Chapter 7: Experimental Validation
7.3 Fluid Flow Results
7.3.2 Pathlines
Traditionally, the sorption of ions by adsorbents has been quantitatively described by parameters obtained either directly from isotherms or by least square analysis with sorption isotherms. The data from this study was subjected to Freundlich, Langmuir, Temkin and Dubinin Radushkovich isotherm models to determine sorption parameters and identify the model which best fit or describes the adsorption by these prepared activated carbons.
The Freundlich model is a case for heterogeneous surface energies and it gives an exponential distribution of active sites present in the activated carbon (AC). This form of the equation was used to relate the amount of heavy metal ions sorbed from the metal solutions and the linear form of the model is
logqe = logKf + 1/nlogCe (4.1) where qe is the amount of sorbed metal ions in mg/g, Ce is the equilibrium concentration of the metal ions. n and Kf are the Freundlich constants which respectively indicates the adsorption intensity and the adsorption capacity of the AC (Uddin et al., 2007; Khan, et al., 2005). They are calculated from the slope and intercept of the plot of logqe versus log Ce.
132
Figues 4.4 to 4.11 presents the adsorption of Ni on OBAC carbonized at both 600oC and 800oC for 30min and activated with HCl, H2SO4 and H3PO4. The parameters for the plot of the freundlich, Langmuir, Temkin and Dubinin-Radushkevich isotherm models are also presented in appendix C.
Figure 4.4: Freundlich isotherm plot for Ni onto OBAC Carbonized at 600oC and activated with HCl, H3PO4, H2SO4
Figure 4.4 showed the result of the adsorption isotherm for Ni on OBAC carbonised at 600oC and activated with HCl, H2SO4 and H3PO4 at the same temperature. From the figure, the straight line plot indicated the occurrence of Ni metal adsorption from the sample. The graph showed the adsorption isotherm is of relative good fit on Freundlich model. This is indicated by the coefficient of determination (R2) ranging from 0.603 to 0.901. The goodness of fit of an experimental data is measured by the determination coefficient (R2) (Zaid and Mohammed, 2008). The R2 for all the isotherms are presented in Table 4.122. The slope of the linear plot is also good and suitable for testing the adsorption effectiveness. The value of n obtained from the slope of the linear plot ranged from 1.91 to 15.9 which indicated the strength of the OBAC as an adsorbent. When n > 1, the adsorption coefficient
-0.8 -0.6 -0.4 -0.2 0
0 0.5 1 1.5 2
Logqe
LogCe y = -0.077x - 0.247
R² = 0.693
y = -0.164x - 0.205 R² = 0.603
y = -0.524x + 0.203 R² = 0.901
133
increases with increasing concentration of the solution which lead to an increase in hydrophobic surface characteristic after monolapisan and when n < 1, Kf decreases with concentration (Hamidi-Aziz et al., 2003). Appendix G showed the Atomic Absorption Spectrophotometer (AAS) results of the heavy metal analysis.
Figure 4.5: Freundlich isotherm plot for Ni onto OBAC Carbonized at 800oC and activated with HCl, H3PO4, H2SO4
Figure 4.6: Langmuir isotherm plot for Ni onto OBAC Carbonized at 600oC and activated with HCl, H3PO4, H2SO4
The Langmuir isotherm model suggested that sorption occured on homogeneous surface by monolayer sorption without interaction between sorbed ions. The linear form of Langmuir isotherm equation is as presented below:
1/qe = 1/Qo + 1/bQo1/Ce (4.2) Where Ce is the equilibrium concentration (mg/l), qe is the amount of metal ions adsorbed at equilibrium (mg/g) and the Qo and b are the Langmuir isotherm constants which gives the adsorption capacity and the energy of adsorption
-2 -1.5 -1 -0.5 0
0 0.5 1 1.5 2
Logqe
LogCe
0 2 4 6
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
1/qe
1/Ce
y = -0.524x + 0.203 R² = 0.901
y = -0.074x - 0.465 R² = 0.001
y = -0.881x + 0.402 R² = 0.739
y = -30.75x + 5.216 R² = 0.861
y = -0.707x + 2.224 R² = 0.477
y = -1.181x + 2.562 R² = 0.249
134
respectively (Uddin, 2007). The linear plot of 1/qe versus 1/Ce indicated the Langmuir model plot and the values of Qo and b were calculated from the slopes and intercepts of the Langmuir plots respectively.
Figure 4.7: Langmuir isotherm plot for Ni onto OBAC Carbonized at 800oC and activated with HCl, H3PO4, H2SO4
In Figures 4.6 and 4.7, the determination coefficient did not show a good fit and the Langmuir adsorption capacity (Qo) of the three type of OBAC for Ni ranged from 0.035 to 1.4144l/kg, while the Langmuir energy of adsorption (b) ranged from 0.32 to 5.895 which reflect the retention intensity and the number of sites available for a sorbate.
For the adsorption of Ni by OBAC carbonised at 800oC, the Kf ranged from 2.5 to 2.9 which was an indication of good adsorptive capacity. Also, the adsorption intensity ranged from 0.001 to 0.739. The determination coefficient of the Freundlich plot indicated poor fit except for that activated with HCl.
The adsorption data for OBAC carbonised at 600oC had a better fit for the Freundlich model and so indicated heterogeneous nature of the activated carbon surface energies. The Freundlich intensity of adsorption (n) of Ni on OBAC was
0 10 20 30 40
0 0.05 0.1 0.15 0.2
1/qe
1/Ce
y = -287.9x + 16.26 R² = 0.82
y = 3.005x + 3.746 R² = 0.000
y = -83.78x + 14.88 R² = 0.213
135
relatively high, but the reverse was the case for the Freundlich adsorption capacity of the (Kf) values for OBAC.
Figure 4.8: Temkin isotherm plot for Ni onto OBAC Carbonized at 600oC and activated with HCl, H3PO4, H2SO4
The data obtained from the Ni adsorption onto OBAC fitted well on the Temkin model as indicated by the determination coefficients except for that carbonized at 800oC and activated with H2SO4, R2 = 0.010 (Figure 4.9).
Figure 4.9: Temkin isotherm plot for Ni onto OBAC Carbonized at 800oC and activated with HCl, H3PO4, H2SO4
The determination coefficients for the adsorption of Ni onto OBAC showed the data fitted poorly on the D-R isotherm model except for that activated with H3PO4
(Figure 4.10 and 4.11).
