Chapter 8 127 Bi-Functionalized Hybrid Materials as Novel Adsorbents for Heavy Metal
3. Results and discussion 1 Adsorption isotherms
3.3 Effect of contact time and amount of adsorbent
In the process of solid-liquid adsorption, it is convenient to know the necessary contact time between the adsorbent and the adsorbate to achieve a maximum inter- action between both and get removed as much metal ions as possible. Figures 4–6 show the adsorption curves of each metal ion, where it is observed that about 10 h after the start of the process, the adsorption speed is high and that after this time the rate of removal of the ions. It decays, probably, because the sites where the capture of the ions is carried out are saturated, and therefore the balance is reached regardless of the concentration of absorber that has been used. This type of behav- ior is common among various adsorbent materials [37]. Also, it is observed that the adsorption capacity of the adsorbent material decreases significantly with the
Models Parameters
15°C 30°C 45°C
SIPS
KS 0.0470 0.0208 0.0117
qm 23.8607 30.1446 41.8104
nS 1.1294 0.8178 0.9105
R2 0.9895 0.9958 0.9895
Redlich-Peterson
KR 0.1884 0.4259 0.3462
aR 0.0073 0.0326 0.0089
β 1.0 0.8886 1.0
R2 0.9980 0.9953 0.9891
Langmuir
KL 0.0073 0.0089 0.0124
qm 25.6863 26.5263 39.0000
R2 0.9980 0.9933 0.9891
RL 0.121–0.578 0.101–0.529 0.075–0.447
Freundlich
KF 1.3457 2.2983 2.1685
n 2.2770 2.6411 2.2291
R2 0.9723 0.9773 0.9753
RL
Temkin
A 2.0398 × 10−8 1.8935 × 10−8 4.696 × 10−8
B 2.8230 3.3781 −6.3526 × 10−6
R2 0.8390 0.9084 0.4984
Table 3.
Equilibrium parameters of adsorption models at different temperatures for Co ions.
Water Chemistry
3.2 Effect of temperature on the removal of metal ions
In the literature it has been widely reported that one of the most important variables in the process of solid-liquid removal is temperature, since it directly influences some thermodynamic parameters (Table 5) of great interest in the removal process. The negative values of ΔG indicate that the removal processes of the metal ions of the aqueous solutions are carried out spontaneously; the increase of the value in the negative scale parallel to the increase of the temperature shows the direct dependence with this variable. The positive value of the ΔS indicates that the sites of the solid-liquid interface during the uptake of metal ions increase due to the randomness in the adsorbent [4, 5, 13, 34, 37], while the positive value of ΔH reveals that the process has an endothermic nature, which will influence the increase in ion removal as the temperature increases, which makes the process feasible and spontaneous at temperatures above room temperature [27, 36, 37].
Several reports indicate that the metal adsorption process in brushite is spontane- ous; however, some authors indicate that the heat of adsorption in this process is negative, therefore, as the temperature increases, the removal capacity decreases.
Models Parameters
15°C 30°C 45°C
SIPS
KS 0.005 0.016 0.0020
qm 18.2426 20.6152 22.4789
nS 1.1611 0.8644 1.3671
R2 0.9969 0.9985 0.9974
Redlich-Peterson
KR 0.0191 0.2423 0.2024
aR 0.007 0.0240 0.0078
β 1.0 0.9046 1.0
R2 0.9943 0.9990 0.9913
Langmuir
KL 0.0007 0.0078 0.0105
qm 27.7198 18.9551 25.9445
R2 0.9962 0.9975 0.9913
RL 0.588–0.935 0.114–0.562 0.087–0.488
Freundlich
KF 0.0552 1.6384 1.5515
n 1.2921 2.7263 2.3854
R2 0.9923 0.9869 0.9980
Temkin
A 1.873 × 10−8 2.683 × 10−8 2.3779 × 10−10
B 1.0213 2.3617 2.8940
R2 0.6402 0.9078 0.8337
Table 2.
Equilibrium parameters of adsorption models at different temperatures for Ni ions.
The Use of Industrial Waste for the Bioremediation of Water Used in Industrial Processes DOI: http://dx.doi.org/10.5772/intechopen.86803
[4, 5, 13], However, other authors agree with that found in this work, where the heat of adsorption is positive and, as the temperature of the process increases, the adsorption of the ions in the material increases [32].
