Environmental Engineering Reference
In-Depth Information
100
90
80
70
60
50
40
30
Cu(II)
Ni(II)
20
10
0
0.001M
0.01M
0.05M
0.1M
0.2M
HCl Concentration
Figure 9.25
Desorption efficiency of adsorbed Cu(II)/Ni(II) by HCl of 0.0010.2M.
9.5.2.7 Desorption Kinetics
For desorption kinetic studies, 40 mL of 0.01 M NaOH and 40 mL of 0.05 M
HCl were used for the desorption of adsorbed Cr and Cu/Ni, respectively. The effect of
contact time on the desorption of Cr(VI), Cu(II) and Ni(II) is shown in Figure 9.26. The
rate of metal desorption decreased gradually till constant after 60 minutes. The
desorption equilibrium time of these three metals was found to be 30 minutes with
defining the value of c/t to be lower than 0.01.
9.5.2.8 Regeneration Studies
Regeneration of adsorbents is commonly accomplished with heat, chemical
change or solvent action. The use of the adsorption system for product recovery is
generally a well understood principle, but not widely practiced due to the technical
limitations. Successive adsorption-desorption processes were carried out within five
cycles. As aforementioned, the first 5 mL of NaOH only can remove 90% of the
adsorbed Cr(VI) from -Fe
2
O
3
nanoparticles, and therefore, some active sites were still
occupied by chromium, resulting in less sites for the next cycle of Cr(VI) adsorption. To
improve the complete desorption of adsorbed Cr(VI), the -Fe
2
O
3
nanoparticles were
separated and then added into another 2 mL of 0.01 M NaOH and shaken for 30 minutes.
Subsequently, the nanoparticles were thoroughly washed with ultrapure water and
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