0 0.2 0.4 0.6 0.8
0 1 2 3 4 5
qe(mg/g)
InCe
0 0.2 0.4 0.6
0 1 2 3 4 5
qe(mg/g)
InCe
y = -0.065x + 0.597 R² = 0.563
y = -0.170x + 0.870 R² = 0.844
y = -0.036x + 0.560 R² = 0.706
y = -0.056x + 0.466 R² = 0.01
y = -0.171x + 0.805 R² = 0.921
y = -0.113x + 0.544 R² = 0.960
136
Figure 4.10: Dubinin Rudushkevich isotherm plot for Ni onto OBAC Carbonized at 600oC and activated with HCl, H3PO4, H2SO4
Figure 4.11: Dubinin Rudushkevich isotherm plot for Ni onto OBAC Carbonized at 800oC and activated with HCl, H3PO4, H2SO4
Figure 4.12: Freundlich isotherm plot for Cd onto OBAC Carbonized at 600oC and activated with HCl, H3PO4, H2SO4
The data obtained from the adsorption of Cd onto OBAC fitted well on the Freundlich model as indicated by the determination coefficients except for that carbonized at 800oC and activated with H2SO4, R2 = 0.022 (Figures 4.12 and 4.13).
This is an indication of heterogeneous adsorption as suggested by Freundlich model.
-2 -1.5 -1 -0.5 0
0 0.5 1 1.5 2
Inqe
Ԑ2/1M
-4 -3 -2 -1 0
0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16
Inqe
Ԑ2/1M
-1.5 -1 -0.5 0
-0.5 0 0.5 1 1.5 2
Logqe
LogCe
y = 0.132x - 0.769 R² = 0.416 y = 0.126x - 0.824 R² = 0.136 y = 12.00x - 1.446 R² = 0.702
y = 10.83x - 1.392 R² = 0.003 y = 9.292x - 1.898 R² = 0.297 y = 6.992x - 1.958 R² = 0.458
y = -0.075x - 0.282 R² = 0.841
y = -1.723x + 1.729 R² = 0.917
y = -1.586x + 1.634 R² = 0.999
137
Figure 4.13: Freundlich isotherm plot for Cd onto OBAC Carbonized at 800oC and activated with HCl, H3PO4, H2SO4
Figure 4.14: Langmuir isotherm plot for Cd onto OBAC Carbonized at 600oC and activated with HCl, H3PO4, H2SO4
The data obtained for the adsorption of Cd onto OBAC fitted poorly on the Langmuir isotherm model as indicated by R2 and this is an indication that its adsorption does not follow monolayer coverage as suggested by Langmuir model.
Figure 4.15: Langmuir isotherm plot for Cd onto OBAC Carbonized at 800oC and activated with HCl, H3PO4, H2SO4
-2 -1.5 -1 -0.5 0
0 0.5 1 1.5 2
Logqe
LogCe
-10 0 10 20 30
0 0.5 1 1.5 2 2.5
1/qe
1/Ce
-10 0 10 20 30 40 50 60
0 0.02 0.04 0.06 0.08 0.1
1/qe
1/Ce
y = -1.325x + 1.114 R² = 0.815
y = -0.570x + 0.045 R² = 0.022
y = -4.274x + 5.882 R² = 0.934
y = -0.205x + 2.208 R² = 0.440
y = -314.7x + 17.19 R² = 0.993
y = -392.0x + 24.60 R² = 0.657
y = -665.5x + 24.34 R² = 0.140
y = -3067.x + 91.90 R² = 0.717
y = -219.6x + 19.34 R² = 0.490
138
Figure 4.16: Temkin Isotherm plot for Cd onto OBAC Carbonized at 600oC and activated with HCl, H3PO4, H2SO4
Figures 4.16 and 4.17 presents the Temkin isotherm plot for Cd adsorption onto OBAC at both activation temperatures. The R2 showed that the data fitted well with the model in most of them having ranged from 0.835 to 0.998 for those carbonized at 600oC and 0.019 to 0.998 for those carbonized at 800oC respectively.
Figure 4.17: Temkin Isotherm plot for Cd onto OBAC Carbonized at 800oC and activated with HCl, H3PO4, H2SO4
Figure 4.18: Dubinin Rudushkevich Isotherm plot for Cd onto OBAC Carbonized at 600oC and activated with HCl, H3PO4, H2SO4
Presented in Figures 4.18 and 4.19 are the D-R plot for the adsorption of Cd onto OBAC at 600oC and 800oC respectively. The fitness of the data on the model is
0 0.2 0.4 0.6
-1 0 1 2 3 4 5
qe(mg/g)
InCe
0 0.2 0.4 0.6
0 1 2 3 4 5
qe(mg/g)
InCe
-4 -3 -2 -1 0
0 1 2 3 4 5 6 7 8
Inqe
Ԑ2/1M
y = -0.035x + 0.522 R² = 0.835
y = -0.287x + 1.201 R² = 0.998
y = -0.279x + 1.163 R² = 0.986
y = 0.069x - 0.117 R² = 0.019
y = -0.355x + 1.448 R² = 0.998
y = -0.237x + 1.019 R² = 0.968
y = 131.7x - 2.706 R² = 0.994 y = 90.08x - 2.764 R² = 0.729 y = 0.021x - 0.757 R² = 0.334
139
relatively good for both temperatures of activation considering the determination coefficients but those of Temkin were better.
Figure 4.19: Dubinin Rudushkevich Isotherm plot for Cd onto OBAC Carbonized at 800oC and activated with HCl, H3PO4, H2SO4
Figure 4.20: Freundlich isotherm plot for Pb onto OBAC Carbonized at 600oC and activated with HCl, H3PO4, H2SO4
Figures 4.20 and 4.21 showed the freundlich adsorption isotherms for Pb adsorption onto OBAC at both 600oC and 800oC respectively. They all had good determination coefficients except for those activated with H3PO4 at both carbonization temperatures.
