Use of Carbon Paste Electrode Modified with Biomass for Studying the Equilibria, Kinetics, and Proton Exchange Processes Associated with Bioaccumulation

• Published in: Electroanalysis (New York, N.Y.) N.Y.), 2012-05, Vol.24 (5), p.1121-1128
• Main Authors: Martínez-Sánchez, Carolina, Torres-Rodríguez, Luz María, Velázquez-Jiménez, Litza Halla, Sustaita-Martínez, Jesús Israel, García-de la Cruz, Ramón Fernando
• Format: Article
• Language: English
• Subjects: Biomass; Cadmium; Carbon; Carbon paste electrode; Electrodes; Expulsion; Isotherms; Kinetics; Mathematical models; Pastes; Roots; Sorption
• ISSN: 1040-0397; 1521-4109
• DOI: 10.1002/elan.201200052

The sorption of Cd2+ onto nonliving Typha latifolia roots was investigated using carbon paste electrodes modified with a powder formed from the ground dried root. The equilibria, kinetics, and proton exchange processes associated with the biosorption process were determined. Cd2+ was found to accumulate on the root‐modified electrode under open circuit conditions, and the electrode was transferred to an electrochemical cell for square wave anodic stripping voltammetry measurements. The measured currents were proportional to the amount of Cd2+ adsorbed onto the root, which permitted the biosorption process to be measured as a function of cadmium solution concentration, time, and pH. The equilibrium values were fit to the Langmuir or Freundlich equations, and that the Langmuir isotherm model was found to provide a better fit than the Freundlich model. The pH‐dependent sorption curves showed that the accumulation of cadmium proceeded with proton exchange, and each adsorbed cadmium ion resulted in expulsion of two protons. The sorption kinetics were studied, the data obtained were fit to two models: a pseudo‐second‐order model and an intraparticle diffusion model. The pseudo‐second‐order model provided the best description of the bioadsorption data. These results indicated that these methodologies have clear advantages over existing methods, because the amount of reagents and sorbent used for the experiments are much less than are required for batch experiments.