Showing 8 results for Adsorption
F. Golbabaei, E. Rahmanzadeh, G. R. Moussavi, A. Faghihi Zarandi, M. R. Baneshi,
Volume 4, Issue 2 (7-2014)
Abstract
Introduction: Chromium (VI) is a known human carcinogenic agent which is used in numerous industrial processes such as electroplating, welding, textile, cement and steel fabrication. The aim of this study was to determine the effectiveness of natural zeolite on the fixed bed adsorption of Cr (VI) from air stream.
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Material and Method: In this experimental study, chromium mists were generated by a nebulizer (3A model, Italy). Performance of natural zeolite in the Cr (VI) adsorption and its influencing factors such as air flow rate (1 and 3 L/min), the initial Cr concentration (0.05, 0.15, 1 and 10 mg/m3) and the bed depth (2.5, 5 and 10 cm) were investigated.
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Result: Zeolite adsorption capacity elevated by the increasing of bed depth but decreased with increasing of flow rate and inlet concentration. In order to facilitate the prediction of natural zeolite column performance Yoon-Nelson and Thomas models were used. The results showed that these models have a good agreement with our experimental data.
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Conclusion: Due to the extensive use of chromium in various industries and regulatory requirements related to workplace health and safety, Cr emission control in the occupational environment is essential. The adsorption process is one of the controlling measures of chromium emissions. The results indicated that natural zeolite has a high efficiency in Cr (VI) adsorption.
M. Jafarizaveh, H. Shirkhanloo, F. Golbabaei, A. Tabrizi, K. Azam, M. Ghasemkhani,
Volume 6, Issue 1 (4-2016)
Abstract
Introduction: Volatile organic compounds such as xylene are one of the main air pollutants. Adsorption method are of the most common methods used in the control of volatile organic compounds. The aim of this study was to investigate the xylene removal from air through nano activated carbon adsorbent in comparison with NIOSH approved carbon adsorbent.
Material and Method: Xylene adsorption tests on nano activated carbon and activated carbon in static mode (batch) were done in glass vials with volume of 10 ml. Gas chromatography with FID detector was used for analysis. Various variables including contact time, amount of adsorbent, concentration of xylene, and temperature were studied.
Results: Absorption capacity of xylene at ambient temperature (25° C) in static mode and duration of 10 minutes for activated carbon and nano activated carbon was obtained 349.8 and 435 mg/g, respectively. Results of Scanning Electron Microscope (SEM) images of nano activated carbon showed particle size pf less than 100 nm. Furthermore, Transmission Electron Microscope (TEM) pictures showed particle size of 30 nm. XRD images also showed cube structure of nano activated carbon adsorbent.
Conclusion: The results showed that adsorption capacity at constant humidity increased by raising in temperature and contact time. What is more, nano activated carbon absorbent showed greater absorption capacity for xylene removal compared to activated carbon absorbent
Akram Tabrizi, Farideh Golbabaei, Hamid Shirkhanloo, Mostafa Jafarizaveh, Kamal Azam, Rasoul Yarahmadi,
Volume 6, Issue 2 (6-2016)
Abstract
Introduction: Volatile organic compounds from industrial activities are one of the most important pollutants released into the air and have adverse effects on human and environment. Therefore, they should be removed before releasing into atmosphere. The aim of the study was to evaluate xylene removal from air by nano-grapheme and nano-graphene oxide in comparison with activated carbon adsorbent.
Material and Method: After preparing adsorbents of activated carbon, nano-graphene, and nano-graphene oxide, experiments adsorption capacity in static mode (Batch) were carried out in a glass vial. Some variables including contact time, the amount of adsorbent, the concentration of xylene, and the temperature were studied. Langmuir absorption isotherms were used in order to study the adsorption capacity of xylene on adsorbents. Moreover, sample analysis was done by gas chromatography with Flame Ionization Detector (GC-FID).
Results: The adsorption capacities of activated carbon, nano-graphene oxide and nano-graphene for removal of xylene were obtained 349.8, 14.5, and 490 mg/g, respectively. The results of Scanning Electron Microscope (SEM) for nano-graphene and nano-graphene oxide showed particle size of less than 100 nm. While, the results of Transmission Electron Microscope (TEM) showed particle size of 45nm for nano-graphene and 65 nm for nano-graphene oxide. Also, X-Ray Diffraction (XRD) showed cube structure of nano-adsorbents.
Conclusion: In constant humidity, increase in exposure time and temperature caused an increase in the adsorption capacity. The results revealed greater adsorption capacity of xylene removal for nano-graphene compared to the activated carbon, and nano-graphene oxide.