-5 -4 -3 -2 -1 0
0 0.01 0.02 0.03 0.04 0.05
Inqe
Ԑ2/1M
-1.5 -1 -0.5 0
1.4 1.45 1.5 1.55 1.6 1.65 1.7 1.75
Logqe
LogCe
-0.6 -0.4 -0.2 0
-2.5 -2 -1.5 -1 -0.5 0 0.5 1
Logqe
LogCe
y = 608.1x - 4.665 R² = 0.848 y = 120.5x - 2.443 R² = 0.035 y = 38.39x - 2.332 R² = 0.561
y = 1.745x - 3.681 R² = 0.727 y = 1.065x - 2.812 R² = 0.763 y = 1.243x - 3.190 R² = 0.388
y = 0.224x - 0.333 R² = 0.939 y = 0.216x - 0.383 R² = 0.985 y = 0.034x - 0.319 R² = 0.089
140
Figure 4.21: Freundlich isotherm plot for Pb onto OBAC Carbonized at 800oC and activated with HCl, H3PO4, H2SO4
Figure 4.22: Langmuir isotherm plot for Pb onto OBAC Carbonized at 600oC and activated with HCl, H3PO4, H2SO4
Figure 4.23: Langmuir isotherm plot for Pb onto OBAC Carbonized at 800oC and activated with HCl, H3PO4, H2SO4
Figure 4.24: Temkin Isotherm plot for Pb onto OBAC Carbonized at 600oC and activated with HCl, H3PO4, H2SO4
Figures 4.24 and 4.25 presents the Temkin adsorption isotherms for Pb adsorption onto OBAC at both 600oC and 800oC respectively. They all had good determination coefficients except for those activated with H2SO4 at both carbonization temperatures.
0 10 20 30
0 0.01 0.02 0.03 0.04
1/qe
1/Ce
0 1 2 3 4
0 20 40 60 80 100 120
1/qe
1/Ce
0 0.05 0.1 0.15 0.2
3.3 3.4 3.5 3.6 3.7 3.8 3.9 4
qe(mg/g
InCe
y = 617.8x - 9.650 R² = 0.385 y = 628.9x + 1.102 R² = 0.250 y = 565.4x - 1.306 R² = 0.706
y = 0.374x + 1.677 R² = 0.885 y = 0.000x + 2.241 R² = 0.004 y = 0.536x + 1.756 R² = 0.950
y = 0.189x - 0.563 R² = 0.624 y = 0.079x - 0.212 R² = 0.803 y = 0.087x - 0.254 R² = 0.463
141
Figure 4.25: Temkin Isotherm plot for Pb onto OBAC Carbonized at 800oC and activated with HCl, H3PO4, H2SO4
Figure 4.26: Dubinin Rudushkevich Isotherm plot for Pb onto OBAC Carbonized at 600oC and activated with HCl, H3PO4, H2SO4
The adsorption data obtained for Pb on D-R model showed good fit for both carbonization temperatures except for those activated with H2SO4 (Figures 4.26 and 4.27).
Figure 4.27: Dubinin Rudushkevich Isotherm plot for Pb onto OBAC Carbonized at 800oC and activated with HCl, H3PO4, H2SO4
0 0.2 0.4 0.6
-5 -4 -3 -2 -1 0 1 2
qe(mg/g)
InCe
-3.5 -3 -2.5 -2 -1.5 -1 -0.5 0
0 0.002 0.004 0.006 0.008
Inqe
Ԑ2/1M
-1.5 -1 -0.5 0
0 20 40 60 80 100 120 140
Inqe
Ԑ2/1M
y = 0.095x + 0.419 R² = 0.977 y = 0.101x + 0.472 R² = 0.955 y = 0.018x + 0.492 R² = 0.121
y = -126.9x - 2.031 R² = 0.745
y = -182.7x - 1.334 R² = 0.739
y = -121.5x - 2.277 R² = 0.267
y = -0.038x - 0.582 R² = 0.896
y = -0.000x - 0.764 R² = 0.038
y = -0.055x - 0.635 R² = 0.906
142
Figure 4.28: Freundlich Isotherm plot for Mn onto OBAC Carbonized at 600oC and activated with HCl, H3PO4, H2SO4
Figures 4.28 and 4.29 presents the isotherm plot, equation of the plot, as well as the determination coefficients for the fit of Freundlich model by the data obtained. It showed that all the activated carbon fitted poorly on the adsorption of Mn except for the carbonization at 800oC and HCl activation.
Figure 4.29: Freundlich Isotherm plot for Mn onto OBAC Carbonized at 800oC and activated with HCl, H3PO4, H2SO4
Figure 4.30: Langmuir Isotherm plot for Mn onto OBAC Carbonized at 600oC and activated with HCl, H3PO4, H2SO4
-1.5 -1 -0.5 0
1.8 1.9 2 2.1 2.2
Logqe
LogCe
-0.8 -0.6 -0.4 -0.2 0 0.2
0 0.5 1 1.5 2 2.5
Logqe
LogCe
y = 2.394x - 5.693 R² = 0.422 y = 0.624x - 2.281 R² = 0.132
y = -0.031x - 1.195 R² = 0.001
y = -0.349x + 0.307 R² = 0.826
y = -0.487x + 0.524 R² = 0.479
y = -0.220x - 0.012 R² = 0.366
0 10 20 30
0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016
1/qe
1/Ce
y = 467.2x + 6.811 R² = 0.066 y = 1748.x - 7.473 R² = 0.319
y = -121.8x + 19.63 R² = 0.008
143
Mn adsorption on to OBAC also did not follow Langmuir model as shown by the having had poor determination coefficients in all except for the carbonization at 800oC which showed improved fitness with HCl activation (Figures 4.30 and 4.31).
Figure 4.31: Langmuir Isotherm plot for Mn onto OBAC Carbonized at 800oC and activated with HCl, H3PO4, H2SO4
Figure 4.32: Temkin Isotherm plot for Mn onto OBAC Carbonized at 600oC and activated with HCl, H3PO4, H2SO4
From figure 4.32 and 4.33 the data for adsorption of the metals fitted well on the Temkin model except for those carbonized at 800oC and activated with H2SO4 for Ni, Cd and Pb but for Mn.
