Minerva Biotecnologica (11204826)27(1)pp. 43-49
Aim. The main goal of the present study was to study biotransformation of benzaldehyde to L-phenylacetyl carbinol (L-PAC) by free and immobilized cells of Saccharomyces cerevisiae. Yeast cells were immobilized both in calcium alginate and calcium alginate-PVAboric acid beads. Methods. Yeast cells were immobilized with calcium alginate and calcium alginate-PVA-boric acid beads. Free or immobilized cells were added to biotransformation medium containing benzaldehyde and acetaldehyde and incubated at 30 °C and 200 rpm in anaerobic conditions. Samples were taken every two hours. Concentrations of benzaldehyde, L-PAC, and benzyl alcohol were determined by gas chromatography. Effect of benzaldehyde concentration on L-PAC formation was investigated. Fed batch fermentation was performed using immobilized yeast cells in a 3 L bioreactor. Results. The optimum biotransformation of benzaldehyde to L-PAC was obtained at 2 g/L of benzaldehyde. Cells immobilized in calcium alginate-PVA beads produced approximately 2 g/L of L-PAC using 2 g/L of benzaldehyde in the second and third cycles. In fed batch fermentation, a concentration of nearly 3 g/L L-PAC was achieved. The highest obtained yields of L-PAC for free cells, immobilized cells in calcium alginate, immobilized cells in calcium alginate-PVA-boric acid, and fed batch fermentation were 0.55, 0.55, 1, and 0.64 g L-PAC per each gram of consumed benzaldehyde, respectively. Conclusion. This study showed that higher L-PAC titers can be obtained using immobilized yeast cells. Besides improved mechanical properties, cells immobilized in calcium alginate-PVA-boric acid beads exhibited higher production of L-PAC and lower amount of benzyl alcohol as compared to the cells immobilized in calcium alginate beads. © Copyright 2016 Edizioni Minerva Medica.
Zare, M.R.,
Kamali, M.,
Omidi, Z.,
Khorambagheri, M.,
Mortazavi, M.S.,
Ebrahimi, M.,
Akbarzadeh, G. Journal of Environmental Radioactivity (18791700)144pp. 134-139
Portable high-resolution gamma-ray spectrometry was carried out to determine the natural radioactivity levels in high volume surface water samples of the northern coast of Oman Sea, covering the coastal strip from Hormoz strait to Goatr seaport, for the first time. The water samples from 36 coastal and near shore locations were collected for analysis. Analyses on the samples collected were carried out to determine 226Ra, 232Th and 40K contents. The concentration of 226Ra, 232Th and 40K in surface water samples ranged between 2.19 and 2.82Bq/L, 1.66-2.17Bq/L and 132.6-148.87Bq/L, respectively. The activity profile of radionuclides shows low activity across the study area. The study also examined some radiation hazard indices. The external hazard index was found to be less than 1, indicating a low dose. The results of measurements will serve as background reference level for Oman Sea coastlines. © 2015 Elsevier Ltd.
Zare, M.R.,
Mostajabodaavati m., M.,
Kamali, M.,
Tari, M.,
Mosayebi, S.,
Mortazavi, M.S. Marine Pollution Bulletin (0025326X)92(1-2)pp. 201-211
This study aims to establish a managed sampling plan for rapid estimate of natural radio-nuclides diffusion in the northern coast of the Oman Sea. First, the natural radioactivity analysis in 36 high volume surface water samples was carried out using a portable high-resolution gamma-ray spectrometry. Second, the oceanic currents in the northern coast were investigated. Then, the third generation spectral SWAN model was utilized to simulate wave parameters. Direction of natural radioactivity propagation was coupled with the preferable wave vectors and oceanic currents direction that face to any marine pollution, these last two factors will contribute to increase or decrease of pollution in each grid. The results were indicated that the natural radioactivity concentration between the grids 8600 and 8604 is gathered in the grid 8600 and between the grids 8605 and 8608 is propagated toward middle part of Oman Sea. © 2014 Elsevier Ltd.
