1
Supporting Information
2
Highly Efficient Adsorption of Rh(III) from Chloride Containing
3
Solutions by Triazine Polyamine Polymer
4
Merve Sayın a, Mustafa Can*b, Mustafa İmamoğlua and Mustafa Arslana
5
a
6
7
8
9
10
11
12
13
14
Department of Chemistry and b Vocational School of Arifiye, Sakarya University, Sakarya, Turkey.
* Corresponding Author: Mustafa Can, Sakarya University, Vocational School of Arifiye,
Fatih Mah. Eşit Sok. No:7/A 54580 – Arifiye/Sakarya - Turkey [email protected];
Tel.:
+90
(264)
295
33
52
fax:
+90
(264)
230
10
28
1
15
16
1. Adsorption Isotherms
To simulate the adsorption isotherm, here five commonly used models, the Langmuir,
17
Freundlich, Temkin, Dubinin–Radushkevich, and Redlich-Peterson, were selected to explicate
18
dye–pine sawdust interactions. These isotherms and its linear forms can be seen at Table 1.
19
The Langmuir equation initially derived from kinetic studies has been based on the
20
assumption that on the adsorbent surface there is a definite and energetically equivalent number
21
of adsorption sites. The bonding to the adsorption sites can be either chemical or physical, but it
22
must be sufficiently strong to prevent displacement of adsorbed molecules along the surface.
23
Thus, localised adsorption was assumed as being distinct from non-localised adsorption, where
24
the adsorbed molecules can move along the surface. Because the bulk phase is constituted by a
25
perfect gas, lateral interactions among the adsorbate molecules were neglected. On the
26
energetically homogeneous surface of the adsorbent a monolayer surface phase is thus formed.
27
Langmuir, for the first time, introduced a clear concept of the monomolecular adsorption on
28
energetically homogeneous surfaces 1,2.
29
Although there have been five different linear form of Langmiur isotherm equation named
30
as Langmuir 1, Competitive Langmuir 3, Lineweaver-Burk 4, Eadie-Hofstee 5,6,7, Scatchard 8,
31
and log-log 9, two most commonly used form, given in Table 1. Lineweaver-Burk linear form 4,
32
is very sensitive to errors, especially at the lower left corner of the chart, it is a very good
33
agreement with to the experimental data 9,10. The KL and aL are the Langmuir isotherm
34
constants and the KL/aL gives the theoretical monolayer saturation capacity, Q0.
35
36
2
37
Table 1. Adsorption isotherms and its lineer forms.
Isotherm
Langmuir linear 1,2
Linear Form
X&Y
𝐶𝑒
1 𝑎𝐿 𝐶𝑒
=
+
𝑞𝑒 𝐾𝐿
𝐾𝐿
𝑥 = 𝐶𝑒
𝑦 = 𝐶𝑒 ⁄𝑞𝑒
𝐾𝐿 𝐶𝑒
𝑞𝑒 =
1 + 𝑎𝐿 𝐶𝑒
Lineweaver-Burk
linear 4
𝑞𝑒 =
Freundlich 11
⁄
𝐾𝑓 𝐶𝑒1 𝑛
1
1 1 𝑎𝐿
=
+
𝑞𝑒 𝐾𝐿 𝐶𝑒 𝐾𝐿
𝑥 = 1⁄𝐶𝑒
1
log 𝑞𝑒 = − log 𝐾𝑓 + log 𝐶𝑒
𝑛
𝑥 = log 𝑐𝑒
𝑦 = 1⁄𝑞𝑒
𝑦 = log 𝑞𝑒
Slope & cut-off point
𝑎𝐿
tan 𝛼 =
𝐾𝐿
𝑐𝑢𝑡𝑜𝑓𝑓 =
1
𝐾𝐿
1
𝐾𝐿
𝑎𝐿
𝑐𝑢𝑡𝑜𝑓𝑓 =
𝐾𝐿
tan 𝛼 =
tan 𝛼 =
1
𝑛
𝑐𝑢𝑡𝑜𝑓𝑓 = −log 𝐾𝑓
38
39
The essential features of the Langmuir isotherm can be expressed in terms of a dimensionless
40
constant called separation factor (RL) which is defined by the following equation
1
41
𝑅𝐿 = 1+𝑎
42
where C0 (mg/L) is the initial dye concentration and aL (L/mg) is the Langmuir constant
43
related to the energy of adsorption. In this context, the value of RL indicates the shape of the
44
isotherms to be either unfavorable (RL > 1), linear (RL = 1), favorable (0 < RL <1) or irreversible
45
(RL = 0) 12,13. Langmuir linear form function graphic and their R2 values can be seen in Figure
46
S1(a).