Figure 4.33: Temkin Isotherm plot for Mn onto OBAC Carbonized at 800oC and activated with HCl, H3PO4, H2SO4
0 2 4 6
0 0.2 0.4 0.6 0.8 1
1/qe
1/Ce
-0.1 0 0.1 0.2 0.3 0.4
4 4.2 4.4 4.6 4.8 5
qe(mg/g)
InCe
0 0.5 1 1.5
0 1 2 3 4 5 6
qe(mg/g)
InCe
y = -12.26x + 2.594 R² = 0.892
y = -54.86x + 3.502 R² = 0.355
y = -1.940x + 3.125 R² = 0.168
y = 0.329x - 1.356 R² = 0.458 y = 0.207x - 0.882 R² = 0.722
y = -0.001x + 0.062 R² = 0.001
y = -0.238x + 1.508 R² = 0.720
y = -0.091x + 0.858 R² = 0.345
y = -0.197x + 1.298 R² = 0.401
144
Figure 4.34: Dubinin Rudushkevich Isotherm plot for Mn onto OBAC Carbonized at 600oC and activated with HCl, H3PO4, H2SO4
For the Dubinin Rudushkevich Isotherm model, the data generally speaking, did not fit well for all the metals studied.
Figure 4.35: Dubinin Rudushkevich Isotherm plot for Mn onto OBAC Carbonized at 800oC and activated with HCl, H3PO4, H2SO4
Figure 4.36: Freundlich Isotherm plot for Ni onto PNAC Carbonized at 600oC and activated with HCl, H3PO4, H2SO4
The adsorption of Ni on PNAC for both carbonization temperatures showed high values for the determination coefficients indicating good fit of the data obtained on the four isotherm models tested (Figures 4.36, 4.43).
-4 -3 -2 -1 0
0 0.0002 0.0004 0.0006 0.0008 0.001 0.0012 0.0014
Inqe
Ԑ2/1M
-2 -1.5 -1 -0.5 0 0.5
0 0.5 1 1.5 2 2.5 3
Inqe
Ԑ2/1M
-1.5 -1 -0.5 0
0 0.5 1 1.5 2
Logqe
LogCe
y = -365.5x - 2.107 R² = 0.090
y = 66.11x - 2.937 R² = 0.016
y = -1351.x - 1.151 R² = 0.377
y = 9.330x - 0.856 R² = 0.767 y = 0.228x - 0.917 R² = 0.145 y = 54.82x - 0.979 R² = 0.159
y = -1.641x + 1.792 R² = 0.861
y = -0.678x + 0.446 R² = 0.924
y = -0.180x - 0.259 R² = 0.596
145
Figure 4.37: Freundlich Isotherm plot for Ni onto PNAC Carbonized at 800oC and activated with HCl, H3PO4, H2SO4
Figure 4.38: Langmuir Isotherm plot for Ni onto PNAC Carbonized at 600oC and activated with HCl, H3PO4, H2SO4
Figure 4.39: Langmuir Isotherm plot for Ni onto PNAC Carbonized at 800oC and activated with HCl, H3PO4, H2SO4
Figure 4.40: Temkin Isotherm plot for Ni onto PNAC Carbonized at 600oC and activated with HCl, H3PO4, H2SO4
Ni adsorption data onto PNAC fitted well by the Temkin model for both carbonization temperatures as indicated by the determination coefficients recorded from the isotherm plot (Figure 4.40 and 4.41).
-1.5 -1 -0.5 0
0 0.5 1 1.5 2
Logqe
LogCe
-50 0 50 100 150
0 0.01 0.02 0.03 0.04 0.05 0.06
1/qe
1/Ce
0 5 10 15
0 0.01 0.02 0.03 0.04 0.05 0.06
1/qe
1/Ce
0 0.2 0.4
0 1 2 3 4 5
qe(mg/g)
InCe
y = -0.672x + 0.423 R² = 0.792
y = -0.699x + 0.462 R² = 0.888
y = -1.402x + 1.447 R² = 0.883
y = -468.8x + 21.63 R² = 0.630
y = -17.42x + 3.977 R² = 0.629
y = -2219.x + 102.7 R² = 0.603
y = -85.02x + 6.733 R² = 0.728
y = -89.63x + 6.943 R² = 0.838
y = -256.4x + 14.44 R² = 0.727
y = -0.25x + 1.102 R² = 0.947
y = -0.055x + 0.486 R² = 0.646
y = -0.268x + 1.176 R² = 0.884
146
Figure 4.41: Temkin Isotherm plot for Ni onto PNAC Carbonized at 800oC and activated with HCl, H3PO4, H2SO4
Figure 4.42: Dubinin Rudushkevich Isotherm plot for Ni onto PNAC Carbonized at 600oC and activated with HCl, H3PO4, H2SO4
Figure 4.43: Dubinin Rudushkevich Isotherm plot for Ni onto PNAC Carbonized at 800oC and activated with HCl, H3PO4, H2SO4
Figure 4.44: Freundlich Isotherm plot for Pb onto PNAC Carbonized at 600oC & activated with HCl, H3PO4, H2SO4
The adsorption of Pb on PNAC for both carbonization temperatures also showed high values for the determination coefficients indicating good fit of the data obtained on the four isotherm models tested (Figures 4.44 to 4.51).
