title: Thermodynamic, kinetic, and equilibrium parameters for the removal of lead and cadmium from aqueous solutions with calcium alginate beads.
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.
authors.affiliation: Instituto de Investigaciones Químico Biológicas, Universidad Michoacana de San Nicolás de Hidalgo, CP 58060, Edif. B1., CU, Morelia, MICH, Mexico.
authors.forename: Ruth
authors.initials: R
authors.lastname: Alfaro-Cuevas-Villanueva
authors.affiliation: Instituto de Investigaciones Químico Biológicas, Universidad Michoacana de San Nicolás de Hidalgo, CP 58060, Edif. B1., CU, Morelia, MICH, Mexico.
authors.forename: Aura Roxana
authors.initials: AR
authors.lastname: Hidalgo-Vázquez
authors.affiliation: Facultad de Químico Farmacobiología, Universidad Michoacana de San Nicolás de Hidalgo, Tzintzuntzan 173 Col. Matamoros, CP 58240, Morelia, MICH, Mexico.
authors.forename: Consuelo de Jesús
authors.initials: Cde J
authors.lastname: Cortés Penagos
authors.affiliation: Facultad de Químico Farmacobiología, Universidad Michoacana de San Nicolás de Hidalgo, Tzintzuntzan 173 Col. Matamoros, CP 58240, Morelia, MICH, Mexico.
authors.forename: Raúl
authors.initials: R
authors.lastname: Cortés-Martínez
mesh_terms: D000464:Alginates / Q000737:chemistry*; D002104:Cadmium / Q000737:chemistry*; D020723:Glucuronic Acid / Q000737:chemistry; D006603:Hexuronic Acids / Q000737:chemistry; D007700:Kinetics; D007854:Lead / Q000737:chemistry*; D008863:Microspheres; D013816:Thermodynamics; D018505:Waste Management / Q000379:methods; D014874:Water Pollutants, Chemical / Q000737:chemistry
chemical_list: D000464:Alginates; D006603:Hexuronic Acids; D014874:Water Pollutants, Chemical; D002104:Cadmium; D007854:Lead; D020723:Glucuronic Acid