Nashrieh Shimi va Mohandesi Shimi Iran
Year:2013 | Volume:31 | Issue:3-4 (66)|Papers Count:13

Presence of toxic elements like cadmium, mercury and arsenic at ppb range in environmental resources may increase the risk to human health. Determination of these elements at such ranges needs a relative sensitive technique with enough low detection limit. Atomic absorption spectrometric methods provide simple and low cost techniques for such measurements. However, their detection limits in simple instrumentations lies in ppm ranges. At present work, sensitivity enhancement in determination of cadmium, mercury and arsenic using atom trapping and vapor generation techniques in atomic absorption spectrometry is investigated. In first step, an atom trapping device using a slotted quartz tube is fabricated. The device is then employed to analyzing those elements in aqueous solutions and a 2-3 enhancement is achieved. The detection limit of cadmium is improved from 20 ppb in simple FAAS to 5 ppb in atom trapping AAS. At second step, sensitivity enhancement for analyzing mercury and arsenic is investigated. A cold vapor generator is fabricated to analyzing mercury in aqueous solutions. The detection limit achieved by this method is 0.1 ppb which is 3 orders of magnitude better than flame one. The third step is determination of arsenic by hydride generation method, because cold vapor technique cannot be applied to this element. So, a hydride generator is fabricated with a slight modification of previously made cold vapor generator. A detection limit of 1 ppb is achieved by this method. In summary, such techniques provide simpler and cheaper analyzing methods for determination of volatile elements in aqueous samples. One may use specific digestion procedure for analyzing samples rather than aqueous one by such methods.

Phenol is a toxic and refractory water pollutant that cannot be completely degraded through common wastewater treatment methods. Methods such as active carbon adsorption, oxidation or biological digestion are not satisfying enough and only convert the pollutant from one phase to another, or may produce much more other toxic substances. The photo catalysis process is a new promising methodology among highly efficient methods for elimination of relatively recalcitrant organic compounds. Furthermore, application of nano materials as catalyst has successfully improved the efficiency of this method in this report; the aqueous oxidation of phenol over ZnO is investigated as a potential method for abatement of this pollutant. Concrete has been used as the immobilized surface and activation energy was provided with 8W UV-A lamps. Results of the SEM test also confirm an appropriate cover of ZnO on the concrete surface. The effects of operating parameters such as the initial phenol concentration, the light intensity, the dosage of ZnO particles, and pH were studied The photocatalytic system afforded the highest degradation efficiency at C0=50 mg/L, ZnO=80 g/m2, pH=11, light intensity=32 Wand over 90% of the initial phenol was degraded after 5 hours.

The basic purpose of this research was the investigation of cyanide adsorption on talc mineral surface from tailing dam water in Aghdareh-Takab gold processing plant. Then in this work, talc was used for adsorbing the cyanide from the tailing dam water. Solution pH, adsorption time, amount and size of talc and temperature are some importani parameters in the adsorption mechanism. Talc was used in two fraction (100-300) and (300-1000) microns in tests in two type (natural and impregnated) conditions. Optimum amounts talc for natural and impregnated types and maximum percent of cyanide adsorbed in (100-300)m are about 30 and 24(g/L) and 50.2% and 86.1% (300-1000)m are about 36 and 24(g/L) and 50.2% and 86.1% respectively. In any fractions optimum values of pH are 10.5 and 10 for natural and impregnated types respectively. Contact time in equilibrium conditions for each types of (100-300)m and (300-1000)m is 40 and 50 min respectively. In (100-300)m adsorption isotherm follow natural type from Frondlich and impregnated type of Longmuir models amount of cyanide adsorption on impregnated talc more than natural type.

Treatment of toxic nitrogen-containing compounds is one of the major applications of the Wet Air Oxidation (WAO) processes. The objective of this study is determining the efficiency of wet air oxidation process to remove ammonia from leachate in Esfahan Composing factory. Aqueous wastes containing organic pollutants can be efficiently treated by wet air oxidation, i.e. oxidation by molecular oxygen in the liquid phase, under high temperature (100-300oC) and pressure (up to IO bars). The results indicate that removal efficiency of NH3 at temperature 300oC and retention time 30 min 54.6 percent and the efficiency of nitrate produced 58.9%, after 30 min reaction at 300oC, 10 bars. In these conditions, the highest removal efficiency of ammonia and highest Amount of nitrate are produced. The average of NO3 production in this process is 32.5-58.9%. With further increasing temperature decomposition of organic material taken will be produced more ammonium. Also with increasing temperature and decreased retention time, ammonia oxidation to nitrate increased and nitrate are more produced. The WAO was an effective pre-treatment method for industrial wastewater and leachate with high amount of ammonia levels.