0 0.2 0.4 0.6
0 1 2 3 4 5
qe(mg/g)
InCe
-5 -4 -3 -2 -1 0
0 0.005 0.01 0.015 0.02
Inqe
Ԑ2/1M
-3 -2 -1 0
0 0.005 0.01 0.015 0.02
Inqe
Ԑ2/1M
-0.6 -0.4 -0.2 0
-0.4 -0.2 0 0.2 0.4 0.6 0.8
Logqe
LogCe
y = -0.175x + 0.870 R² = 0.883
y = -0.170x + 0.854 R² = 0.807
y = -0.285x + 1.248 R² = 0.841
y = 195.8x - 3.547 R² = 0.549 y = 12.22x - 1.306 R² = 0.628 y = 151.3x - 2.670 R² = 0.691
y = 53.15x - 1.713 R² = 0.748 y = 55.55x - 1.744 R² = 0.803 y = 103.5x - 2.319 R² = 0.739
y = 0.172x - 0.384 R² = 0.650 y = 0.190x - 0.398 R² = 0.820
y = -0.037x - 0.355 R² = 0.021
147
Figure 4.45: Freundlich Isotherm Plot for Pb onto PNAC Carbonized at 800oC and activated with HCl, H3PO4, H2SO4
Figure 4.46: Langmuir Isotherm plot for Pb onto PNAC Carbonized at 600oC and activated with HCl, H3PO4, H2SO4
Figure 4.47: Langmuir Isotherm plot for Pb onto PNAC Carbonized at 800oC and activated with HCl, H3PO4, H2SO4
Figure 4.48: Temkin Isotherm plot for Pb onto PNAC Carbonized at 600oC and activated with HCl, H3PO4, H2SO4
-1 -0.5 0
-0.5 0 0.5 1 1.5 2
Logqe
LogCe
0 1 2 3 4
0 0.5 1 1.5 2 2.5
1/qe
1/Ce
0 2 4 6 8
0 0.5 1 1.5 2 2.5
1/qe
1/Ce
0 0.1 0.2 0.3 0.4 0.5 0.6
-1 -0.5 0 0.5 1 1.5 2
qe(mg/g)
InCe
y = -0.307x - 0.299 R² = 0.657
y = -0.259x - 0.329 R² = 0.571
y = -0.247x - 0.348 R² = 0.727
y = 0.499x + 1.866 R² = 0.464 y = 0.540x + 1.849 R² = 0.691
y = -0.067x + 2.417 R² = 0.009
y = -26.76x + 6.727 R² = 0.726
y = -19.34x + 5.942 R² = 0.507
y = -0.660x + 3.153 R² = 0.646
y = 0.085x + 0.406 R² = 0.816 y = 0.077x + 0.416 R² = 0.638
y = -0.019x + 0.452 R² = 0.030
148
Figure 4.49: Temkin Isotherm plot for Pb onto PNAC Carbonized at 800oC and activated with HCl, H3PO4, H2SO4
Figure 4.50: Dubinin Rudushkevich Isotherm plot for Pb onto PNAC Carbonized at 600oC and activated with HCl, H3PO4, H2SO4
Figure 4.51: Dubinin Rudushkevich Isotherm plot for Pb onto PNAC Carbonized at 800oC and activated with HCl, H3PO4, H2SO4
Figure 4.52: Freundlich Isotherm plot for Cd onto PNAC Carbonized at 600oC and activated with HCl, H3PO4, H2SO4
Figures 4.52 to 4.59 present the adsorption of Cd onto PNAC for both carbonization temperatures and they showed high values for the determination coefficients
0 0.2 0.4 0.6
-1 0 1 2 3 4
qe(mg/g)
InCe
-1.5 -1 -0.5 0
0 2 4 6 8
Inqe
Ԑ2/1M
-2 -1.5 -1 -0.5 0
0 2 4 6 8
Inqe
Ԑ2/1M
-2 -1.5 -1 -0.5 0
0 0.5 1 1.5 2
Logqe
LogCe
y = -0.061x + 0.386 R² = 0.685
y = -0.055x + 0.385 R² = 0.600
y = -0.103x + 0.460 R² = 0.665
y = 0.009x - 0.862 R² = 0.015
y = -0.055x - 0.671 R² = 0.455
y = -0.056x - 0.673 R² = 0.651
y = 4.700x - 1.675 R² = 0.489 y = 7.151x - 1.814 R² = 0.826 y = 0.063x - 1.086 R² = 0.559
y = -2.972x + 3.858 R² = 0.985
y = -3.670x + 4.862 R² = 0.916
y = -2.664x + 3.17 R² = 0.861
149
indicating good fit of the data obtained on the four isotherm models that were tested.
Figure 4.53: Freundlich Isotherm plot for Cd onto PNAC Carbonized at 800oC and activated with HCl, H3PO4, H2SO4
Figure 4.54: Langmuir Isotherm plot for Cd onto PNAC Carbonized at 600oC and activated with HCl, H3PO4, H2SO4
Figure 4.55: Langmuir Isotherm plot for Cd onto PNAC Carbonized at 800oC and activated with HCl, H3PO4, H2SO4
Figure 4.56: Temkin Isotherm plot for Cd onto PNAC Carbonized at 600oC and activated with HCl, H3PO4, H2SO4
-2 -1.5 -1 -0.5 0
0 0.5 1 1.5 2
Logqe
LogCe
-20 0 20 40 60
0 0.01 0.02 0.03 0.04 0.05 0.06
1/qe
1/Ce
-20 0 20 40 60
0 0.05 0.1 0.15 0.2
1/qe
1/Ce
0 0.1 0.2 0.3 0.4
0 1 2 3 4 5
qe(mg/g)
InCe
y = -2.149x + 2.594 R² = 0.816
y = -0.467x + 0.051 R² = 0.891
y = -2.630x + 3.076 R² = 0.918
y = -2393.x + 79.07 R² = 0.675
y = -1203.x + 39.49 R² = 0.966
y = -1134.x + 50.56 R² = 0.521
y = -588.3x + 22.15 R² = 0.713
y = -17.77x + 5.120 R² = 0.707
y = -1181.x + 54.57 R² = 0.641
y = -0.349x + 1.423 R² = 0.998
y = -0.332x + 1.365 R² = 0.989
y = -0.313x + 1.286 R² = 0.990
150
Figure 4.57: Temkin Isotherm plot for Cd onto PNAC Carbonized at 800oC and activated with HCl, H3PO4, H2SO4
Figure 4.58: Dubinin Rudushkevich Isotherm plot for Cd onto PNAC Carbonized at 600oC and activated with HCl, H3PO4, H2SO4
Figure 4.59: Dubinin Rudushkevich Isotherm plot for Cd onto PNAC Carbonized at 800oC &
activated with HCl, H3PO4, H2SO4
Figure 4.60: Freundlich Isotherm plot for Mn onto PNAC Carbonized at 600oC and activated with HCl, H3PO4, H2SO4
For the adsorption of Mn onto PNAC for both carbonization temperatures, the data obtained for the plot of the four isotherm models did not fit well as shown by the R2‘s at both temperatures of carbonization (Figures 4. 60 to 4.67).
