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Khani M.H.,Nuclear Science and Technology Research Institute, Iran
Environmental Science and Pollution Research | Year: 2011

Introduction: Kinetic, thermodynamic, and equilibrium isotherms of the biosorption of uranium ions onto Padina sp., a brown algae biomass, in a batch system have been studied. Discussion: The kinetic data were found to follow the pseudo-second-order model. Intraparticle diffusion is not the sole rate-controlling factor. The equilibrium experimental results were analyzed in terms of Langmuir isotherm depending with temperature. Equilibrium data fitted very well to the Langmuir model. The maximum uptakes estimated by using the Langmuir model were 434.8, 416.7, 400.0, and 370.4 mg/g at 10°C, 20°C, 30°C, and 40°C, respectively. Gibbs free energy was spontaneous for all interactions, and the adsorption process exhibited exothermic enthalpy values. Padina sp. algae were shown to be a favorable biosorbent for uranium removal from aqueous solutions. © 2011 Springer-Verlag.

Khani M.H.,Nuclear Science and Technology Research Institute, Iran
Environmental Science and Pollution Research | Year: 2011

Introduction: The application of response surface methodology is presented for optimizing the removal of U ions from aqueous solutions using Padina sp., a brown marine algal biomass. Methods: Box-Wilson central composite design was employed to assess individual and interactive effects of the four main parameters (pH and initial uranium concentration in solutions, contact time and temperature) on uranium uptake. Results and discussion: Response surface analysis showed that the data were adequately fitted to second-order polynomial model. Analysis of variance showed a high coefficient of determination value (R2 = 0.9746) and satisfactory second-order regression model was derived. Conclusion: The optimum pH and initial uranium concentration in solutions, contact time and temperature were found to be 4.07, 778.48 mg/l, 74.31 min, and 37.47°C, respectively. Maximized uranium uptake was predicted and experimentally validated. The equilibrium data for biosorption of U onto the Padina sp. were well represented by the Langmuir isotherm, giving maximum monolayer adsorption capacity as high as 376.73 mg/g. © 2010 Springer-Verlag.

Biosorption of lanthanum (III) and cerium (III) from aqueous solution by tangerine (Citrus reticulate) peel has been investigated in a batch system as a function of pH, biosorbent dosage, contact time, and temperature. The equilibrium pH was found to severely affect the biosorption performance; pH 5.0 was found to be an optimum pH for favorable biosorption of La (III) and Ce (III). The biosorption of lanthanum and cerium was investigated by the Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherm models. Maximum biosorption uptakes, according to the Langmuir model, were obtained as 154.86 and 162.79 (mg/g) for La(III) and Ce(III), respectively. The biosorption kinetic was tested with pseudo-first order and pseudo-second order models. The results showed that the kinetics of the biosorption process were described by the pseudo-second order model very well. Thermodynamic parameters including the change of Gibbs free energy (ΔG°), enthalpy change (ΔH°) and entropy change (ΔS°) for both sorption systems were determined at four different temperatures. The results showed that the biosorption of La(III) and Ce(III) on tangerine (C. reticulate) peel is a spontaneous and endothermic process. FTIR analysis demonstrated that carboxyl and hydroxyl groups were involved in the biosorption of the metal ions.

Doroudi A.,Nuclear Science and Technology Research Institute, Iran
International Journal of Mass Spectrometry | Year: 2010

In this paper the homotopy perturbation method is used for calculation of axial secular frequencies of a nonlinear ion trap with only hexapole superposition. The motion of the ion in a rapidly oscillating field is transformed to the motion in an effective potential. The equation of ion motion in the effective potential is the equation of an anharmonic oscillator with quadratic nonlinearity. The homotopy perturbation method is used for solving the resulted nonlinear equation and obtaining the expression for ion secular frequency as a function of nonlinear field parameter. The calculated secular frequencies are compared with the results of L.-P. method and the exact results. © 2010 Elsevier B.V.

Hosseinkhani H.,Nuclear Science and Technology Research Institute, Iran | Modarres M.,University of Tehran
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2012

The leading order (LO) and the next-to-leading order (NLO) unintegrated parton distribution functions (UPDF) are calculated by using the latest version of integrated parton distribution functions (PDF) of Martin et al. (MSTW2008) as the inputs. Similar to our previous works, rather than the Ciafaloni-Catani-Fiorani-Marchesini (CCFM) evolution equations, the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) collinear approximation is used to consider the dependence of parton distributions on the second scale, kt2, the partons transverse momenta, beside the first scale, μ 2, which is included in the last step of DGLAP evolution equation (Kimber et al. procedure). The three-dimensional UPDF are presented in terms of different [x, μ 2]-planes and in the range of CERN LHC energies and the parametrization procedure for the various values of kt2. It is shown that the two-scale UPDF behave similar to their corresponding PDF at large kt2≃106GeV2. In both LO and NLO levels at each kt2 a peak is observed around μ2=kt2 especially at x≃10 -4 (x≤10 -4) for the gluons (quarks). In contrast to the complication which exists in the parameterized PDF i.e. the negative gluon distribution at small x and μ 2, the UPDF are always positive except at large x (≃1) which is mainly due to the angular ordering which makes numerical instability in this region (the values of UPDF are very small). We hope present results could help a better understanding of the LHC data at CERN. © 2012 Elsevier B.V.

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