Elham Rahmanzadeh, Farideh Golbabaei, Ali Faghihi Zarandi, Seyed Gholamreza Moussavi, Mohammadreza Baneshi,
Volume 7, Issue 3 (9-2017)
Abstract
Introduction: Hexavalent chromium (VI) is a very strong oxidizing agent that, despite its many uses in various industries, duration of the exposure can lead to lung cancer, deep wounds (in the hands, arm, tongue and palate), nasal septum perforation, burning and inflammation in the nose, lung and upper respiratory tract, asthma, contact dermatitis, damage to the kidneys and liver, and skin allergy. This study aimed to determine the activated carbon efficiency in chromium adsorption (VI) from air flow and its effective parameters.
Material and Method: In this experimental study, chromium mists were generated by a nebulizer (3A model, Italy). Performance of activated carbon in the Cr (VI) adsorption and its influencing factors such as air flow rate (1 and 3L/min), the initial Cr concentration (0.05, 0.15, 1 and 10 mg/m3) and bed depth (2.5, 5 and 10 cm) were investigated. Yoon-Nelson and Thomas models were used to predict performance of adsorbent column and correlation test was used to determine accordance between the model and actual data.
Result: Activated carbon adsorption capacity increased with increasing of bed depth but decreased with increasing of flow rate and inlet concentration. The results showed that the Yoon-Nelson and Thomas models with a correlation coefficient above 0.9953 matched with the experimental data.
Conclusion: The results indicated that activated carbon has a high efficiency in Cr (VI) adsorption, so that its efficiency at flow rate of 3 L/m, depth of 5 cm and concentration of 20 TLV and TLV was 85.42 and 71.83 percent respectively.
Asghar Ghahri, Farideh Golbabaei, Leila Vafajoo, Seyed Mohammad Mireskandari, Mehdi Yaseri, Seyed Jamaleddin Shahtaheri, Faranak Najarian,
Volume 8, Issue 2 (6-2018)
Abstract
Introduction: Anesthetic gases used in hospitals include N2O and halogenated hydrocarbons (such as sevoflurane) which can be released through leakages and uncontrolled exhalation by the patient into the ambient air of clinical staff. These gases have greenhouse effect and damage to the ozone layer and serious risks such as reproductive, preterm delivery and fetal abnormalities and increased spontaneous abortion on the health of operating room personnel. Therefore, removal of these gases from the workplaces is essential especially in the treatment centers. The purpose of the present study was to investigate the adsorption of sevoflurane from air by using activated Charcoal and also the effect of acid modification on its performance.
Material and Method: In this study, two adsorbents of unmodified and modified activated charcoal with nitric acid were used to remove sevoflurane. After preparation, the adsorbents were characterized using XRD, FT-IR, BET and FE-SEM methods. After characterization, the breakthrough and adsorption capacity of sevoflurane on both adsorbents were determined using the modified wheeler equation.
Result: The results of characterization showed that acid modification did not affect the crystalline structure of activated charcoal and increased the adsorption and microporous of acid-modified activated charcoal in comparison with unmodified activated charcoal. It also reduces surface functional groups of the activated carbon. The results of determination of adsorption capacity indicated that the adsorption capacity of modified activated charcoal was improved in comparison with unmodified activated charcoal.
Conclusion: The results demonstrated that both adsorbents have the ability to absorb sevoflurane and modified activated charcoal have a better performance in this process. This effect may be due to the surface area of adsorption and volume of micro pores more than the unmodified activated charcoal.
Hojatolla Kakaei, Mojtaba Beygzadeh, Farideh Golbabaei, Mohammad Reza Ganjali, Mehdi Jahangiri, Sayed Jamaleddin Shahtaheri,
Volume 9, Issue 4 (12-2019)
Abstract
Introduction: Hydrogen sulfide is one of the most important impurities in natural gas. Due to the fact that this gas is hazardous, toxic, corrosive and volatile, therefore, the removal of hydrogen sulfide has been studied using several methods. One of the most known procedures is the adsorption process. In the present study, activated carbon and activated carbon-based composite scaffolds (MOF-5) were used as a cartridge mask to remove hydrogen sulfide from respiratory air.
Methods and Materials: First, activated carbon (AC) was converted to powder form by ball mill, and AC / MOF-5 composite with 10%, 25%, and 40% MOF-5 to AC was synthesized from the MOF-5 metal-organic scaffold. Then, the rates of adsorption and breakthrough time using a designed setup were tested in two ranges of temperatures, humidities and concentrations. XRD, SEM and BET were used to determine the properties of composite absorbents. The Aeroqual S500 Direct-reading sensor with 0.01 ppm accuracy was used to measure the exact amount of hydrogen sulfide gas.