0 0.2 0.4 0.6
0 1 2 3 4 5
qe(mg/g)
InCe
-5 -4 -3 -2 -1 0
0 0.005 0.01 0.015
Inqe
Ԑ2/1M
-6 -4 -2 0
0 0.05 0.1 0.15 0.2
Inqe
Ԑ2/1M
-2000 -1500 -1000 -500 0
0 0.5 1 1.5 2 2.5
Logqe
LogCe
y = -0.311x + 1.295 R² = 0.862
y = -0.154x + 0.761 R² = 0.965
y = -0.316x + 1.297 R² = 0.993
y = 477.0x - 4.351 R² = 0.861 y = 433.4x - 3.773 R² = 0.987 y = 190.4x - 3.393 R² = 0.648
y = 213.4x - 3.652 R² = 0.8
y = 5.123x - 1.534 R² = 0.840 y = 256.4x - 2.942 R² = 0.747
y = 0.356x - 0.749 R² = 0.297 y = 237.4x - 793.2 R² = 0.006
y = -0.526x + 0.534 R² = 0.365
151
Figure 4.61: Freundlich Isotherm plot for Mn onto PNAC Carbonized at 800oC and activated with HCl, H3PO4, H2SO4
Figure 4.62: Langmuir Isotherm plot for Mn onto PNAC Carbonized at 600oC and activated with HCl, H3PO4, H2SO4
Figure 4.63: Langmuir Isotherm plot for Mn onto PNAC Carbonized at 800oC and activated with HCl, H3PO4, H2SO4
Figure 4.64: Temkin Isotherm plot for Mn onto PNAC Carbonized at 600oC and activated with HCl, H3PO4, H2SO4
-1.2 -1 -0.8 -0.6 -0.4 -0.2 0 0.2
0 0.5 1 1.5 2 2.5
Logqe
LogCe
0 2 4 6 8
0 0.005 0.01 0.015 0.02 0.025 0.03 0.035
1/qe
1/Ce
0 5 10 15
0 0.02 0.04 0.06 0.08 0.1
1/qe
1/Ce
0 0.2 0.4 0.6 0.8 1
0 1 2 3 4 5 6
qe(mg/g)
InCe
y = -1.052x + 1.437 R² = 0.639
y = -0.579x + 0.658 R² = 0.526
y = -0.597x + 0.672 R² = 0.425
y = -100.6x + 4.6 R² = 0.247 y = 32.12x + 0.744 R² = 0.414
y = -56.10x + 3.566 R² = 0.293
y = -238.4x + 8.378 R² = 0.509
y = -52.89x + 3.765 R² = 0.335
y = -52.32x + 4.898 R² = 0.201
y = -0.160x + 1.069 R² = 0.334
y = -0.155x + 1.095 R² = 0.310
y = 0.205x - 0.069 R² = 0.257
152
Figure 4.65: Temkin Isotherm plot for Mn onto PNAC Carbonized at 800oC and activated with HCl, H3PO4, H2SO4
Figure 4.66: Dubinin Rudushkevich Isotherm plot for Mn onto PNAC Carbonized at 600oC and activated with HCl, H3PO4, H2SO4
Figure 4.67: Dubinin Rudushkevich Isotherm plot for Mn onto PNAC Carbonized at 800oC and activated with HCl, H3PO4, H2SO4
Figure 4.68: Freundlich Isotherm plot for Ni onto PKAC Carbonized at 600oC and activated with HCl, H3PO4, H2SO4
0 0.2 0.4 0.6 0.8 1
0 1 2 3 4 5 6
qe(mg/g)
InCe
-2 -1.5 -1 -0.5 0
0 0.001 0.002 0.003 0.004 0.005 0.006 0.007
Inqe
Ԑ2/1M
-3 -2 -1 0
0 0.01 0.02 0.03 0.04 0.05
Inqe
Ԑ2/1M
-3 -2 -1 0
0 0.5 1 1.5 2
Logqe
LogCe
y = -0.213x + 1.349 R² = 0.467
y = -0.291x + 1.638 R² = 0.536
y = -0.200x + 1.380 R² = 0.381
y = 98.33x - 1.215 R² = 0.129 y = 52.56x - 1.027 R² = 0.113
y = -73.62x - 0.104 R² = 0.469
y = 178.1x - 1.583 R² = 0.287 y = 14.04x - 0.859 R² = 0.079 y = 47.90x - 1.060 R² = 0.170
y = -0.487x + 0.176 R² = 0.837
y = -1.878x + 2.221 R² = 0.862
y = -3.287x + 4.371 R² = 0.276
153
Figure 4.69: Freundlich Isotherm plot for Ni onto PKAC Carbonized at 800oC and activated with HCl, H3PO4, H2SO4
Figure 4.70: Langmuir Isotherm plot for Ni onto PKAC Carbonized at 600oC & activated with HCl, H3PO4, H2SO4
Figure 4.71: Langmuir Isotherm plot for Ni onto PKAC Carbonized at 800oC and activated with HCl, H3PO4, H2SO4
Figure 4.72: Temkin Isotherm plot for Ni onto PKAC Carbonized at 600oC and activated with HCl, H3PO4, H2SO4
-2 -1.5 -1 -0.5 0
0 0.5 1 1.5 2
Logqe
LogCe
0 5 10 15 20
0 0.05 0.1 0.15
1/qe
1/Ce
0 10 20 30 40
0 0.02 0.04 0.06 0.08 0.1
1/qe
1/Ce
0 0.2 0.4 0.6
0 1 2 3 4 5
qe(mg/g)
InCe
y = -1.121x + 1.061 R² = 0.945
y = -0.691x + 0.362 R² = 0.727
y = -2.222x + 2.686 R² = 0.829
y = -18.61x + 4.108 R² = 0.540
y = -690.2x + 24.78 R² = 0.740
y = -488.5x + 19.49 R² = 0.635
y = -221.3x + 11.57 R² = 0.941
y = -76.88x + 8.167 R² = 0.607
y = -999.9x + 39.24 R² = 0.497
y = -0.167x + 0.867 R² = 0.845
y = -0.112x + 0.548 R² = 0.692
y = -0.249x + 1.097 R² = 0.884
154
The determination coefficients for the adsorption of Ni onto PKAC were generally high indicating a good fit of the adsorption data on the Temkin isotherm model (Figures 4.72 and 4.73). A similar result was also obtained for Pb and Cd. For Mn adsorption, the R2 values were all very low indicating a poor fit of the data onto the model except for that carbonized at 600oC and activated with HCl.