The supercritical carbon dioxide is applied in many separation processes as solvent. Due to this applicability of carbon dioxide, in this study, it is applied to oil refinery. In order to find the maximum efficiency, the experiment was conducted in the ranges of 150-210 bar of pressure, and 35-65oC of temperature. Based on this study, the changes in pressure show strong effect on the efficiency, and when it increases the efficiency increases, too. Despite of the pressure, when the temperature increases at a constant pressure, the density of supercritical carbon dioxide decreases. As a results, its solubility in decreases and the oil viscosity and mass transfer rate from oil increases. According to the results, the optimized operational condition to get the highest efficiency is investigated as 21 Obar of pressure and 45oC of temperature.

In this research, influence of several parameters for emulsion separation with high intensity ultrasonic standing wave field in a horizontal setup was investigated. Emulsion system considered for this study was crude oil in water. Experimental observations were indicated that ultrasound standing wave could break emulsions and separate them to their initial phases. But separation efficiency was depending on several operational parameters such as ultrasound intensity, sample position in ultrasound field and irradiation time period. It was also noticed that dispersed phase fraction and presence of surface active materials in sample emulsion had effects on emulsion creaming rate. Comparisons between experimental results were confirmed that the following as the optimum conditions for emulsion separation: 45% ultrasonic intensity, minimum distance from sound source (17.5 cm), maximum irradiation time (30 min), presence of 5% NaCl in initial emulsion formula and lowest oil concentration (5%). In this case, high intensity ultrasonic standing wave could completely separate oil in water emulsion.

The genus Xanthogalum is represented in the flora of Iran by just one species, namely Xanthogalum purpurascens. In this work, we report the antibacterial activity and the analysis of the leaf essential oil of X. purpurascens grown wild in Iran. The chemical composition of the essential oil from the leaves of X. purpurascens, collected from Mazandaran Province, were analysed by GC and GC/MS. Sixty-two components which representing 91.24% of the total composition were identified. 1,8-Cineole (17.59%, respectively), cis-muurol-5-en-4-a-ol (5.7%), neryl acetate (5.31%) and E-anethole (5.21%) were the main components in this oil. The antibacterial activities of the leaf oil of X. purpurascens were evaluated by disc diffusion method using Muller-Hinton Agar for bacteria with determination of inhibition zones and Minimal Inhibitory Concentration (MIC). The antibacterial activity showed that this oil had moderate Inhibitory against Klebsiella pneumonia. The leaf essential oil of X. purpurascens, was ineffective against Bacillus anthracis and Pseudomonas aeruginosa.

In this research, the essential oil of the aerial parts of Torilis leptophylla, collected from Ilam- Province and the essential oil of the aerial parts of Thecocarpus meifolius, collected from Shahre Kord were obtained by microwave and analysed by GC/MS. Spathulenol (15.74%), trans-a-bergamothene (9.37%) and germacrene D (8.94%) were the major constituents in the oil of T leptophylla. Spathulenol (30.8%), caryophyllene oxide (8.9%) and germacene D (6.0%) were the major in the oil of T meifolius. Antibacterial activity of both oils against gram-positive and gram-negative bacteria was investigated. Both oils showed weak activity against gram-positive bacteria.

Hemicellulose pre-extraction and recovering before pulping process is an approach for supplying the sugar feedstock used in production of fuels and chemicals. Wheat straw hot water pre-extraction for reaching to 10 % weight loss was carried out in the present study. Pre-extracted liquor from each stage was used as a media for subsequent extraction stage (three stages) in pre-extraction process. The results showed that soda-AQ pulping of pre-extracted straw is performed at less severe conditions i.e. shorter time and lower temperature as compared to non-pre-extracted straw. The pulping yield of pre-treated straw was higher than control pulp; however, the total pulp yield (based on oven dried weight of raw straw) was lower in the pre-extracted samples. Due to lack of hemicelluloses, pre-extracted pulps showed a weaker response to refining and the produced hand sheets had lower tear index and air resistant than hand sheets made of non-pre-extracted pulp, while no significant difference was noticed in burst and tensile indices of hand sheets produced from extracted and non-extracted pulp samples.

Limitation of natural resources especially cellulose reached by plant caused many researches has done for choosing on appropriate source of this material. Therefore, various methods have been evaluated for production cellulose. One of the significant methods of this biopolymer is using some different kind of bacteria which during recent decade has developed Bacterial cellulose has produced by saccharide carbohydrate source. In this article, at first bacterial cellulose nano fibers layer were produced from three different saccharide sources (glucose, sakaroz & lactose) in static medium culture. Moisture regain, FTlR, XRD and SEM were measurement methods which applied to investigate the structure of bacterial cellulose nano jibrille and finally compared with two cellulosic fibre (cotton & viscose). The results indicated that the width of bacterial cellulose fibril nano fibre was less than 100 nanometer. The crystallinity of produced layer from three sources was less than cotton (10-15) and was more than viscose (9%-13%). The crystal structure of all produced bacterial cellulose was type 1 but the amount of cellulose was different. The result of Moisture regain showed more amounts compared to Cotton (5%) and less than regenerated cellulose and viscose (3%).