Adsorption of ⁶⁰Co²⁺ on hydrous manganese oxide powder from aqueous solution

Abstract

Adsorption / Hydrous manganese oxide / 60 Co 2+ / Freundlich adsorption / Radioactive waste / Desorption Summary. Hydrous manganese oxide (HMO) was synthesized and its ability to sorb 60 Co 2+ from aqueous solution was studied under static conditions as a function of contact time, cobalt concentration (10 −2 -10 −7 M), temperature (303-333 K) and pH of adsorptive solution (2.2-11.4). X-ray diffraction was used in characterization of synthesized HMO. Low concentration of 60 Co 2+ solution, high pH and high temperature were the most favorable conditions for the adsorption process. The results show that the removal process is complete in 40 minutes, obeys a first order rate law and can be described using the Freundlich adsorption model. The standard enthalpy of the system was ∆H 0 = 12.5 ± 0.2 kJ mol −1 and cobalt desorption indicates that the uptake process proceeds via cation exchange. The removal of cobalt ions by HMO appears to be endothermic and irreversible. The values of calculated ∆G 0 and ∆S 0 were − 17.0 ± 3.0 kJ mol −1 and (9.8 ± 0.2) × 10 −2 kJ K −1 mol −1 respectively, this indicates spontaneity of the process and the degree of freedom of ions is increased by adsorption.

Removal of Chromium Hexavalent Ions From Aqueous Solution by Retention Onto Iron Phosphate

“…The value obtained for 1/n was attributed to the heterogeneous nature of the adsorbent surface with an exponential distribution of the retention sites. 32 As can be observed in Fig. 6, a straight line was obtained with a high correlation factor (0.9860), indicating that the retention data fit well to the Freundlich isotherm model.…”

“…On the other hand, data were also evaluated with the Dubinin-Radushkevich (D-R) adsorption isotherm in their linearized form 32 : (5) where ß is a constant and ε is the Polanyi retention potential that can be calculated with the following equation: (6) where r is the gases constant (8.314 x 10 -3 kJ/mol K) and T is the absolute temperature in Kelvin. This isotherm postulates a fixed volume or "adsorption space" close to the adsorbent surface where adsorption takes place.…”

Chromium (VI) adsorption on boehmite

“…The slope of the plot is a max = (5.432 ± 0.01) × 10 −6 mol g −1 and intercept is K = (1.81 ± 0.1) × 10 4 dm 3 mol −1 , with a higher correlation coefficient (R 2 = 0.9930). On the other hand, data were also tested with D-R equation in the linearized form [25,26]:…”

“…Enthalpy change was calculated from the slope of straight line plot between log K d and 1/T in Fig. 10, derived from application of the van't Hoff equation in linearized form [25]:…”

Influence of Textural Properties and Surface Fractal Dimensions on the Cobalt Adsorption Behavior of Rice Hull Ash Prepared via Solid Combustion

“…6H 2 O) in water (pH = 6.32), and the mixtures were stirred constantly for 2 h as a pre-established equilibrium time. 28 Phases were then separated by centrifugation for 5 min at 6000 rpm. Then, a 1-mL aliquot of the liquid phase was analyzed by ultraviolet-visible spectroscopy (UV-Vis) using a PerkinElmer Spectrometer Lambda 10 at λ = 265 nm.…”