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Thermodynamic, kinetic, and equilibrium parameters for the removal of lead and cadmium from aqueous solutions with calcium alginate beads.

Alfaro-Cuevas-Villanueva R, Hidalgo-Vázquez AR, Cortés Penagos Cde J, Cortés-Martínez R - ScientificWorldJournal (2014)

Bottom Line: Sorption kinetic data were fitted to Lagergren, pseudo-second-order and Elovich models and it was found that the second-order kinetic model describes these data for the two metals; comparing kinetic parameters for Cd and Pb sorption a higher kinetic rate (K2) for Pb was observed, indicating that the interaction between lead cations and alginate beads was faster than for cadmium.Similarly, isotherm data were fitted to different models reported in literature and it was found that the Langmuir-Freundlich (L-F) and Dubinin-Radushkevich (D-R) models describe the isotherms in all cases.It was also found that pH has an important effect on the adsorption of these metals by CAB, as more were removed at pH values between 6 and 7.

View Article: PubMed Central - PubMed

Affiliation: Instituto de Investigaciones Químico Biológicas, Universidad Michoacana de San Nicolás de Hidalgo, CP 58060, Edif. B1., CU, Morelia, MICH, Mexico.

ABSTRACT
The sorption of cadmium (Cd) and lead (Pb) by calcium alginate beads (CAB) from aqueous solutions in batch systems was investigated. The kinetic and thermodynamic parameters, as well as the sorption capacities of CAB in each system at different temperatures, were evaluated. The rate of sorption for both metals was rapid in the first 10 minutes and reached a maximum in 50 minutes. Sorption kinetic data were fitted to Lagergren, pseudo-second-order and Elovich models and it was found that the second-order kinetic model describes these data for the two metals; comparing kinetic parameters for Cd and Pb sorption a higher kinetic rate (K2) for Pb was observed, indicating that the interaction between lead cations and alginate beads was faster than for cadmium. Similarly, isotherm data were fitted to different models reported in literature and it was found that the Langmuir-Freundlich (L-F) and Dubinin-Radushkevich (D-R) models describe the isotherms in all cases. CAB sorption capacity for cadmium was 27.4 mg/g and 150.4 mg/g for lead, at 25 °C. Sorption capacities of Cd and Pb increase as temperature rises. According to the thermodynamic parameters, the cadmium and lead adsorption process was spontaneous and endothermic. It was also found that pH has an important effect on the adsorption of these metals by CAB, as more were removed at pH values between 6 and 7.

Show MeSH
Adsorption capacity (qt) of cadmium by CAB at different temperatures (°C) versus time (min), adjusted to a pseudo-second-order model.
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Related In: Results  -  Collection


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fig3: Adsorption capacity (qt) of cadmium by CAB at different temperatures (°C) versus time (min), adjusted to a pseudo-second-order model.

Mentions: (4)qt=1bln⁡⁡(1+abt),where qt is the metal concentration at time, t, per weight of adsorbent (mg/g), qe is the concentration of metal removed at equilibrium per weight of adsorbent (mg/g), KL is the pseudo-first-order kinetic constant (min−1), K2 is the pseudo-second-order rate constant of sorption (g/mg·h), and a and b are Elovich constants related to the initial adsorption rate (mg/g·h) and the desorption rate (g/mg), respectively. In general, the experimental data for the sorption of cadmium and lead on CAB, as a function of time, were best fitted to the pseudo-second-order model (Figures 3 and 4), with correlation coefficients (R) between 0.918 and 0.999.


Thermodynamic, kinetic, and equilibrium parameters for the removal of lead and cadmium from aqueous solutions with calcium alginate beads.

Alfaro-Cuevas-Villanueva R, Hidalgo-Vázquez AR, Cortés Penagos Cde J, Cortés-Martínez R - ScientificWorldJournal (2014)

Adsorption capacity (qt) of cadmium by CAB at different temperatures (°C) versus time (min), adjusted to a pseudo-second-order model.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3921947&req=5

fig3: Adsorption capacity (qt) of cadmium by CAB at different temperatures (°C) versus time (min), adjusted to a pseudo-second-order model.
Mentions: (4)qt=1bln⁡⁡(1+abt),where qt is the metal concentration at time, t, per weight of adsorbent (mg/g), qe is the concentration of metal removed at equilibrium per weight of adsorbent (mg/g), KL is the pseudo-first-order kinetic constant (min−1), K2 is the pseudo-second-order rate constant of sorption (g/mg·h), and a and b are Elovich constants related to the initial adsorption rate (mg/g·h) and the desorption rate (g/mg), respectively. In general, the experimental data for the sorption of cadmium and lead on CAB, as a function of time, were best fitted to the pseudo-second-order model (Figures 3 and 4), with correlation coefficients (R) between 0.918 and 0.999.

Bottom Line: Sorption kinetic data were fitted to Lagergren, pseudo-second-order and Elovich models and it was found that the second-order kinetic model describes these data for the two metals; comparing kinetic parameters for Cd and Pb sorption a higher kinetic rate (K2) for Pb was observed, indicating that the interaction between lead cations and alginate beads was faster than for cadmium.Similarly, isotherm data were fitted to different models reported in literature and it was found that the Langmuir-Freundlich (L-F) and Dubinin-Radushkevich (D-R) models describe the isotherms in all cases.It was also found that pH has an important effect on the adsorption of these metals by CAB, as more were removed at pH values between 6 and 7.

View Article: PubMed Central - PubMed

Affiliation: Instituto de Investigaciones Químico Biológicas, Universidad Michoacana de San Nicolás de Hidalgo, CP 58060, Edif. B1., CU, Morelia, MICH, Mexico.

ABSTRACT
The sorption of cadmium (Cd) and lead (Pb) by calcium alginate beads (CAB) from aqueous solutions in batch systems was investigated. The kinetic and thermodynamic parameters, as well as the sorption capacities of CAB in each system at different temperatures, were evaluated. The rate of sorption for both metals was rapid in the first 10 minutes and reached a maximum in 50 minutes. Sorption kinetic data were fitted to Lagergren, pseudo-second-order and Elovich models and it was found that the second-order kinetic model describes these data for the two metals; comparing kinetic parameters for Cd and Pb sorption a higher kinetic rate (K2) for Pb was observed, indicating that the interaction between lead cations and alginate beads was faster than for cadmium. Similarly, isotherm data were fitted to different models reported in literature and it was found that the Langmuir-Freundlich (L-F) and Dubinin-Radushkevich (D-R) models describe the isotherms in all cases. CAB sorption capacity for cadmium was 27.4 mg/g and 150.4 mg/g for lead, at 25 °C. Sorption capacities of Cd and Pb increase as temperature rises. According to the thermodynamic parameters, the cadmium and lead adsorption process was spontaneous and endothermic. It was also found that pH has an important effect on the adsorption of these metals by CAB, as more were removed at pH values between 6 and 7.

Show MeSH