3.3 Effect of contact time and amount of adsorbent
In the process of solid-liquid adsorption, it is convenient to know the necessary contact time between the adsorbent and the adsorbate to achieve a maximum inter- action between both and get removed as much metal ions as possible. Figures 4–6 show the adsorption curves of each metal ion, where it is observed that about 10 h after the start of the process, the adsorption speed is high and that after this time the rate of removal of the ions. It decays, probably, because the sites where the capture of the ions is carried out are saturated, and therefore the balance is reached regardless of the concentration of absorber that has been used. This type of behav- ior is common among various adsorbent materials [37]. Also, it is observed that the adsorption capacity of the adsorbent material decreases significantly with the
Models Parameters
15°C 30°C 45°C
SIPS
KS 0.0470 0.0208 0.0117
qm 23.8607 30.1446 41.8104
nS 1.1294 0.8178 0.9105
R2 0.9895 0.9958 0.9895
Redlich-Peterson
KR 0.1884 0.4259 0.3462
aR 0.0073 0.0326 0.0089
β 1.0 0.8886 1.0
R2 0.9980 0.9953 0.9891
Langmuir
KL 0.0073 0.0089 0.0124
qm 25.6863 26.5263 39.0000
R2 0.9980 0.9933 0.9891
RL 0.121–0.578 0.101–0.529 0.075–0.447
Freundlich
KF 1.3457 2.2983 2.1685
n 2.2770 2.6411 2.2291
R2 0.9723 0.9773 0.9753
RL
Temkin
A 2.0398 × 10−8 1.8935 × 10−8 4.696 × 10−8
B 2.8230 3.3781 −6.3526 × 10−6
R2 0.8390 0.9084 0.4984
Table 3.
Equilibrium parameters of adsorption models at different temperatures for Co ions.
Water Chemistry
Metal T (K) -ΔG (kJ/mol) ΔH (kJ/mol) ΔS (kJ/mol K)
Ni 288.15 18.52 69.63 308.53
303.15 25.56
318.15 27.62
Co 288.15 24.15 13.39 130.08
303.15 25.91
318.15 28.07
Cu 288.15 20.20 131.74 572.27
303.15 ND
318.15 36.02
Table 5.
Thermodynamic parameters for the equilibrium adsorption process of Ni, Co, and Cu ions.
Models Parameters
15°C 30°C 45°C
SIPS
KS 1.396 × 10−5 ND 0.2080
qm 41.4493 41.3266
nS 2.3971 1.1676
R2 0.9980 0.9200
Redlich-Peterson
KR 0.2036 ND 9.9421
aR 0.0013 0.2322
β 1.0 1.0
R2 0.9632 0.9170
Langmuir
KL 0.0013 ND 0.2322
qm 154.8825 42.8164
R2 0.9632 0.9170
RL 0.435–0.885 0.004–0.041
Freundlich
KF 0.2914 ND 14.5249
n 1.1274 4.7001
R2 0.9548 0.7741
Temkin
A 2.9527 × 10−8 ND 10.1004
B 4.5983 6.7337
R2 0.5789 0.8472
Table 4.
Equilibrium parameters of adsorption models at different temperatures for Cu ions.
The Use of Industrial Waste for the Bioremediation of Water Used in Industrial Processes DOI: http://dx.doi.org/10.5772/intechopen.86803
increase in the concentration of absorbent independent of the temperature at which the removal process is carried out, so that the adsorption potential of the Ni ions decreases from 25.8 to 7.78 mg/g at 15°C, while at 30 and 45°C, it decreases from 20.6 to 7.78 and 20.6 to 8.6 mg/g, respectively. In the case of Co ions, the adsorption capacity decreases from 28.4 to 10.4 mg/g, from 31.04 to 11.97 mg/g, and from 31.04 to 10.4 mg/g at 15, 30, and 45°C, respectively. Finally, in the case of Cu ions, the decrease in the adsorption capacity at 15, 30, and 45°C was 49.9–11.0, 56.8–12.4, and 61.2–12 mg/g, respectively. This type of behavior is observed in the adsorption of metals [1, 26, 28, 29].
In the aqueous solutions with the three metal ions present, a behavior similar to that observed in the solutions prepared with a single metal compound was observed; however, the time necessary to reach equilibrium was around 5 h, and the adsorption capacity of the ions in solution was also significantly decreased by increasing the concentration of sorbent in the solution. The adsorption capacity achieved (Figure 7), for Ni ions, was from 32.4 to 6.2 mg/g, for Co ions from 41.9 to 10 mg/g, and for Cu ions from 59.9 to 12.1 mg/g at 45°C, which indicates that
Figure 4.
Behavior of the removal of Ni ions at different temperatures and concentrations of adsorbent: (a) 15, (b) 30 and (c) 45°C.
Figure 5.
Behavior of the removal of Co ions at different temperatures and concentrations of adsorbent: (a) 15, (b) 30 and (c) 45°C.
Figure 6.
Behavior of the removal of Cu ions at different temperatures and concentrations of adsorbent: (a) 15, (b) 30 and (c) 45°C.
