO(bin)
|
133
|
469
|
0.727
|
0.905
|
165.1
|
0.35
|
0.999
|
22.53
|
54.77
|
0.997
|
a: experimental uptake capacity; b1 and b2: calculated uptake capacity; c: intercept of intera-particle diffusion equation
Table.8.Thermodynamic results of the binary mixture absorption
TO and BB by nano-Fe3O4@PDA,
|
Temp(K)
|
*∆Gº(kJ/mol)
|
∆Hº(kJ/mol)
|
∆Sº(J/molK)
|
BB
|
293
303
313
323
|
-3.78
-4.35
-4.92
-4.49
|
13.0
|
57.2
|
TO
|
293
303
313
323
|
-5.90
-7.16
-8.42
-9.68
|
12.5
|
62.9
|
*Free energy is calculated at 25 ° C.