𝐿 𝐶𝑜
(1)
3
2.6
0.07
y = 0.2032x + 0.0031
R² = 0.9989
0.06
y = 0.6552x + 0.9584
R² = 0.9375
2.4
2.2
0.05
y = 0.1433x + 0.0088
R² = 0.9889
0.03
log qe
1/qe
2
0.04
1.4
0.01
1.2
3M
3M
1
0
47
48
y = 0.3723x + 1.2167
R² = 0.8139
1.6
0.02
(a)
1.8
0
0.1
0.2
1/Ce
0.3
0.4
.200
(b)
.700
1.200 1.700
log Ce
2.200
Figure S1. Langmuir (a) and Freundlich (b) parameters and R2 values.
49
Freundlich isotherm is widely applied in heterogeneous systems especially for organic
50
compounds or highly interactive species on activated carbon and clays. The Freundlich isotherm
51
is an empirical equation employed to describe heterogeneous systems and equation shown in
52
Table 1. In this equation,𝐾𝑓 , (𝑚𝑔1−1⁄𝑛 𝐿1⁄𝑛 𝑔−1 ) is the Freundlich constant related to the bonding
53
energy, and 𝑛, (𝑔/𝐿) is the heterogeneity factor. The slope (1/n) ranges between 0 and 1 is a
54
measure of adsorption intensity or surface heterogeneity, and it becomes more heterogeneous
55
when its value gets closer to zero. Whereas, a value below unity implies chemisorptions process
56
where 1/n above one is an indicative of cooperative adsorption 12,14.
57
This model is the earliest known relationship describing the non-ideal reversible multilayer
58
adsorption with non-uniform distribution of adsorption heat and affinities over the heterogeneous
59
surface. In this perspective, the amount adsorbed is the summation of adsorption on all sites
60
(each having bond energy), with the stronger binding sites are occupied first, until adsorption
61
energy are exponentially decreased upon the completion of adsorption process 15. Its linearized
62
and non-linearized equations are listed in Table 1. Freundlich isotherm is criticized for its
4
63
limitation of lacking a fundamental thermodynamic basis, not approaching the Henry’s law at
64
vanishing concentrations 16.
65
By ignoring the extremely low and large value of concentrations, the derivation of the
66
Temkin isotherm assumes that the fall in the heat of sorption is linear rather than logarithmic.
67
Temkin equation is excellent for predicting the gas phase equilibrium, conversely complex
68
adsorption systems including the liquid-phase adsorption isotherms are usually not appropriate to
69
be represented 17. In this equation, A (L/mg) is the equilibrium binding constant corresponding
70
to the maximum binding energy, b (J/mol) is Temkin isotherm constant and constant B
71
(dimensionless) is related to the heat of adsorption. Langmuir linear form function graphic and
72
their R2 values can be seen in Figure S1(b).
73
2. Adsorption kinetics
74
In the industrial usage of adsorbents, the time dependence of adsorption on solid surfaces is
75
named as adsorption kinetics. To examine the mechanism of adsorption process such as mass
76
transfer and chemical reaction, a suitable kinetic model is needed to analyze the rate data. Many
77
models such as homogeneous surface diffusion model, pore diffusion model, and heterogeneous
78
diffusion model (also known as pore and diffusion model) have been extensively applied in batch
79
reactors to describe the transport of adsorbates inside the adsorbent particles 18; however, the
80
mathematical complexity of these models makes them rather inconvenient for practical use. The
81
large number and array of different functional groups on the activated carbon surfaces (e.g.
82
carboxylic, carbonyl, hydroxyl, ether, quinone, lactone, anhydride, etc) indicate that there are
83
many types of adsorbent-solute interactions. Any kinetic or mass transfer representation is likely
5
84
to be global. From a system design viewpoint, a lumped analysis of kinetic data is hence
85
sufficient for practical operation.
86
Table 2. Used adsorption kinetic equation.
Equation
Lagergren
first 19
pseudo
Pseudo second-order
20
𝑑𝑞𝑡
𝑑𝑡
𝑑𝑞𝑡
𝑑𝑡
Integrated Linear From
= 𝑘 1 (𝑞 𝑒 − 𝑞 𝑡 )
= 𝑘 2 (𝑞 𝑒 − 𝑞 𝑡 )
2
log(𝑞𝑒 − 𝑞𝑡 ) = log 𝑞𝑒 −
𝑡
𝑞𝑡
=
1
𝑘𝑞2𝑒
+
1
𝑞𝑒
𝑡
𝑘1
𝑡
2,303
Constants
𝑘1 (min.-1)
𝑘2 (𝑔. 𝑚𝑔−1 . 𝑚𝑖𝑛.−1 )
87
88
To simulate the adsorption kinetics, here five commonly used models, pseudo first- and
89
second-order equation, intraparticle diffusion equation and the Elovich equation, were applied
90
for dye– red pine sawdust interactions. These isotherms can be seen at Table 2.