Figure 4.73: Temkin Isotherm plot for Ni onto PKAC Carbonized at 800oC and activated with HCl, H3PO4, H2SO4
Figure 4.74: Dubinin Rudushkevich Isotherm plot for Ni onto PKAC Carbonized at 600oC and activated with HCl, H3PO4, H2SO4
Figure 4.75: Dubinin Rudushkevich Isotherm plot for Ni onto PKAC Carbonized at 800oC and activated with HCl, H3PO4, H2SO4
0 0.2 0.4 0.6
0 1 2 3 4 5
qe(mg/g)
InCe
-3 -2 -1 0
0 0.02 0.04 0.06 0.08 0.1 0.12
Inqe
Ԑ2/1M
-4 -3 -2 -1 0
0 0.01 0.02 0.03 0.04 0.05
Inqe
Ԑ2/1M
y = -0.220x + 1.009 R² = 0.919
y = -0.190x + 0.924 R² = 0.875
y = -0.276x + 1.202 R² = 0.935
y = 5.804x - 1.196 R² = 0.461 y = 276.9x - 2.956 R² = 0.795 y = 191.8x - 2.72 R² = 0.628
y = 249.9x - 3.209 R² = 0.608 y = 25.69x - 1.744 R² = 0.580 y = 124.9x - 2.250 R² = 0.897
155
Figure 4.76: Freundlich Isotherm plot for Pb onto PKAC Carbonized at 600oC and activated with HCl, H3PO4, H2SO4
Figure 4.77: Freundlich Isotherm plot for Pb onto PKAC Carbonized at 800oC and activated with HCl, H3PO4, H2SO4
Figure 4.78: Langmuir Isotherm plot for Pb onto PKAC Carbonized at 600oC and activated with HCl, H3PO4, H2SO4
Figure 4.79: Langmuir Isotherm plot for Pb onto PKAC Carbonized at 800oC and activated with HCl, H3PO4, H2SO4
-1 -0.8 -0.6 -0.4 -0.2 0
-0.5 0 0.5 1 1.5 2
Logqe
LogCe
-0.8 -0.6 -0.4 -0.2 0
0 0.5 1 1.5 2
Logqe
LgoCe
0 2 4 6 8
0 0.5 1 1.5 2 2.5
1/qe
1/Ce
0 2 4 6
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
1/qe
1/Ce
y = 0.161x - 0.973 R² = 0.134
y = -0.035x - 0.503 R² = 0.441
y = 0.143x - 0.415 R² = 0.989
y = 0.132x - 0.598 R² = 0.858 y = 0.085x - 0.497 R² = 0.405
y = -0.179x - 0.366 R² = 0.801
y = 15.18x + 5.002 R² = 0.065
y = -1.434x + 3.628 R² = 0.417
y = 0.492x + 1.983 R² = 0.906
y = 3.119x + 2.558 R² = 0.782
y = -5.674x + 4.392 R² = 0.535
y = 0.559x + 2.569 R² = 0.141
156
Figure 4.80: Temkin Isotherm plot for Pb onto PKAC Carbonized at 600oC and activated with HCl, H3PO4, H2SO4
Figure 4.81: Temkin Isotherm plot for Pb onto PKAC Carbonized at 800oC and activated with HCl, H3PO4, H2SO4
Figure 4.82: Dubinin Rudushkevich Isotherm plot for Pb onto PKAC Carbonized at 600oC and activated with HCl, H3PO4, H2SO4
The adsorption data for Ni, Pb, Mn and Cd onto PKAC, generally did not followed the Dubinin Rudushkevich isotherm model having had relatively Low determination coefficient values in almost all the adsorption plots (Figures 4.73, 4.74, 4.81, 4.82, 4.89, 4.90).
0 0.2 0.4 0.6
-1 0 1 2 3 4
qe(mg/g)
InCe
-20 0 20 40 60
0 1 2 3 4
qe(mg/g)
InCe
-2 -1.5 -1 -0.5 0
0 2 4 6 8
Inqe
Ԑ2/1M y = -3.808x - 1.675
R² = 0.032 y = 0.365x - 1.274 R² = 0.376
y = -0.050x - 0.729 R² = 0.821
y = 0.045x + 0.237 R² = 0.842
y = -0.047x + 0.396 R² = 0.836
y = 10.56x - 11.45 R² = 0.303
y = 0.030x + 0.082 R² = 0.143 y = -0.01x + 0.312 R² = 0.441 y = 0.061x + 0.386 R² = 0.987
157
Figure 4.83: Dubinin Rudushkevich Isotherm plot for Pb onto PKAC Carbonized at 800oC and activated with HCl, H3PO4, H2SO4
Figure 4.84: Freundlich Isotherm plot for Cd onto PKAC Carbonized at 600oC and activated with HCl, H3PO4, H2SO4
Figure 4.85: Freundlich Isotherm plot for Cd onto PKAC Carbonized at 800oC and activated with HCl, H3PO4, H2SO4
Figure 4.86: Langmuir Isotherm plot for Cd onto PKAC Carbonized at 600oC and activated with HCl, H3PO4, H2SO4
-2 0 2 4
0 0.5 1 1.5 2
Inqe
Ԑ2/1M
-2 -1.5 -1 -0.5 0
0 0.5 1 1.5 2
Logqe
LogCe
-2 -1.5 -1 -0.5 0
0 0.5 1 1.5 2
Logqe
LogCe
-20 0 20 40 60
0 0.2 0.4 0.6 0.8 1
1/qe
1/Ce
y = -0.680x + 2.357 R² = 0.512
y = -3.337x + 2.657 R² = 0.935
y = -1885.x + 69.39 R² = 0.684
y = -0.113x - 0.234 R² = 0.817
y = -1.263x + 0.735 R² = 0.941
y = 0.614x - 1.528 R² = 0.136
y = -0.112x - 0.252 R² = 0.859
y = -0.158x - 0.200 R² = 0.976
y = -3.276x + 4.180 R² = 0.928
y = -0.728x - 0.998 R² = 0.674
y = -1.114x + 0.347 R² = 0.105
y = 0.872x - 1.399 R² = 0.419
158
Figure 4.87: Langmuir Isotherm plot for Cd onto PKAC Carbonized at 800oC and activated with HCl, H3PO4, H2SO4
Figure 4.88: Temkin Isotherm plot for Cd onto PKAC Carbonized at 600oC and activated with HCl, H3PO4, H2SO4