Pourimani, R.,
Abasnejad, K.,
Ghanbarzadeh, K.,
Zare, M.R.,
Kamali, M. Journal of Radioanalytical and Nuclear Chemistry (15882780)295(1)pp. 163-166
Accurate knowledge of the trace elemental concentrations in wheat and its products is of great importance from a nutritional point of view. In this study, six wheat samples were prepared from the agriculture research center of Arak named Sardari, Amir, MV-17, Batava, Karaj-2 and Alvand; they were analyzed by neutron activation method (NAA). In this method, Isfahan miniature reactor as a neutron source and relative NAA method has been used as the analysis type. In this design in order to record gamma spectrum the MCA system and high purity germanium detector were used. Finally, the concentration of the trace elements such as Br, K and Na value was determined for the Sardari, Amir, Alvand, MV-17, Batava, Karaj-2 wheat samples. The average concentration of trace elements in all wheat samples in the studied area are 2.41(0.8597-6.1175) mg kg-1 for Br, 13.42(8.7063-24.696) mg kg-1 for Na and 463.30(434.22-505. 45) mg kg-1 for K, respectively. These were compared with other reports results. This study has been conducted as the first time for this region. © 2012 Akadémiai Kiadó, Budapest, Hungary.
Marine Pollution Bulletin (0025326X)64(9)pp. 1956-1961
The natural radioactivity levels in sediment samples of the northern coast of Oman Sea, covering the coastal strip from Hormoz canyon to Goatr seaport, as the first time has been determined. The results of measurements will serve as background reference level for Oman Sea coastlines. Sediments from 36 coastal and near shore locations were collected for analysis. Analysis on the collected samples were carried out to determine 235U, 238U, 232Th, 40K and 137Cs using two high purity germanium detectors with 38.5% and 55% relative efficiencies. The concentration of 235U, 238U, 232Th, 40K and 137Cs in sediment samples ranged between 1.01 and 2.87Bq/kg, 11.83 and 22.68Bq/kg, 10.7 and 25.02Bq/kg, 222.89 and 535.07Bq/kg and 0.14 and 2.8Bq/kg, respectively. The radium equivalent activity was well below the defined limit of 370Bq/kg. The external hazard indices were found to be less than 1, indicating a low dose. © 2012 Elsevier Ltd.
Iranian Journal Of Chemistry And Chemical Engineering (10219986)31(4)pp. 21-28
A method for the controllable synthesis of silver nanoparticles based on a complexing agent method was developed. Citric acid was used as a complexing agent. The effect of pH (1.6 to 5.17) on the size and net height (as obtained from XRD analyses) of silver nanoparticles was investigated. The nanoparticles (10 to 40 nm) were characterized using XRD, TEM, SEM, EDX, UV-Vis spectroscopy and TG/DTG instrument. It was found that pH has a significant influence on both size and crystallinity of the nanoparticles. This is due to the effect of pH on the distribution of citrate ion species which in turn affects the size and crystallinity of the nanoparticles. Increasing the pH value enhances the percentage of [citrate3-] ion species which allows lower size and higher crystallinity of the nanoparticles. Thus, we were able to develop a method for the controllable synthesis of nanoparticles based on the pH.
Korean Journal of Chemical Engineering (19757220)28(2)pp. 370-377
Sn/Pt/Na-ZSM-5 was used as catalyst for the dehydrogenation of isobutane, and the effect of SiO2/Al2O3 ratio and the dispersion of Pt nanoparticles on the conversion and product selectivity were studied under atmospheric pressure at 848 K. The catalysts were characterized by various techniques such as H2 chemisorption, TEM, SEM, EDX, XRD, FT-IR, TG/DTG, elemental analysis by XRF and ICP techniques. Higher dispersion of Pt nanoparticles in the catalyst with SiO2/Al2O3 ratio of 40 resulted in higher selectivity for isobutene. © 2010 Korean Institute of Chemical Engineers, Seoul, Korea.
Applied Radiation and Isotopes (09698043)69(2)pp. 521-526
The concept of a virtual point detector (VPD) has been developed and validated in the past for Ge(Li) and HPGe detectors. In the present research, a new semi-empirical equation involving photon energy and source-virtual point detector distance for the efficiency of point sources by HPGe detectors is introduced , which is based on the VPD model. The calculated efficiencies for both coaxial and off-axis geometries by this equation are in good agreement with experimental data. The estimated uncertainties are less than 4%. © 2010.
