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In the present study, the removal of Cr(VI) from aqueous solution by aStrychnos nux-vomicashell was examined in a batch study. The main process parameters such as adsorbent dose, pH, initial concentration, temperature, agitation speed and contact time were studied. The result shows that the maximum removal of Cr(VI) was observed at pH 2. The progressive changes on surface texture and the confirmation of chromium binding on adsorbent surface at different stages were obtained by the scanning electron microscopy, energy-dispersive X-ray spectroscopy and Fourier transform infrared spectrometer analysis. The equilibrium data from the biosorption study was evaluated by the use of two parameter isotherm models. Langmuir isotherm model seems to fit better with the equilibrium data. Kinetic studies were performed using pseudo-first-order, pseudo-second-order and intraparticle diffusion models. The biosorption data were found to best fitted for pseudo-second-order kinetic model. The calculated thermodynamic parameters such as ΔG°, ΔH° and ΔS° showed that the adsorption of Cr(VI) ions onto adsorbents was spontaneous, endothermic and increased randomness in nature. The results indicate that STFS can be an effective adsorbent for the removal of Cr(VI) from aqueous solutions. [ABSTRACT FROM PUBLISHER]

In this study, batch removal of hexavalent chromium from aqueous solutions by powdered Colocasia esculenta leaves was investigated. Batch experiments were conducted to study the effects of adsorption of Cr(VI) at different pH values, initial concentrations, agitation speeds, temperatures, and contact times. The biosorbent was characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Fourier transform infrared spectrometer analysis. The biosorptive capacity of the adsorbent was dependent on the pH of the chromium solution in which maximum removal was observed at pH 2. The adsorption equilibrium data were evaluated for various adsorption isotherm models, kinetic models, and thermodynamics. The equilibrium data fitted well with Freundlich and Halsey models. The adsorption capacity calculated was 47.62 mg/g at pH 2. The adsorption kinetic data were best described by pseudosecond- order kinetic model. Thus, Colocasia esculenta leaves can be considered as one of the efficient and cheap biosorbents for hexavalent chromium removal from aqueous solutions. [ABSTRACT FROM AUTHOR]