Figure 4.89: Temkin Isotherm plot for Cd onto PKAC Carbonized at 800oC and activated with HCl, H3PO4, H2SO4
Figure 4.90: Dubinin Rudushkevich Isotherm plot for Cd onto PKAC Carbonized at 600oC and activated with HCl, H3PO4, H2SO4
-20 0 20 40 60
0 0.05 0.1 0.15 0.2 0.25
1/qe
1/Ce
0 0.2 0.4 0.6
0 1 2 3 4 5
qe(mg/g)
InCe
0 0.2 0.4 0.6 0.8
0 1 2 3 4 5
qe(mg/g)
InCe
-5 -4 -3 -2 -1 0
0 0.5 1 1.5 2 2.5 3
Inqe
Ԑ2/1M y = 0.087x - 0.803
R² = 0.392 y = 1.183x - 0.916 R² = 0.890 y = 376.8x - 4.144 R² = 0.873 y = -0.050x + 0.566 R² = 0.816
y = 0.291x - 0.161 R² = 0.302 y = 0.087x - 0.044 R² = 0.012
y = -0.050x + 0.552 R² = 0.879
y = -0.069x + 0.598 R² = 0.976
y = -0.343x + 1.400 R² = 0.996
y = -2.081x + 2.452 R² = 0.714
y = -150.4x + 26.49 R² = 0.618
y = -1789.x + 61.82 R² = 0.417
159
Figure 4.91: Dubinin Rudushkevich Isotherm plot for Cd onto PKAC Carbonized at 800oC and activated with HCl, H3PO4, H2SO4
Figure 4.92: Freundlich Isotherm plot for Mn onto PKAC Carbonized at 600oC and activated with HCl, H3PO4, H2SO4
Figure 4.93: Freundlich Isotherm plot for Mn onto PKAC Carbonized at 600oC and activated with HCl, H3PO4, H2SO4
Figure 4.94: Langmuir Isotherm plot for Mn onto PKAC Carbonized at 600oC and activated with HCl, H3PO4, H2SO4
-6 -4 -2 0
0 0.05 0.1 0.15 0.2 0.25 0.3
Inqe
Ԑ2/1M
-0.4 -0.2 0 0.2
-0.5 0 0.5 1 1.5 2 2.5
Logqe
LogCe
-1 -0.5 0
0 0.5 1 1.5 2 2.5
Logqe
LogCe
0 0.5 1 1.5 2 2.5
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6
1/qe
1/Ce
y = 4.614x + 1.969 R² = 0.203
y = -6.681x + 1.794 R² = 0.191
y = 0.271x + 0.947 R² = 0.972 y = -0.348x + 0.243 R² = 0.342
y = -0.144x + 0.035 R² = 0.177
y = -0.473x + 0.330 R² = 0.452
y = 0.049x - 0.400 R² = 0.208
y = -0.144x + 0.035 R² = 0.177
y = 0.090x - 0.113 R² = 0.980
y = 0.666x - 0.845 R² = 0.622 y = 8.348x - 2.127 R² = 0.385 y = 206.4x - 2.723 R² = 0.134
160
Figure 4.95: Langmuir Isotherm plot for Mn onto PKAC Carbonized at 800oC and activated with HCl, H3PO4, H2SO
Figure 4.96: Temkin Isotherm plot for Mn onto PKAC Carbonized at 600oC and activated with HCl, H3PO4, H2SO4
Figure 4.97: Temkin Isotherm plot for Mn onto PKAC Carbonized at 800oC & activated with HCl, H3PO4, H2SO4
Figure 4.98: Dubinin Rudushkevich Isotherm plot for Mn onto PKAC Carbonized at 600oC and activated with HCl, H3PO4, H2SO4
-5 0 5 10 15
0 0.05 0.1 0.15 0.2
1/qe
1/Ce
0 0.5 1 1.5
-1 0 1 2 3 4 5
qe(mg/g)
InCe
0 0.2 0.4 0.6 0.8
0 1 2 3 4 5 6
qe(mg/g)
InCe
y = -0.067x + 0.044 R² = 0.955 y = -8.112x - 0.696
R² = 0.187 y = 5.497x - 0.468
R² = 0.080 -1
-0.5 0 0.5
0 1 2 3 4 5 6
Inqe
Ԑ2/1M y = -8.112x - 0.696
R² = 0.187 y = 5.497x - 0.468 R² = 0.080
y = -0.067x + 0.044 R² = 0.955
y = -0.139x + 1.006 R² = 0.298
y = -0.271x + 1.550 R² = 0.571
y = -0.078x + 0.504 R² = 0.373
y = 0.024x + 0.386 R² = 0.200
y = -0.124x + 1.153 R² = 0.311
y = 0.080x + 0.773 R² = 0.975 y = 16.19x + 1.909 R² = 0.122
y = -164.5x + 8.667 R² = 0.413
y = -23.99x + 4.240 R² = 0.311
161
Figure 4.99: Dubinin Rudushkevich Isotherm plot for Mn onto PKAC Carbonized at 800oC and activated with HCl, H3PO4, H2SO4
Figure 4.100: Freundlich Isotherm plot for Ni onto SSAC Carbonized at 600oC and activated with HCl, H3PO4, H2SO4
Figure 4.101: Freundlich Isotherm plot for Ni onto SSAC Carbonized at 800oC and activated with HCl, H3PO4, H2SO4
Figure 4.102: Langmuir Isotherm plot for Ni onto SSAC Carbonized at 600oC and activated with HCl, H3PO4, H2SO4
-3 -2 -1 0
0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16
Inqe
Ԑ2/1M
-2.5 -2 -1.5 -1 -0.5 0
1.65 1.7 1.75 1.8 1.85
Logqe
LogCe
-2 -1.5 -1 -0.5 0
1.6 1.65 1.7 1.75 1.8 1.85
Logqe
LogCe
0 50 100 150
0 0.005 0.01 0.015 0.02 0.025
1/qe
1/Ce
y = -4603.x + 126.8 R² = 0.073
y = -1429.x + 46.75 R² = 0.259
y = -10041x + 222.1 R² = 0.551
y = -1.832x + 1.847 R² = 0.175
y = 2.648x - 5.995 R² = 0.455
y = -3.636x + 4.919 R² = 0.927
y = -0.934x + 0.285 R² = 0.098
y = -1.440x + 0.944 R² = 0.057
y = -4.309x + 6.011 R² = 0.710
y = 64.22x - 1.052 R² = 0.123 y = 72.36x - 1.532 R² = 0.231 y = 2.500x - 1.208 R² = 0.041