Heidary S.,University of Tehran |
Setayeshi S.,University of Tehran |
Ghannadi-Maragheh M.,NSTRI |
Radiation Measurements | Year: 2011
A new radon calibration chamber has been designed, constructed and tested to set various desired environmental parameters. The chamber is cubic with two trapezoid sides with a total volume size of 0.498 m3. The three parameters, temperature, humidity and flow are controlled in the range of 20-45 °C (±2 °C), 10-70% (±2.5%) and 0.2-10 m3/min (±0.1 m3/min) respectively. The chamber is equipped with a controllable speed centrifugal fan to achieve a desirably uniform radon flow rate. Many parts of this system are controlled and monitored with a PLC (Programmable Logic Control) and HMI (Human Monitoring Interface) software (Citect Scada). Finally a radon detector (Alpha-Guard) registers the activity parameter. © 2011 Elsevier Ltd. All rights reserved.
Development, Characterization and Ion Exchange Thermodynamics for a New Crystalline Composite Cation Exchange Material: Application for the Removal of Pb 2+ Ion from a Standard Sample (Rompin Hematite)
AL-Othman Z.A.,King Saud University |
Naushad M.,King Saud University |
Journal of Inorganic and Organometallic Polymers and Materials | Year: 2011
A new crystalline organic-inorganic composite cation exchanger polyaniline Sn(IV) molybdate was developed by mixing polyaniline into the inorganic precipitate of Sn(IV) molybdate. This material was characterized using Fourier transform infrared spectroscopy (FTIR), simultaneous thermogravimetry-differential thermogravimetry (TGA-DTA), X-ray, scanning electron microscopy (SEM) and elemental analysis studies. Ion-exchange capacity, effect of calcinations (100-500 °C) on ion exchange capacity, pH-titrations, chemical stability, elution and distribution behavior were also carried on this material. On the basis of distribution studies, the material was found to be highly selective for Pb 2+ ion and its selectivity was tested by achieving some important binary and ternary separations. In order to demonstrate the practical utility of the material, quantitative separations of Pb 2+ from a standard reference material (Rompin Hematite) of lead have been achieved. Thermodynamic parameters viz- entropy change (ΔS), enthalpy change (ΔH) and Gibb's free energy change (ΔG) were also calculated. © 2011 Springer Science+Business Media, LLC.
Arabieh M.,NSTRI |
Platas-Iglesias C.,University of La Coruna
Computational and Theoretical Chemistry | Year: 2016
The most feasible complexes formed between dipicolinic acid and hydrated Fe2+ cation (namely, [FeL(H2O)3] and [FeL2]) have been modeled using density functional theory. A comparison among several computational levels of theory and available X-ray data showed that the B3LYP/6-311G(d) computational level provides accurate geometrical parameters for geometry optimization of complexes. The energetics and thermochemistry of complexation reactions in the gas phase and solvated medium (PCM) were evaluated at the B3LYP/6-311G(d) and B3LYP/6-311++G(2df,pd)//B3LYP/6-311G(d) levels of theory. The calculated thermochemistry data exhibited high complexation energies for both complexes and decreasing in the exothermicity of complexation reactions when PCM model was included in the calculations. The calculated free energy changes of complexation reactions pointed to spontaneous procedures. Detailed analysis of energy levels and major composition of selected frontier orbitals were performed and the results suggested the higher stability for the [FeL(H2O)3] system than for [FeL2]. Based on QTAIM, several bond-indexes such as electron density at the bond critical points, the Laplacian of the electron density, ellipticity and the total energy density were utilized to analyze chemical bonding in these complexes. Natural bond orbital (NBO) analysis was carried out to provide more precise insight on the interactions and nature of the bonds established between the ligand and the metal ion. © 2016 Elsevier B.V.
Shokati Poursani A.,Islamic Azad University at Tehran |
Nilchi A.,NSTRI |
Hassani A.H.,Islamic Azad University at Tehran |
Shariat M.,Islamic Azad University at Tehran |
Nouri J.,Islamic Azad University at Tehran
International Journal of Environmental Science and Technology | Year: 2015
Nano-γ-Al2O3 adsorbent was synthesized by the novel sol–gel method. The adsorbent was characterized by transmission electron microscope, Fourier transform infrared and X-ray powder diffraction. The effects of several variables such as, adsorbent weight, pH and contact time on adsorption of chromium (Cr6+), nickel (Ni2+), cadmium (Cd2+) and lead (Pb2+) ions were studied in batch experiments. The results showed that the synthesized nano-γ-Al2O3 had a good capacity to adsorb Cr and Pb. The kinetic data were described with pseudo-first- and pseudo-second-order models. Three isotherm models, namely Freundlich, Langmuir and Tempkin, were used for analysis of equilibrium data, and results showed that Langmuir and Freundlich models were suitable for describing the equilibrium data of Cr6+, Cd2+, Ni2+ and Pb2+. Using Langmuir isotherm, the maximum sorption capacities of Cr6+, Pb2+, Cd2+ and Ni2+ were estimated to be 13.3, 6, 1.1 and 0.33 (mg/g) at 25 °C, respectively. The sorption capacity did not change remarkably after reuse of sorbent for sorption–desorption cycle. The selectivity order of Cr6+, Pb2+, Cd2+ and Ni2+ sorption onto the adsorbent was Cr6+ > Pb2+ > Cd2+ > Ni2+. © 2015, Islamic Azad University (IAU).
Salahinejad M.,Environmental Laboratory |
Journal of Nanoparticle Research | Year: 2013
Artificial neural network (ANN) and multiple linear regression (MLR) approaches were successfully applied to construct quantitative structure-activity relationship models of the dispersibility of single-walled carbon nanotubes (SWNTs) in different organic solvents. A subset of the calculated descriptors selected by enhanced replacement method (ERM) was used in the QSPR models development. The predictive abilities of ERM-MLR and ERM-ANN models were determined using a test set of six organic solvents affording predictive correlation coefficients of 0.924 and 0.963, respectively, showing good predictive power of the models obtained. The final models satisfied a set of rigorous validation criteria and performed well in predicting of the external test set. The results obtained in this study, confirm the importance of steric and electrostatic interactions, molecular flexibility, polarizability and hydrogen bonding ability of organic solvents in SWNTs dispersibility. This information could be useful for identification of some key molecular features of solvent molecules and to find the proper solvent for SWNTs dispersion. © Springer Science+Business Media 2013.