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Showing 8 results for Silica

A Naghizadeh, Ah Mahvi, H Jabbari, A Dadpour4, M Karimi,
Volume 1, Issue 1 (10-2008)
Abstract

Background and Objectives: Silica is an inorganic material that found in the nature in various forms. The hazards of crystal of silica or α-quartz (free silica) is greater than other forms. Exposure to dust that contains free silica result to pulmonary injury and result to silicosis and death finally. The present research was conducted in order to evaluate the level of workers exposure to free silica in air of Khaf Iron stone quarries.Materials and methods: The exposure level to total and respiratory dust measured based on personal and environmental sampling methods and concentration of dust determined based on gravimetric method. For determination of amounts of free silica, dust samples analyses based on X-ray diffraction (XRD) method, and results compared with standard levels.Results: The maximum amount of total dust and free silica measured in stone breaking station (800±155mg/m3 and 26.11±6.7 mg/m3) and minimum of them measured in official and safeguarding station (8.28±2.2 mg/m3 and 0.012±0.0019 mg/m3). The maximum amount of respiratory dust and free silica measured in red mound digging number 1 (66.14±13.45 mg/m3 and 1.48±0.39 mg/m3) and minimum of them measured in air hammer machine station (5.26±2.62 mg/m3 and 0.01±0.005 mg/m3).Conclusion: Amount of total dust only in official and safeguarding station was lower than standard levels of Iran. Amount of respiratory dust in all stations was greater than Iran standard levels. Furthermore the level of respiratory free silica only in airy hammer machine station was lower than standard level of Iran. Regarding to this amounts it is so essential to that with applying different methods generation and emission of dust protected.

 


Hossein Amjadsoroudi, Farshid Ghormani Shahna, Abdorahman Bahrami, Javad Fardmal,
Volume 6, Issue 1 (5-2013)
Abstract

Background and Objectives: Cyclone is one of the most utilized dust collectors for airborne particles control. It separates particles from airflow by centrifugal force. However, it is not effective in collecting very fine particles smaller than 10 μm in diameter. The aim of this study was to assess the performance of charging particles on cyclone efficiency in collecting particles smaller than 1 μm.
 Materials and Methods: To achieve the above aim, a pilot air conditioning system equipped with conventional cyclone of Lapple model was designed and installed. A high voltage (18 KV) DC power supply was used for charging silica particle in corona charger. Isokinetic probe was used for particles sampling at upstream and downstream of cyclone under different study conditions and measurement was carried out using Grimm 1.08 dust counter.
Results: Charging fine airborne silica particles caused a significant increase in collection efficiency. There is a direct relationship between collection efficiency and charging voltage, so that the total particles collection efficiency was increased from 2.7 to about 72% with respect of increasing charging voltage from zero to 18 Kv. However, inlet air velocity has a negative effect on the collection efficiency of particles charged.
Conclusion: Applying electrocyclone in collecting fine particles smaller than 1 µm is more efficient compared with that of conventional cyclones.


A.r Rahmani, F Nazemi, F Barjasteh Askari, H Almasi, N Shabanloo, A Shabanloo,
Volume 9, Issue 1 (6-2016)
Abstract

Background and Objectives: Phenol is a toxic and persistent substance in the environment. The aim of this study was to evaluate the performance of silica aerogel synthesized using sodium silicate in the adsorption of phenol from aqueous solutions.

Material and Method: Silica aerogel was prepared by Sol-Gel process. The influence of effective variables such contact time, initial pH of the solution, adsorbent dose, and initial phenol concentration on the adsorption efficiency was investigated. The characterization of prepared silica aerogel and confirmation of phenol adsorption was determined through SEM, XRD analysis and NMR, FTIR spectra respectively. The adsorption data was evaluated via Langmuir and Freundlich isotherms and pseudo-first and pseudo-second-order kinetics.

Results: This research found that the phenol adsorption efficiency increased by increasing pH from 3 to 11, so that after 60 min, the absorption efficiency at the 100 mg/L initial phenol concentration and 0.5 g adsorbent obtained 84 and 96.4 % at pH 3 and 11, respectively. The SEM image and XRD patternof synthesized silica aerogel confirmed the creation of porous and amorphous structure. After the phenol absorption, the NMR and FTIR spectra of silica aerogel, confirmed the creation of new bands because of phenol molecule at the adsorbent structure. The absorption of phenol was compatible with Freundlich isotherm and pseudo-second-order kinetic. The maximum absorption capacity (qm) obtained was 47.39 mg/g.

