Effects of biosorption parameter: Kinetics, isotherm and thermodynamics for Ni(II) biosorption from aqueous solution by Circinella sp

Circinella sp. was employed as a biosorbent for removal of Ni(II) from aqueous solution. The biosorption kinetics and isotherms were investigated. The effect of several parameters, such as biosorbent dosage, contact time, initial concentration, pH and temperature, on biosorption process was evaluated. The kinetic studies indicated that the biosorption followed pseudo-second order kinetic model. Biosorption behaviour of Ni(II) on Circinella sp. was expressed by both Langmuir and Freundlich isotherms. The equilibrium data fit better to the Langmuir model compared to the Freundlich model in concentration range studied (1.0-3.0 mM). The thermodynamic parameters (?G 0, ?H 0 and ?S 0) were also determined, and it was found that the Ni(II) biosorption by Circinella sp. was spontaneous and endothermic in nature. © 2010 by Pontificia Universidad Católica de Valparaíso, Chile

A novel microbial biosensor based on Circinella sp. modified carbon paste electrode and its voltammetric application

Microbial biosensors have been developed for voltammetric determination of various substances. This paper describes the development of a new biosorption based microbial biosensor for determination of Cu2+. The developed biosensor is based on carbon paste electrode consisting of whole cells of Circinella sp. Cu2+ was preconcentrated on the electrode surface at open circuit and then cathodically detected with the reduction of Cu2+. The voltammetric responses were evaluated with respect to percentage cell loading in the carbon paste, preconcentration time, pH of preconcentration solution, scan rate and interferences. The optimum response was realized by biosensor constructed using 5 mg of dry cell weight per 100 mg of carbon paste in pH 5.5 preconcentration solution. Under the optimum experimental conditions, the developed microbial biosensor exhibited an excellent current response to Cu2+ over a linear range from 5.0 × 10-7 to 1.0 × 10-5 M (r2 = 0.9938) with a detection limit of 5.4 × 10-8 M (S/N = 3). The microbial biosensor had good sensitivity and reproducibility (R.S.D. 4.3%, n = 6). Finally, the applicability of the proposed microbial biosensor to voltammetric determination of Cu2+ in real sample was also demonstrated and validated with atomic absorption spectrophotometric (AAS) method. © 2008 Elsevier B.V. All rights reserved