Results: The AC/MOF-5 composite showed higher adsorption and breakthrough time compare to the other adsorbents. The Specific surface area (BET), average pore diameter, and total pore volume of the adsorbent were 814 m2 /g, 1.6795 nm, and 0.342 cm3 /g, respectively. The isotherm diagram showed that, according to IUPAC, most of the pore size of this adsorbent was classified in the micro-porous group. The maximum adsorption (mg/gS) and breakthrough time (min) were related to AC/MOF-5(40 Wt. %) adsorbent with 60.41 mg/gS (SD = 1.08) and 56.26 min (SD =2.38) at a temperature of 15 ° C, a concentration of 9.88 ppm (SD = 0.70), a moisture content of 51.06% (SD = 0.15) and a pressure drop of 51.34 mm water. By adding more than 25% MOF-5 metal-metal scaffold to activated carbon, the amount of adsorption, breakthrough time and pressure drop were increased.
Conclusion: AC / MOF-5 composite adsorbent due to its porous structure, high specific surface area, and most importantly, having Zn-O-C groups increased the adsorption rate as well as the pollutant Breakthrough time. However, it showed a relatively higher pressure drop than commercial activated carbon (AC).
Amir Hossein Khoshakhlagh, Farideh Golbabaei, Mojtaba Beygzadeh, Seyed Jamaleddin Shahtaheri,
Volume 11, Issue 4 (12-2021)
Abstract
Introduction: Toluene is considered as a group of chemical contaminants, causing problems for people’s health. Due to the high rate of evaporation and rapid emission in the surrounding environment, it leads to the exposure of many employees and people at risk and, subsequently, its irreparable effects on their health in different jobs. Therefore, its removal is very important. In the present study, this contaminant was removed using the copper metal-organic framework (MOF) under different operating conditions.
Material and Methods: In this study, the copper MOF was synthesized using the one-pot and in situ method. Physical and morphological properties of the adsorbent were investigated using BET, XRD, FTIR and SEM techniques. The efficiency of the adsorbent in removing toluene from the air stream under the dynamic adsorption system was investigated by examining the effect of the variables of adsorbent mass, pollutant concentration and humidity. Isotherm, thermodynamics and kinetics equations were used to evaluate the data.
Results: The results of experiments determining the properties of the metal-organic framework showed the formation of pure Cu-BDC crystals with mean and particle size distribution of 1.95 nm. The specific surface area calculated by the BET method for the mentioned sample was 686 m2 g-1 and the total volume of structural pores was 0.335 g3 cm3. The presence of micropores increased the dynamic adsorption capacity of toluene. The findings follow the Langmuir isotherm model and the Pseudo-second order kinetic model. Based on the results of thermodynamic studies, entropy change (ΔS°) and enthalpy change (ΔH°) were equal to -0.44 kJ mol-1 K-1 and -15.67 kJ mol-1, respectively. Gibbs free energy change (ΔG°) was also calculated negatively, indicating that the adsorption process was spontaneous and exothermic. The regeneration of the adsorbent was 77% after three cycles.
Conclusion: According to the results of this study, the microporous copper MOF can be used as a result of cheapness, high access, high adsorption capacity and appropriate regeneration rate in different operating conditions for adsorption of toluene.
Akram Tabrizi, Mostafa Jafarizaveh, Hamid Shirkhanloo, Farideh Golbabaeie,
Volume 14, Issue 4 (12-2024)
Abstract
Introduction: Volatile organic compounds (VOCs) are hazardous toxic pollutants in the air, which are released from various industrial sources. Due to the adverse effects of xylene on health, the effective removal of VOCs from the air by nano sorbents is crucial. In this study, nanographene (NG) and nanographene oxide (NGO) were used as adsorbents to investigate the efficiency of xylene removal.
Material and Methods: In this study, in order to investigate the absorption efficiency of nanographene and nanographene oxide after the synthesis of nano absorbents in a dynamic system, xylene vapor was produced in a chamber in pure air and stored in a Tedlar sampling bag and then transferred to the adsorbent. Subsequently, the effect of various parameters such as xylene concentration, inlet air flow rate, and absorbent mass values at 32% humidity and 25°C temperature on the absorption rate and performance of the desired absorbents was investigated. Finally, the gas chromatographic flame ion detector (GC-FID) determined the concentration of xylene in air after the adsorption-desorption process.
Results: The average adsorption efficiencies for NG and NGO were found to be 96.8% and 17.5%, respectively. The characteristics of the NG and NGO adsorbents indicated that the particle size range was less than 100 nanometers.
Conclusion: The results demonstrated that the adsorption efficiency of NG for the removal of xylene from the air is higher than that of NGO. The GC-MS method validated the proposed approach in real air samples.