Water Chemistry
Metal T (K) -ΔG (kJ/mol) ΔH (kJ/mol) ΔS (kJ/mol K)
Ni 288.15 18.52 69.63 308.53
303.15 25.56
318.15 27.62
Co 288.15 24.15 13.39 130.08
303.15 25.91
318.15 28.07
Cu 288.15 20.20 131.74 572.27
303.15 ND
318.15 36.02
Table 5.
Thermodynamic parameters for the equilibrium adsorption process of Ni, Co, and Cu ions.
Models Parameters
15°C 30°C 45°C
SIPS
KS 1.396 × 10−5 ND 0.2080
qm 41.4493 41.3266
nS 2.3971 1.1676
R2 0.9980 0.9200
Redlich-Peterson
KR 0.2036 ND 9.9421
aR 0.0013 0.2322
β 1.0 1.0
R2 0.9632 0.9170
Langmuir
KL 0.0013 ND 0.2322
qm 154.8825 42.8164
R2 0.9632 0.9170
RL 0.435–0.885 0.004–0.041
Freundlich
KF 0.2914 ND 14.5249
n 1.1274 4.7001
R2 0.9548 0.7741
Temkin
A 2.9527 × 10−8 ND 10.1004
B 4.5983 6.7337
R2 0.5789 0.8472
Table 4.
Equilibrium parameters of adsorption models at different temperatures for Cu ions.
The Use of Industrial Waste for the Bioremediation of Water Used in Industrial Processes DOI: http://dx.doi.org/10.5772/intechopen.86803
increase in the concentration of absorbent independent of the temperature at which the removal process is carried out, so that the adsorption potential of the Ni ions decreases from 25.8 to 7.78 mg/g at 15°C, while at 30 and 45°C, it decreases from 20.6 to 7.78 and 20.6 to 8.6 mg/g, respectively. In the case of Co ions, the adsorption capacity decreases from 28.4 to 10.4 mg/g, from 31.04 to 11.97 mg/g, and from 31.04 to 10.4 mg/g at 15, 30, and 45°C, respectively. Finally, in the case of Cu ions, the decrease in the adsorption capacity at 15, 30, and 45°C was 49.9–11.0, 56.8–12.4, and 61.2–12 mg/g, respectively. This type of behavior is observed in the adsorption of metals [1, 26, 28, 29].
In the aqueous solutions with the three metal ions present, a behavior similar to that observed in the solutions prepared with a single metal compound was observed; however, the time necessary to reach equilibrium was around 5 h, and the adsorption capacity of the ions in solution was also significantly decreased by increasing the concentration of sorbent in the solution. The adsorption capacity achieved (Figure 7), for Ni ions, was from 32.4 to 6.2 mg/g, for Co ions from 41.9 to 10 mg/g, and for Cu ions from 59.9 to 12.1 mg/g at 45°C, which indicates that
Figure 4.
Behavior of the removal of Ni ions at different temperatures and concentrations of adsorbent: (a) 15, (b) 30 and (c) 45°C.
Figure 5.
Behavior of the removal of Co ions at different temperatures and concentrations of adsorbent: (a) 15, (b) 30 and (c) 45°C.
Figure 6.
Behavior of the removal of Cu ions at different temperatures and concentrations of adsorbent: (a) 15, (b) 30 and (c) 45°C.
Water Chemistry
it is not necessary to saturate the solution with nDCPD to achieve greater metal uptake [32–34]. On the other hand, in the analysis of the Co-Cu binary solution, a behavior similar to the previous cases was observed, achieving a greater adsorp- tion capacity with less amount of absorbent, so that at a temperature of 45°C (Figure 8), for Co ions, it was possible to adsorb 32–9.9 mg/g and for Cu ions from 57 to 11.8 mg/g.
In the removal of ions in solutions, it was observed that the percentage of removal increases with the increase in the amount of nDCPD used, achieving removal percentages close to 100% for Cu ions and 95% for Co ions; however, for Ni about 70% removal was only achieved (Figure 9), suggesting that sites available for nickel capture are quickly saturated due to the large amount of chromium in the effluent. The changes caused by the variation of the temperature depend on the metal ion, since the maximum removal of the Ni ions is between 15 and 30°C, while for the Cu and Co ions, it is given at 30°C. Similar observations have been reported in adsorption studies conducted with other biomaterials [29, 38]. The selectivity shown in the present study was the following: Cu > Co > Ni, with percentages of removal in solutions composed of the three ions of 96% (Cu), 83% (Co), and 59%
(Ni). Additionally, in Figure 10, it is observed that in the solutions composed only by Co or Cu, the time necessary to reach the equilibrium decreases considerably; in addition, the selectivity is maintained toward the removal of Cu compared to the Co, having a percentage of removal of 95–79%, respectively. Finally, the changes caused by the variation of the temperature depend on the metal ion, since the maximum removal of the Ni ions is between 15 and 30°C, while for the Cu and Co ions, it was at 30°C (Figure 11).