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. 2022 Apr 1;7(14):12342-12353.
doi: 10.1021/acsomega.2c00819. eCollection 2022 Apr 12.

Removal of Uranium-238, Thorium-232, and Potassium-40 from Wastewater via Adsorption on Multiwalled Carbon Nanotubes

Saad S M Hassan  1 , Ehab M Abdel Rahman  2 , Gehan M El-Subruiti  3 , Ayman H Kamel  1 , Hanan M Diab  2
Affiliations

Removal of Uranium-238, Thorium-232, and Potassium-40 from Wastewater via Adsorption on Multiwalled Carbon Nanotubes

Saad S M Hassan et al. ACS Omega. .

Abstract

The optimum conditions for the removal of uranium-238, thorium-232, and potassium-40 from wastewater and the discharge of nuclear facilities using multiwalled carbon nanotubes (CNTs) are described. The adsorption mechanism is mainly attributed to chemical interactions between the metal ions and surface functional groups of the CNTs. Batch adsorption experiments are carried out in order to study the effect of different parameters such as pH, contact time, initial metal ion concentration, adsorbent dose, and temperatures. Maximum metal removal (>98%) from solutions containing 20-120 Bq/L metal ions is achieved using a contact time of 15 min, a pH of 6.0, and 10 mg/L CNTs. The effect of temperature on the kinetics and equilibrium of adsorption on CNT particles is examined. Consistent with an exothermic reaction, an increase in the temperature resulted in an increase in the adsorption rate. Langmuir, Freundlich, and Dubinin-Radushkevich isotherms are applied to the data obtained at various temperatures. The Langmuir adsorption model is the best for data interpretations. The kinetics of adsorption reveals a pseudo-second-order mechanism. Thermodynamic parameters at 293 K (ΔG°, ΔH°, and ΔS°) for U-238, Th-232, and K-40 are -14590.7 kJ/mol, -6.66 kJ/mol, and 26.47 J/(mol K), -96,96.5 kJ/mol, -2.48 kJ/mol, and 14.17 J/(mol K), and -3922.09 kJ/mol, -1.32 kJ/mol, and 6.12 J/(mol K), respectively.