91
In 1898, Lagergren expressed the pseudo first-order rate equation for liquid-solid
92
adsorption systems based on solid capacity 19. Later on this equation has been called pseudo-
93
first order equation. In recent years, a second-order kinetic equation has been described sorption,
94
which included chemisorption and provided a different idea to the second-order equation called a
95
pseudo-second-order rate expression 20. The process can be described by a pseudo-second order
96
model based on the assumption that the rate limiting step may be chemical sorption or
97
chemisorption between sorbent and sorbate. The parameter which has the influence on the
98
kinetics of the sorption reaction was the sorption equilibrium capacity, qe, which is a function of
99
initial dye concentrations, red pine sawdust dose and the nature of dyes. The pseudo-second-
100
order equation has the following advantages: it does not have the problem of assigning an
101
effective sorption capacity; the sorption capacity, rate constant of pseudo-second-order, and the
6
102
initial sorption rate can all be determined from the equation without knowing any parameter
103
beforehand 21.
104
In the industrial usage of adsorbents, the time dependence of adsorption on solid surfaces is
105
named as adsorption kinetics. With the development of the theory of equilibria of adsorption on
106
heterogeneous solid surfaces, the theory of adsorption-desorption kinetics on heterogeneous
107
surfaces was also developed. Adsorption kinetics is determined by the following stages:
108
109
1. Diffusion of molecules from the bulk phase towards the interface space (so-called
external diffusion)
110
2. Diffusion of molecules inside the pores (internal diffusion)
111
3. Diffusion of molecules in the surface phase (surface diffusion)
112
4. Adsorption-desorption elementary processes.
113
In the case of sorption kinetics on microporous solids, a series of other mechanisms may
114
additionally take place, sui generis. Diffusion in micropores carries the character of activated
115
diffusion which usually, is described by Weber and Morris 22. Before sorbing species may enter
116
micropores, the penetration of surface barriers may be necessary. When adsorption systems fit
117
Langmuir isotherm equation, that means adsorbent has non-porous and macroporous character.
118
For non-porous and macroporous solids the internal diffusion may be neglected. In this case, the
119
adsorption kinetics is determined by external diffusion and molecular adsorption-desorption
120
processes. The Langmuirian kinetics, based on the ideal monolayer adsorbed model, proved to be
121
deceptive for most real adsorption systems that include structurally high porous and energetically
122
heterogeneous solids. On the other hand, the adsorption-desorption kinetics theories are
7
123
technologically extremely important, because the diffusion of adsorbed particles on solid
124
surfaces is a phenomenon of great importance in catalysis, metallurgy, microelectronics, material
125
science and other numerous scientific and technological applications 15.
126
127
Integrated linear pseudo-first and pseudo-second order kinetic equation form function
graphics and their R2 values can be seen in Figure S2.
3
60
3M
0.1M
2.5
50
2
y = -0.0018x + 2.2818
R² = 0.991
ln (qe-qt)
1.5
1
30
t/qt
0
-0.5
-1
y = 0.0276x + 1.5503
R² = 0.9989
20
10
y = -0.002x + 2.0502
R² = 0.9229
-1.5
0
-2
0
130
y = 0.0278x + 1.0655
R² = 0.9999
40
0.5
128
129
3M
0.1M
500
1000
1500
t (minute)
2000
0
500
1000
1500
t (minute)
2000
Figure S2. Pseudo-first (a) and pseudo-second (b) order kinetic equation parameters and R2 values.
4. FTIR Spectras
8
Transmittance
TAPEHA Recycle 3M
TAPEHA Recycled 0.1M
TAPEHA-Rh 3M
TAPEHA-Rh 0.1M
TAPEHA
3600
131
132
133
134
135
136
3100
2600
2100
Wavenumbers (1/cm)
1600
1100
600
Figure S3. FTIR spectras of TAPEHA polymer before, after and regenerated states in 3 and 0.1 M HCl
concantrations.
References
1. Langmuir, I. The Adsorption Of Gases On Plane Surface Of Glass, Mica And Platinum. Journal of the
American Chemical Society, 1918, 1361–1403.
2. Langmuir, I. The constitution and fundamental properties of solids and liquids. Journal Of The
American Chemical Society, 1916, 2221–2295.
3. Altın, O.; Özbelge, H. Ö.; Doğu, T. Use of General Purpose Adsorption Isotherms for Heavy Metal–
Clay Mineral Interactions. Journal of Colloid and Interface Science, 1998, 130-140.
4. Lineweaver, H.; Burk, D. The Determination of Enzyme Dissociation Constants. Journal of the
American Chemical Society, 1934, 658–666.
5. Eadie, G. S. The inhibition of cholinesterase by physostigmine and prostigmine. Journal Of Biological
Chemistry, 1942, 85-93.