Journal of Radioanalytical and Nuclear Chemistry (15882780)289(2)pp. 529-536
Adsorptive behavior of natural clinoptilolite was assessed for removal of thorium from aqueous solutions. Natural zeolite was characterized by X-ray diffraction and X-ray fluorescence. The zeolite sample composed mainly of clinoptilolite. Na-exchanged form of zeolite was prepared and its sorption capacity for removal of thorium from aqueous solutions was examined. The effects of relevant parameters, including initial concentration, contact time, solid to liquid ratio, temperature and initial pH on the removal efficiency were investigated in batch studies. The pH strongly influenced thorium adsorption capacity and maximal capacity was obtained at pH 4.0. Kinetics and isotherm of adsorption were also studied. The pseudo-first-order, pseudo-second-order, Elovich and intra-particle diffusion models were used to describe the kinetic data. The pseudo-second-order kinetic model provided excellent kinetic data fitting (R 2 > 0.999) with rate constant of 1.25, 1.37 and 1.44 g mmol-1 min-1 respectively for 25, 40 and 55 °C. The Langmuir and Freundlich models were applied to describe the equilibrium isotherms for thorium uptake and the Langmuir model agrees very well with experimental data. Thermodynamic parameters were determined and are discussed. © 2011 Akadémiai Kiadó, Budapest, Hungary.
Journal of Cluster Science (15728862)22(4)pp. 667-672
Silver nanoparticles were prepared using complexing agent method in which citric acid was used as the complexing agent. The effect of ammonium hydroxide and nitric acid addition on size, morphology, purity and surface area of nanoparticles were studied and compared. XRD, TEM, EDAX and BET were used for the characterization of synthesized nanoparticles. Addition of ammonium hydroxide led to smaller size of the silver nanoparticles. However, lower purity of nanoparticles was obtained when ammonium hydroxide was added to the mixture. However, the morphology of nanoparticles in both conditions is same. Also the experimental studies of nanoparticles surface areas show their tracking by size as we expected. These effects can be explained by the role of ammonium hydroxide and nitric acid on the direction of equilibrium reaction and affecting the solubility of silver citrate. © 2011 Springer Science+Business Media, LLC.
Tashauoei h.r., ,
Movahedian attar h., H.M.,
Amin, M.M.,
Kamali, M.,
Nikaeen m., ,
Dastjerdi, M.V. International Journal of Environmental Science and Technology (17351472)7(3)pp. 497-508
The sorption of cadmium and humic acids from aqueous solutions using surface-modified nanozeolite A has been investigated under various examination conditions. The morphology of untreated and treated nanozeolite was studied under scanning electron microscope and transmission electron microscope. Isotherms of cadmium adsorption onto surface-modified nanozeolite A were studied at different pH, solid to liquid ratio, adsorbate concentration and interaction time. Kinetic and equilibrium studies were conducted and the equilibrium data have been analyzed using Langmuir and Freundlich isotherm models. The study revealed that experimental results were in agreement with the Freundlich model. The Langmuir monolayer adsorption capacity was found to be 1666.67 g cadmium and 6.75 g humic acid per gram of modified nanozeolite A, which is higher than that of reported value for other zeolites. The sorption ability was enhanced by surface modification and reduction in size and enabled the zeolite to adsorb cadmium. The adsorption of cadmium and humic acid on nanozeolite was found to be the highest at pH 6 and 3, respectively. Results showed that solid to liquid ratio and pH are the most important factors for cadmium and humic acid removal, respectively. Effect of competitive ions was studied and results showed that there is no competition between cadmium and humic acid sorption and presence of these ions. © IRSEN CEERS IAU.
