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Abstract  

The uranium(VI) accumulation was studied in detail by using the biomass of mangrove endophytic fungus Fusarium sp.#ZZF51 from the South China Sea. The uranium(VI) biosorption process onto the tested fungus powders was optimized at pH 4.0, adsorption time 60 min, and uranium(VI) initial concentration 50 mg L−1 with 61.89% of removal efficiency. According to Fourier transform infrared spectra for the tested fungus before and after loaded with uranium(VI), the results showed that both of hydroxyl and carboxyl groups acted as the important roles in the adsorption process. In addition, the experimental data were analyzed by using parameter and kinetic models, and it was obtained that the Langmuir isotherm model and the pseudo-second-order kinetic model provided better correlation with the experimental data for adsorption of uranium(VI).

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Abstract  

Removal of uranium(VI) ions from acetate medium in aqueous solution was investigated using Lewatit TP260 (weakly acidic, macroporous-type ion exchange resin with chelating aminomethylphosphonic functional groups) in batch system. The parameters that affect the uranium(VI) sorption, such as contact time, solution pH, initial uranium(VI) concentration, adsorbent dose and temperature have been investigated. Results have been analyzed by Langmuir and Freundlich isotherm; the former was more suitable to describe the sorption process. The moving boundary particle diffusion model only fits the initial metal adsorption on the resin. The rate constant for the uranium sorption by Lewatit TP260 was 0.441 min−1 from the first order rate equation. The total sorption capacity was found to be 58.33 mg g−1 under optimum experimental conditions. Thermodynamic parameters (ΔH = 61.74 kJ/mol; ΔS = 215.3 J/mol K; ΔG = −2.856 kJ/mol) showed the adsorption of an endothermic process and spontaneous nature, respectively.

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Abstract  

Batch and dynamic extractions of uranium(VI) in 10−3–10−2M concentrations in 3–4M nitric acid medium have been investigated using a commercially available phosphinic acid resin (Tulsion CH-96). The extraction of uranium(VI) has been studied as a function of time, batch factor (V/m), concentrations of nitric acid and uranium(VI) ion. Dual extraction mechanism unique to phosphinic acid resin has been established for the extraction of uranium(VI). Distribution coefficient (K d) of uranium(VI) initially decreases with increasing concentration of nitric acid, reaches a minimum value at 1.3M, followed by increases in K d. A maximum K d value of ∼2000 ml/g was obtained at 5.0M nitric acid. Batch extraction data has been fitted into the linearized Langmuir adsorption isotherm. The performance of the resin under dynamic extraction conditions was assessed by following the breakthrough behavior of the system. Effect of flow rate, concentrations of nitric acid and uranium ion in the feed on the breakthrough behavior of the system was studied and the data was fitted using Thomas model.

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Abstract  

A continuous fixed-bed study was carried out by using zeolite as a low-cost adsorbent for the removal of uranium(VI) ions from aqueous solution under the effect of various process parameters such as the pH the bed depth, the flow rate, the presence of salt and the initial U(VI) ion concentration. The U(VI) ion uptake by zeolite increased with initial U(VI) ion concentration and bed height, but decreased as the flow rate increased. The adsorption capacity reached a maximum at pH of 6.0. A shorter breakthrough time was observed in the presence of salt. The experimental data obtained from the breakthrough curves were analyzed using the Thomas model. The BDST model was also applied to predict the service times for other flow rates and initial concentrations. The results showed that the Thomas model was suitable for the description of the whole breakthrough curve, while the data were in good agreement with the BDST model. The columns were regenerated by eluting the bound U(VI) ions with 0.1 mol L−1 NaHCO3 solution after the adsorption studies. After desorption and regeneration with deionized water, zeolite could be reused to adsorb uranium(VI) at a comparable capacity.

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