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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Figure 1
Figure 1
Effect of pH on qe (mg/g) due to adsorption of uranium-238, thorium-232, and potassium-40 onto MWCNTs (initial metal concentration = 111.6, 23.67, and 77.22 Bq/L, respectively, MWCNT dose = 0.01 g, stirring speed = 600 rpm, T = 293 K, and contact time = 15 min).
Figure 2
Figure 2
Effect of pH for on adsorption of uranium-238, thorium-232, and potassium40 onto MWCNTs (the initial concentration = 111.6 23.67, and 77.22 Bq/L, respectively, MWCNT dose = 0.01 g, stirring speed = 600 rpm, T = 293 K, and contact time = 15 min).
Figure 3
Figure 3
Relationship between qt (mg/g) and time at different concentrations of uranium-238 on 0.01 g of MWCNTs at 600 rpm and 293 K.
Figure 4
Figure 4
Effect of contact time on the adsorption of uranium-238 onto MWCNTs (initial metal concentrations = 27.9, 55.8, and 111.6 Bq/L, MWCNT dose = 0.01 g/L, pH = 6, stirring speed = 600 rpm, contact time 15 min, and T = 293 K).
Figure 5
Figure 5
Relationship between qt (mg/g) and time at different concentrations of thorium-232 on MWCNTs at 600 rpm and 293 K, with 0.01 g of MWCNTs.
Figure 6
Figure 6
Effect of contact time for adsorption of thorium-232 onto MWCNTs (the initial concentration = 5.91, 11.83, and 23.67 Bq/L, MWCNT dose = 0.01 g/L, pH = 6, stirring speed = 600 rpm, contact time = 15 min, and T = 293 K).
Figure 7
Figure 7
Relationship between qt (mg/g) and time at different concentrations of potassium-40 at 600 rpmand 293 K with 0.01 g of MWCNTs.
Figure 8
Figure 8
Effect of contact time for adsorption of potassium-40 onto MWCNTs (the metal concentrations = 77.22, 38.61, and 19.30 Bq/L, carbon nanotube dose = 0.01 g/l, pH = 6.0, stirring speed = 600 rpm, contact time = 15 min, and T = 293 K).
Figure 9
Figure 9
Relation between qt and time at different doses of carbon nanotubes at 600 rpm and 293 K with 111.6 Bq/L initial uranium-238 concentration.
Figure 10
Figure 10
Relation between % removal and time at different doses of carbon nanotubes at 600 rpm, 293 K, and an initial concentration of 111.6 Bq/L of uranium-238.
Figure 11
Figure 11
Relation between qt and time at different doses of MWCNTs at 600 rpm and 293 K with a 23.67 Bq/L initial concentration of thorium-232.
Figure 12
Figure 12
Relation between % removal and contact time at different doses of carbon nanotubes at 600 rpm, 293 K, and an initial concentration of 23.67 Bq/L of thorium-232.
Figure 13
Figure 13
Relation between qt and time at different doses of MWCNTs at 600 rpm, 293 K, and an initial concentration of 77.22 Bq/L of potassium-40.
Figure 14
Figure 14
Relation between % removal and contact time at different doses of MWCNTs at 600 rpm, 293 K, and an initial concentration of 77.22 Bq/L of potassium-40.
Figure 15
Figure 15
Relation between qe and initial concentration of uranium-238.
Figure 16
Figure 16
Relation between qe and initial concentration of thorium-232.
Figure 17
Figure 17
Relation between qe and initial concentration of potassium-40.
Figure 18
Figure 18
Relation between temperature and different initial metal concentrations (111.6, 23.67, and 77.22 Bq/L, respectively) of uranium-238, thorium-232, and potassium-40 mg/g at a 0.01 g/L dose of MWCNTs and 600 rpm.
Figure 19
Figure 19
Relationship between qt and time at different temperatures, initial metal ion concentrations of 111.6, 23.67, and 77.22 Bq/L, a 0.01 g/L dose of MWCNTs, and 600 rpm. (a) Uranium-238; (b) thorium-232; and (c) potassium-40.
Figure 20
Figure 20
Relationship between % metal ion removal and time at different temperatures, at initial concentrations of 111.6, 23.67, and 77.22 Bq/L, a 0.01 g/L dose of MWCNTs, and 600 rpm. (a) Uranium-238; (b) thorium-232; and (c) potassium-40.
Figure 21
Figure 21
Relationship between ln(Ke) and reciprocal of temperature at initial concentrations of 111.6, 23.67, and 77.22 Bq/L for uranium-238, thorium-232, and potassium-40, respectively, a 0.01 g/L dose of MWCNTs, and 600 rpm.
Figure 22
Figure 22
Pseudo-first-order kinetic model for the adsorption of uranium-238 ions onto MWCNTs at different initial metal concentrations, a 0.01 g MWCNT dose, 600 rpm, and 293 K.
Figure 23
Figure 23
Pseudo-first-order kinetic model for the adsorption of thorium-232 ions onto MWCNTs at different initial metal concentrations, a 0.01 g MWCNT dose, 600 rpm, and 293 K.
Figure 24
Figure 24
Pseudo-first-order kinetic model for the adsorption of potassium-40 ions onto carbon nanotubes at different initial metal concentrations, a 0.01 g MWCNT dose, 600 rpm, and 293 K.
Figure 25
Figure 25
Pseudo-second-order kinetic model for the adsorption of uranium-238 onto MWCNTs at different initial metal concentrations, a 0.01 g MWCNT dose, 600 rpm, and 293 K.
Figure 26
Figure 26
Pseudo-second-order kinetic model for the adsorption of thorium-232 ions onto MWCNTs at different initial metal concentrations, a 0.01 g MWCNT dose, 600 rpm, and 293 K.
Figure 27
Figure 27
Pseudo-second-order kinetic model for the adsorption of potassium-40 ions onto MWCNTs at different initial metal concentrations, a 0.01 g MWCNT dose, 600 rpm, and 293 K.
Figure 28
Figure 28
linear Langmuir adsorption isotherms of (a) uranium-238; (b) thorium-232; and (c) potassium-40 onto MWCNTs at 293 K.
Figure 29
Figure 29
Linear Freundlich adsorption isotherms for (a) uranium-238; (b) thorium-232; and (c) potassium-40 onto MWCNTs at 293 K.
Figure 30
Figure 30
D–R adsorption isotherms of (a) uranium-238, (b) thorium-232, and (c) potassium-40 onto MWCNTs at 293 K.
Figure 31
Figure 31
XRD spectra of the MWCNTs before and after adsorption of uranium-238, thorium-232, and potassium-40 metal ions.
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