Conclusion: Silica aerogel as an adsorbent, due to special characteristics in the structure and usage, can be a promising treatment process for adsorption of toxic and persistent substances.


N Farrar, Sr Golestaneh, S Rasoulian,
Volume 11, Issue 3 (12-2018)
Abstract

Background and Objective: The sewer system is one of the important and suitable areas for the growth and reproduction of American Cockroach Periplaneta americana (L.) in Bushehr. This project was implemented for considering the high cost of spraying and environmental pollution.
Materials and Methods: In this study some commonly insecticides were tested in different doses to evaluate the effectiveness on cockroaches in sewer system. Three treatments including the combination of the insecticide with class B diatomaceous earth, solid silica gel and boric acid were evaluated in manholes of sewer system. In this regard, the Bushehr city was divided into ten clusters based on its sewer system and then, ten manholes were selected randomly from each area to survey and conduct field experiments. A random-cluster sampling method was used to generalize the results of the whole system. The mortality rate was corrected on control mortality with the Henderson-Tilton formula.
Results: Experimental insecticides spraying controlled up to 100 percent of cockroaches in the laboratory. However, using insecticide alone reduced the mortality rate in manholes over time. The results of statistical tests showed that the most effective method in destroying cockroach was the usage of the compounds of insecticide, mineral and non-chemical substances which caused mortality rate more than 90% up to 12 months.
Conclusion: As little as 50 g/manhole of a dust consisting of 5% silica gel, 35% boric acid, 60% diatomaceous earth with a commercial insecticide such as Deltamethrin sprayer provided more than 98% control for 12 months.
 

Mansoureh Hamidi, Parvin Nassiri, Homayoon Ahmad Panahi, Lobat Taghavi, Saeed Bazgir,
Volume 13, Issue 3 (11-2020)
Abstract

Background and Objective: Noise pollution is one of the serious environmental issue. Sound control technologies based on sound absorption and sound insulation are considered as the two widely used methods. Therefore, the aim of this study was to modify silica aerogel nanocomposites to improve its acoustic properties.
Materials and Methods:  This applied experimental research involved in examining eight various types of nanocomposites to evaluate their performance of acoustic properties. In this study, nanocomposites were synthesized by sol-gel method. For this purpose, TEOS and ethanol were added to SiO2 which subsequently stirred and diluted with ethanol as a precursor of silica sol. A solution of 5.5 M ammonium hydroxide is added drop-wise to the silica sol and then was stirred. The activated silica sol was quickly poured into the mold in which the samples were placed and finally placed in an oven at 150 °C for 3 hours. The acoustic properties of the samples were measured by the impedance tube and the reduction sound pressure level using a sound level meter. Each sample morphology was characterized by scanning electron microscopy.
Results: The sound absorption properties of as prepared nanocomposite relatively increased at high frequencies. The results indicated > 0.6 sound absorption coefficient by the modified nanocopmosites at higher frequencies. The sound absorption coefficient and transmission loss of D1 nanocomposite were higher at medium and low frequencies as compared to other nanocomposites. 4.6 and 9.73 dB average reduction of sound pressure level were achieved by either with or without nanocomposite enclosure, respectively, at a distance of 1 meter.   
Conclusion: The results of the current study showed that the simultaneous addition of organic and mineral materials to silica aerogels (especially with the highest amounts of nanoclay) improves its acoustic properties, especially at medium and low frequencies. Among the samples, D1 nanocomposite shows better acoustic properties at medium and low frequencies. The sound absorption coefficient of D1 nanocomposite at frequencies of 315, 400, 500, 1000, 1250, 2000 Hz were obtained as 0.27, 0.38, 0.51, 0.78, 0.83 and 0.84, respectively. The findings also indicated 9.37 dB reduction of sound pressure level using D1 nanocomposite.

