Research Article Thermodynamic, Kinetic, and Equilibrium Parameters for the Removal of Lead and Cadmium from Aqueous Solutions with Calcium Alginate Beads Ruth Alfaro-Cuevas-Villanueva, 1 Aura Roxana Hidalgo-Vázquez, 1 Consuelo de Jesús Cortés Penagos, 2 and Raúl Cortés-Martínez 2 1 Instituto de Investigaciones Qu´ ımico Biol´ ogicas, Universidad Michoacana de San Nicol´ as de Hidalgo, CP 58060, Edif. B1., CU, Morelia, MICH, Mexico 2 Facultad de Qu´ ımico Farmacobiolog´ ıa, Universidad Michoacana de San Nicol´ as de Hidalgo, Tzintzuntzan 173 Col. Matamoros, CP 58240, Morelia, MICH, Mexico Correspondence should be addressed to Ra´ ul Cort´ es-Mart´ ınez; raulcortesmtz@gmail.com Received 31 August 2013; Accepted 21 October 2013; Published 27 January 2014 Academic Editors: S. Khouf and Y. Xu Copyright © 2014 Ruth Alfaro-Cuevas-Villanueva et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Te sorption of cadmium (Cd) and lead (Pb) by calcium alginate beads (CAB) from aqueous solutions in batch systems was investigated. Te kinetic and thermodynamic parameters, as well as the sorption capacities of CAB in each system at diferent temperatures, were evaluated. Te rate of sorption for both metals was rapid in the frst 10 minutes and reached a maximum in 50 minutes. Sorption kinetic data were ftted 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 ( 2 ) for Pb was observed, indicating that the interaction between lead cations and alginate beads was faster than for cadmium. Similarly, isotherm data were ftted to diferent 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 efect on the adsorption of these metals by CAB, as more were removed at pH values between 6 and 7. 1. Introduction Water, air, and soil pollution by heavy metals is one of the most serious environmental problems and is very difcult to solve [1]. Heavy metal contamination exists in wastewater streams from diferent industries such as electroplating, mining, and tanneries, among others. Some of the met- als associated with these activities are cadmium, copper, chromium, iron, mercury, nickel, lead, and zinc [2]. Tese metals are not biodegradable, and they tend to accumulate in living organisms, causing diseases and disorders. For these reasons, they are considered priority pollutants. Despite the negative efects, these elements are ofen discharged into the environment and reach concentrations above those permitted by law [3]. Heavy metals, such as lead (Pb) and cadmium (Cd), are a sanitary and ecological threat. Tey are highly toxic and recalcitrant even at very low concentrations, and they can pollute drinking water resources. Terefore, research is important to fully understand the systems and technologies needed for their removal [4]. Traditional methods for removing heavy metals, includ- ing chemical precipitation and fltration, redox reactions, electrochemical treatments, reverse osmosis, ion exchange, adsorption, and evaporation [4], generally have several disad- vantages, such as incomplete metal removal, expensive equip- ment and monitoring system requirements, high reagent or energy requirements and the generation of toxic sludge, or other waste products that require disposal. Further, they Hindawi Publishing Corporation e Scientific World Journal Volume 2014, Article ID 647512, 9 pages http://dx.doi.org/10.1155/2014/647512