Tashauoei h.r., ,
Movahedian attar h., H.M.,
Kamali, M.,
Amin, M.M.,
Nikaeen m., International Journal Of Environmental Research (17356865)4(3)pp. 491-500
Chromium (VI) adsorption behavior and capacity by surface modified nanozeolite A has been investigated. Surface modification was performed and the morphology of modified and unmodified nanozeolite was studied using Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM). Adsorption isotherms were studied under different conditions (pH, adsorbent dose, adsorbate concentration and interaction time). The Langmuir monolayer adsorption capacity (qm) was found to be 14.16 mg Cr(VI) per gram at pH = 3.0 at room temperature. Chromate adsorption on surface modified nanozeolite A was found to be inversely proportional to the pH. Effect of competitive ions was studied and it was found that there is no significant competition between chromate adsorption and presence of competitive ions. Results revealed that Langmuir model is in good agreement with experimental re-sults. Results of examinations on a polluted natural sample showed that surface modified nanozeolite A could reduce chromium (VI) concentration to acceptable criteria. Based on results, surface modified nanozeolite A is an effective sorbent for removing chromate from aquatic solution and the adsorption ability is enhanced by surface modification.
Marine Pollution Bulletin (0025326X)58(5)pp. 658-662
The determination of activity concentrations of the radioactive elements 238U, 232Th, 40K and 137Cs was performed on grab samples taken from a polluted environment. The samples were sliced into strata from 5 cm depth, dried and ground to sieved through a 170 mesh size prior to the analysis. Activity concentration was quantified using gamma spectroscopy. The results showed that the concentrations of activity in the sediment samples are 177 ± 12.4, 117 ± 11.5, 1085 ± 101.6 and 131 ± 4.8 Bq kg-1 for 238U, 232Th, 40K and 137Cs, respectively. In general, the distribution of activity concentrations along the southern coast of the Caspian Sea area exceeded international limits. The hazard index of the samples was 0.19-0.88, with an average of 0.49. The mean values of radium equivalent activity and dose rate are 176 Bq kg-1 and 63 nGy h-1, respectively. © 2009 Elsevier Ltd. All rights reserved.
Powder Technology (1873328X)189(1)pp. 52-56
The zeolite NaA was synthesized from natural clinoptilolite as Si source and aluminum sulfate or sodium aluminate as Al source. The use of aluminum sulfate for the synthesis of zeolite A has not been reported in the literature. This study presents as the first time a synthesis approach in which the low cost and available source is used to prepare zeolite NaA. These nano particles of zeolite were prepared at different conditions in autoclave and a mixer was designed specifically for this purpose. The synthesized zeolites were characterized by instrumental analysis methods, such as X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscope (SEM), transmission electron microscope (TEM) and wet chemical analysis by atomic absorption spectroscopy (AAS). Cation exchange capacity (CEC) and loss on ignition (LOI) have been also measured on the prepared samples. The influences of different parameters such as reaction time, temperature, initial gel concentration, mechanical stirring and drying conditions on the improvement of the final products were experienced and the procedure for the efficient synthesis of zeolite NaA was optimized with available quality control tests. Solubility of clinoptilolite as the Si source in alkaline solutions was also investigated. © 2008 Elsevier B.V. All rights reserved.
Marine Pollution Bulletin (0025326X)56(4)pp. 751-757
A reconnaissance study has been made of the distribution of 238U, 232Th, 40K and 137Cs and geochemical features in soils and sediments samples at various locations in the northwestern coast of Persian Gulf. Activity concentration levels due to radionuclides were measured in 30 soil and sediment samples collected from this region. From the measured spectra, activity concentrations were determined for 40K (range from 146 to 500 Bq kg-1), 137Cs (from 5 to 20 Bq kg-1), 238U (from 21 to 65 Bq kg-1) and 232Th (from 15 to 45 Bq kg-1) with lowest limit detection (LLD) of 68, 3.2, 4.3 and 4.3 Bq kg-1, respectively. The dose rate from ambient air at the soil ranges was between 19 and 58 nGy h-1 with an average of 37.41 ± 9.66 nGy h-1. © 2007 Elsevier Ltd. All rights reserved.