Arash Babaei, Maryam Bahrami, Masoomeh Maleki, Hadis Tavafi,
Volume 13, Issue 4 (2-2021)
Abstract

Background and Objective: Bioremediation and one of its main branches, namely phytoremediation, is one of the most important and basic processes for eliminating pollutants from the environment. Due to the large number of silica factories in Azandarian area of ​​Malayer city and high soil silica pollution in this area, this study was conducted to compare the bioremediation effect of Fusarium oxysporum and Portulace olerace.L phytoremediation on silica uptake.
Materials and Methods: For this purpose, portulaca oleracea was cultivated in greenhouse conditions and different concentrations of silica and under the treatment of fungi in a completely random statistical design. For this purpose, portulaca oleracea cultivation was carried out under greenhouse conditions, fungal treatment and in different concentrations of silica in a completely randomized manner.
Results: The results showed that the fungus grew easily at high speed at 95% concentration of silica and was able to absorb 84.50% of the silica in the soil and the plant was able to absorb 80% of silica, the highest absorption rate of 69.71% and the highest rate of silica uptake in plant and fungus coexistence is 80% silica and 69.90%. The results showed that the fungus grew easily in the presence of silica with 95% concentration and could absorb 84.50% of silica in the soil. In the presence of 80% silica, the plant demonstrated the highest adsorption rate of 61.71%. The highest rate of silica uptake (69.90%) was reached at the 80% initial concentration of silica under the coexistence activities of plant and fungi.
Conclusion: In conclusion, silica exhibited a positive and significant effect on the physiological traits of Portulaca oleracea and also increased the amount of phenol, flavonoids, and anthocyanins. The coexistence of fungi and plants also increased the mentioned physiological traits in Portulaca oleracea. Also, the coexistence of plants and fungi showed a positive effect on silica adsorption, which can be effective in reducing silica contamination in the region.

Mahsa Jahangiri-Rad, Mohammad Rafiee,
Volume 14, Issue 3 (12-2021)
Abstract

Background and Objective: Corrosion and precipitation are important indicators of water quality assessment. The aim of this study was to analyze water stability water in Semnan distribution networks.
Materials and Methods: To achieve the purpose, samples were taken from 5 points (3 points of storage tanks and 2 distribution network points) and analyzed for physical-chemical analysis. The concentration of common anions and cations was determined by ion chromatography (IC). The sediment formed in the water distribution network was also investigated for studying its structure and main elements by using X-ray fluorescence spectroscopy (XRF) and induced coupling plasma spectroscopy (ICP). The corrosion and scaling indices, including the Ryznar stability index (RSI), Langelier index (LI), and calcium carbonate precipitation potential (CCPP) were also studied.
Results: According to the obtained results, the quality (physically-chemically) of most of the taken samples lies within the permissible limits of Iran's national standard (1053). However, in terms of total harness all sampling point showed values beyond WHO guidelines for drinking water. Magnesium and sulfate concentrations were also exceeded in one of the reservoirs. The results also showed the main sediment structures were calcium carbonate (calcite) and silica oxide. Moreover, According to the results, the average values of LSI and CCPP represented the scaling due to carbonate calcium nature of water. Water stability analysis indicated major roles of calcium and magnesium bicarbonate formation as temporary hardness and minor roles of magnesium sulfate and chloride as permanent hardness.
Conclusion: According to the results, to prevent water scaling in pipes it is recommended to use lime softening at pH=10 which not only removes temporary hardness but enhances silicate ions removal by co-precipitation with Mg(OH)2 formed followed by filtration.

Nahied Shahbodaghi, Daryoush Afzali, Maryam Fayazi,
Volume 15, Issue 1 (4-2022)
Abstract

Background and Objective: With increasing water pollution, serious water shortages and increased pressure to save water, recycling and reuse of water has attracted more attention in various industries. Removal of silica from cooling water is essential for recycling and reuse of water. The aim of this study was to remove silica from water using magnesium oxide nanoparticles (MgO) synthesized by chemical deposition method.
Materials and Methods: Synthetic nanoparticles were successfully determined using field emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FTIR) and X-ray diffraction (XRD). To determine the optimal adsorption conditions the batch system, the effect of important parameters such as pH (2-8), contact time (0-150 min), initial concentration of silica solution (50-1000 mg/L), adsorbent amount (0.01-0.14 g) and temperature (25-60 ˚C) were studied.
Results: Under optimal conditions, an almost removal of 200 mg/L silica solution was achieved in 60 min reaction time. Equilibrium data were analyzed using the Langmuir and Freundlich isotherms. The adsorption process can be well described by the Langmuir model, and the maximum adsorption capacity was calculated as 75.76 mg/g. Synthetic data were analyzed using pseudo-first-order and pseudo-second-order equations. The pseudo-second-order model showed good agreement with the obtained data (R2 = 0.9949).
Conclusion: Due to the high potential of magnesium oxide nanoparticles in silica removal, it can be a good candidate for the removal of silica and industrial wastewater treatment.
 


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