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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.

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Adsorption capacity (qt) of cadmium by CAB at different temperatures (°C) versus time (min).
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fig1: Adsorption capacity (qt) of cadmium by CAB at different temperatures (°C) versus time (min).

Mentions: Figures 1 and 2 show the results obtained from the tests of cadmium and lead removal by CAB at different temperatures and as a function of time, respectively. The curves of cadmium removal are characterized by a relatively fast sorption in the first 60 minutes of contact time at all temperatures (Figure 1). During the first two hours of contact time, 8.5 mg/g of the sorption occurred, and the equilibrium was reached. A total cadmium removal from the aqueous solution, near 100%, was observed at 50°C. In the case of lead removal by CAB in the same experimental conditions, the kinetic sorption behavior was different to Figure 2 since maximum adsorption of Pb is reached in the first minutes of reaction at 35 and 50°C. Additionally, at 25°C the maximum adsorption of Pb was obtained after 3 h. During the first two hours of contact time, 15.9 mg/g of lead sorption occurred, and the equilibrium was reached. A total removal of the lead from the aqueous solution, near 100%, was observed at 35 and 50°C. From these data, it can be observed that temperature plays an important role in the kinetics of cadmium and lead removal by this biosorbent.


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).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig1: Adsorption capacity (qt) of cadmium by CAB at different temperatures (°C) versus time (min).
Mentions: Figures 1 and 2 show the results obtained from the tests of cadmium and lead removal by CAB at different temperatures and as a function of time, respectively. The curves of cadmium removal are characterized by a relatively fast sorption in the first 60 minutes of contact time at all temperatures (Figure 1). During the first two hours of contact time, 8.5 mg/g of the sorption occurred, and the equilibrium was reached. A total cadmium removal from the aqueous solution, near 100%, was observed at 50°C. In the case of lead removal by CAB in the same experimental conditions, the kinetic sorption behavior was different to Figure 2 since maximum adsorption of Pb is reached in the first minutes of reaction at 35 and 50°C. Additionally, at 25°C the maximum adsorption of Pb was obtained after 3 h. During the first two hours of contact time, 15.9 mg/g of lead sorption occurred, and the equilibrium was reached. A total removal of the lead from the aqueous solution, near 100%, was observed at 35 and 50°C. From these data, it can be observed that temperature plays an important role in the kinetics of cadmium and lead removal by this biosorbent.

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