Journal of Radioanalytical and Nuclear Chemistry (15882780)270(2)pp. 319-324
A reconnaissance study has been made on the distribution of 238U, 232Th, 40K, 137Cs and geochemical features in soil and sediment samples at various locations in the coast of Persian Gulf. Activity concentration levels due to radionuclides were measured in 50 samples of soils and sediments collected from the coast of Hormozgan. From the measured spectra, activity concentrations were determined for 40K (range from 140 to 1172 Bq·kg-1), 137Cs (from 0 to 15 Bq·kg-1), 238U (from 29 to 385 Bq·kg-1) and 2321Th (from 9 to 156 Bq·kg-1) with the lowest limit of detection (LLD) of 68, 3.2, 4.3 and 4.3 Bq·kg-1, respectively. The dose rate from ambient air at the soil ranges was between 23 to 177 nGy·h-1 with an average of 60±7.86 nGy·h-1. © 2006 Akadémiai Kiadó.
Iranian Journal of Science and Technology, Transaction A: Science (10286276)30(3)pp. 259-269
A reconnaissance study has been made on the distribution of 238U, 232Th, 40K, 137Cs and geochemical features in soil and sediment samples at various locations on the coast of Bushehr in the Persian Gulf. In this study a gamma-ray spectrometer based on a High Purity Germanium detector and a PC based MCA and X-ray fluorescence (XRF) method were used. Estimation of the measured radionuclide content have been made for the absorbed dose rate of gamma radiation. The Activity concentration (A), the equivalent radium (Req), and the external hazard index (Hex) which resulted from the natural radionuclides in soil and sediment are also calculated. The base-line data of radionuclides and heavy metals in view of the commissioning of nuclear and non-nuclear industries for the coast of Bushehr, which does not yet exist, was obtained. Activity concentration levels due to radionuclides were measured in 50 soil and sediment samples collected from this region. The measurement was performed with respect to their gamma radioactivity for a counting time of 24 hour intervals. From the accumulated spectra, activity concentration were determined for 40K (range from 108 to 520 Bq Kg-1), 137Cs (from 6 to 40 Bq Kg-1), 238U (from 12 to 75 Bq Kg1) and 232Th (from 8 to 33 Bq Kg-1) with the lowest limit detection (LLD) of, respectively, 68, 3.2, 4.3 and 4.3 Bq Kg-1. The dose rate from ambient air at the soil ranges was between 14 to 44 nGy h-1 with an average of 30.56 ± 7.86 nGy h -1. © Shiraz University.
Journal of Radioanalytical and Nuclear Chemistry (15882780)268(3)pp. 539-544
A nonlinear function was applied in combination with the method of mixing activity calibration for fitting the experimental peak efficiency of HPGe spectrometers in the 50-2614 keV energy range. The preparation of Marinelli beaker standards of mixed gamma- and RG-Set at secular equilibrium with its daughter radionucliedes was studied. Self-absorption was measured for the activity calculation of the gamma-ray lines for daughters of 238U series, 232Th series, as well as 137Cs and 40K in soil samples. Self-absorption in the sample depends on a number of factors including sample composition, density, sample size and gamma-ray energy. Seven Marinelli beaker standards were prepared in different degrees of compaction with bulk density (ρ) of 1.000 to 1.600 g·cm-3. The detection efficiency versus density was obtained and the equation of self-absorption correction factors was calculated for soil samples. © 2006 Akadémiai Kiadó.
International Journal of Environment and Pollution (09574352)19(6)pp. 557-566
With the aim of the economic upgrading of natural resources, this investigation examined the hydrothermal synthesis of zeolite from perlite, and the ability of the synthetic zeolite to adsorb and retain cyanide. The hydrothermal treatment of perlite with aqueous sodium hydroxide results in the formation of Na-Pc zeolite. The cation-exchange capacity of zeolite for zinc, copper and silver was respectively 2.26, 1.86 and 2.44 meq g -1. The exchange was incomplete, but equilibrium was rapidly attained. Cyanide adsorption isotherms, constructed at three different temperatures, showed that the zeolite was very selective for cyanide. The solubility products of the cyanide precipitate and the exchange capacity of zeolite for individual cations governed the adsorption capacity of the zeolite. The method also remains selective in the presence of some other anions. Kinetic data for cyanide desorption in water and sodium chloride solution indicated that zeolite retains most of the adsorbed cyanide.