9
6. Eadie, G. S. On the Evaluation of the Constants Vm and KM in Enzyme Reactions. Science, 1952, 688.
7. Hofstee, B. H. J. Non-Inverted Versus Inverted Plots in Enzyme Kinetics. Nature 1959, 184, 1296 1298.
8. Scatchard, G. The attractions of proteins for small molecules and ions. Annals Of The New York
Academy Of Science, 1949, 660-672.
9. El-Khaiary, M. I. Least-squares regression of adsorption equilibrium data: Comparing the options.
Journal of Hazardous Materials, 2008, 73–87.
10. Bolster, C. H.; Hornberger, G. M. On the Use of Linearized Langmuir Equations. Soil Science Society of
America Journal, 2007, 1796-1806.
11. Freundlich, H. M. F. Über die adsorption in lösungen. Z. Phys. Chem., 1906, 385–471.
12. Foo, K. Y.; Hameed, B. H. Insights into the modeling of adsorption isotherm systems. Chemical
Engineering Journal, 2010, 2-10.
13. Webber, T. W.; Chakkravorti, R. K. Pore and solid diffusion models for fixed-bed adsorbers. AlChE
Journal, 1974, 228–238.
14. Crini, G.; Peindy, H. N.; Gimbert, F.; Robert, C. Removal of C.I. Basic Green 4 (Malachite Green) from
aqueous solutions by adsorption using cyclodextrin-based adsorbent: Kinetic and equilibrium
studies. Separation and Purification Technology, 2007, 97-110.
15. Dabrowski, A. Adsorption - from theory to practice. Advances in Colloid and Interface Science, 93
2001, 135-224.
16. Ho, Y. S.; Porter, J. F.; McKay, G. Equilibrium isotherm studies for the sorption of divalent metal ions
onto peat: Copper, nickel and lead single component systems. Water, Air, and Soil Pollution 2002,
141 (1-4), 1-33.
17. Kim, Y.; Kim, C.; Choi, I.; Rengraj, S.; Yi, J. Arsenic Removal Using Mesoporous Alumina Prepared via a
Templating Method. Environmental Science & Technology 2004, 38 (3), 924-931.
18. Wu, F.-C.; Tseng, R.-L.; Juang, R.-S. Adsorption of Dyes and Phenols from Water on the Activated
Carbons Prepared from Corncob Wastes. Environmental Technology 2001, 22 (2), 205-213.
19. Lagergren, S. Zur theorie der sogenannten adsorption gelöster stoffe. Kungliga Svenska
Vetenskapsakademiens. Handlingar, 1898.
20. Ho, Y. S.; McKay, G. Pseudo-second order model for sorption processes. Process Biochemistry, 1999,
10
451-465.
21. Ho, Y. S. Second-order kinetic model for the sorption of cadmium onto tree fern: a comparison of
linear and non-linear methods. Water Research 2006, 40 (1), 119–125.
22. Weber Jr., W. J.; Morris, J. C. Intraparticle diffusion during the sorption of surfactants onto activated
carbon. Journal of Saint, Engineering Division of American Society of Civil Engineers, 1963.
23. Radushkevich, L. V. Potential theory of sorption and structure of carbons. Zhurnal Fizicheskoi Khimii
1949, 23, 1410–1420.
24. Dubinin, M. M. Modern state of the theory of volume filling of micropore adsorbents during
adsorption of gases and steams on carbon adsorbents. Zhurnal Fizicheskoi Khimii 1965, 39, 1305–
1317.
25. Özcan, A. S.; Erdem, B.; Özcan, A. Adsorption of Acid Blue 193 from aqueous solutions onto BTMAbentonite. Colloids and Surfaces A: Physicochemical and Engineering Aspects 2005, 266 (1-3), 73-81.
26. Redlich, O.; Peterson, D. L. A Udeful Adsorpsiton Isotherm. The Journal of Physical Chemistry A,
1959, 1024.
27. Kumar, K. V.; Sivanesan, S. Comparison of linear and non-linear method in estimating the sorption
isotherm parameters for safranin onto activated carbon. Journal of Hazardous Materials, 2005, 288292.
28. Ho, Y. S. Selection of optimum sorption isotherm. Carbon, 2004, 2113–2130.
29. Taylor, A.; Thon, N. Kinetics of Chemisorption. Journal of the American Chemical Society, 1952.
30. Zeldovich, Y. Ada physicochim. (U.R.S.S.), 1934.
31. Roginskii, S.; Zeldovich, Y. ibid., (U.R.S.S.). 1934.
32. Elovich, S. Y..; Zhabrova, G. R. Zhur. Fiz. Khim. (U.R.S.S.), 1939.
33. Temkin, M. I. Adsorption Equilibrium and Kinetics of Processes on Heterogeneous Surfaces and at
Interaction between Adsorbed Molecules. Zh. Fiz. Khim.(Russian Journal Of Physical Chemistry),
1941, 296.
138
11