Showing 11 results for Adsorption Isotherm
A Maleki, A Eslami,
Volume 3, Issue 4 (1-2011)
Abstract
Backgrounds and Objectives:Water contamination with arsenic has been recognized as a serious problem and its epidemiological problems to human health have been reported. The objective of this study was to explore the possibility modified wheat straw using sodium bicarbonate for removing arsenic from aqueous solution.
Materials and Methods: Adsorption process was accomplished in a laboratory-scale batch with emphasis on the effect of various parameters such as pH, contact time, arsenic concentration and adsorbent dosage on adsorption efficiency. In order to understand the adsorption process, sorption kinetics and equilibrium isotherms were also determined.
Results: It was found that adsorption of the arsenic was influenced by several parameters such as arsenic initial concentration, adsorbent dosage and solution pH. Maximum absorption efficiency was achieved at pH 7. As expected the amount of arsenic adsorbed on wheat straw incresed as its concentration went up. Among the models tested, namely the Langmuir, Freundlich, and Dubinin Radushkevich isotherms, the adsorption equilibrium for arsenic was best described by the Langmuir and Freundlich models. It was also found that adsorption of arsenic by wheat straw followed pseudo second-order kinetics. Mean free energy of adsorption (15.8 kJ mol-1) indicates that adsorption of arsenic by wheat straw might follow a chemisorption mechanism. Desorption studies show that arsenic ions are strongly bounded with the adsorbent and exhibit low desorption.
Conclusion: It is concluded that that adsorption by modified wheat straw is an efficient and reliable method for arsenic removal from liquid solutions.
K Naddafi, R Nabizadeh Nodehi, M Jahangiri Rad,
Volume 3, Issue 4 (1-2011)
Abstract
Backgrounds and Objectives: Anthraquinone dyes such as reactive blue29 in water resources and industrial wastewater effluents are one of the most environmental setbacks in many countries. Various methods have been considered to remove these dyes One of which is adsorption.
Materials and Methods: All adsorption experiments were conducted in different pHs and various concentrations of adsorbents. The initial concentration of reactive blue 29 chosen in this study was 30mg/L.Adsorption isotherms were determined and correlated with Longmuir, Freundlich and BET models.
Results: The maximum adsorption capacity of reactive blue 29 onto single wall carbon nanotubes was 496mg/g.Results showed that the best pH for adsorption was 5 followed by pH3 and 8. Kinetic study showed that the equilibrium time for adsorption of RB 29 to SWCNT is 4 hr.
Conclusion:According to the results obtained BET isotherm fitted well the experiment. It shows the adsorption of reactive blue 29 onto single wall carbon nanotubes is multilayers and the mechanism of SWCNTs adsorption toward RB29 is based on weak van der waals forces.
Afshin Maleki, Amir Hossein Mahvi, Reza Rezaee, Behrouz Davari,
Volume 5, Issue 4 (2-2013)
Abstract
Background and Objectives: Dyes are an important class of pollutants, which can even be identified by naked eye. Disposal of dyes in precious water resources have been prohibited, however, various treatment technologies are in use. Among various methods adsorption occupies a prominent place in dye removal. Therefore, natural zeolite (clinoptilolite) and acid modified zeolite were used as a low-cost adsorbent to evaluate their ability to remove color from aqueous solution using a batch adsorption experiments.
Materials and Methods: Modification of zeolite surface was carried out with two acids sulfuric acid and phosphoric acid, to improve the removal efficiency of reactive blue 19. We studied the influence of acid concentration, contact time, solution pH, initial dye concentration, and adsorbent dosage on the removal efficiency.
Results: The parameters of Langmuir and Freundlich adsorption isotherms have been determined using the adsorption data. Equilibrium adsorption data followed both Langmuir and Freundlich isotherms. It was also found that adsorption of dye by zeolite followed pseudo first-order kinetics. The adsorption results indicated that natural zeolite has a limited adsorption capacity for reactive dye but can be distinctly improved by modifying its surfaces with acid. Experimental results also showed that sulfuric acid has better performance than phosphoric acid in the modification of zeolite for dye adsorption.
Conclusion: We achieved the best results in terms of removal efficiency (41-72%) for the zeolite modified with Si/Al ratio of 7.5 after 3 h of contact.
Hafez Golstanifar, Simin Nasseri, Amir Hossin Mahvi, Mohamad Hadi Dehghani, Anvar Asadi ,
Volume 5, Issue 4 (2-2013)
Abstract
Background and Objectives: The contamination of nitrate (NO3−) in groundwater resources causes two adverse health effects: induction of “blue-baby syndrome” (methemoglobinemia), especially in infants, and the potential formation of carcinogenic nitrosamines. The aim of this research is to investigate nitrate removal from groundwater using alumina nanoparticles and to determine the adsorption isotherms.
Materials and Methods: This analytical-descriptive study was carried out at lab-scale, under batch conditions, and at room-temperature. The structure of alumina nanoparticles was determined using XRD, SEM, and TEM techniques. The concentration of nitrate in the solutions was determined by spectrophotometer at wavelengths of 220 and 275 nm. In addition, we investigated the impact of the important operational parameters including initial dose of Al2O3 (0.06-0.25 g/l), initial concentration of the solution (50- 300 mg/l), contact time (5-60 min), and pH (3-9). Moreover, we used Freundlich and Langmuir isotherm models to calculate equilibrium constant.
Results: It was found that nitrate removal efficiency increased as we increased contact time, initial concentration and pH in batch system. A maximum of 60% nitrate removal was achieved under following conditions: 60 min contact time, pH 5, and initial nitrate concentration of 300 mg/l as N. The obtained results showed that the adsorption of nitrate by Nano-Gamma-Alumina follows Langmuir isotherm equation with a correlation coefficient equal to 0.982.
Conclusion: Overall, our findings showed that the alumina nanoparticles can be used as an effective adsorbent to remove NO3 from aqueous solutions.
Elnaz Iravani, Mohammadhadi Dehghani, Amirhossein Mahvi, Noushin Rastkari,
Volume 6, Issue 2 (9-2013)
Abstract
Background and objectives: Bisphenol A (BPA) is an endocrine disrupting chemical that releases to the environment through effluents of its producing factory, pulp and paper mill factories, and plastics industry. The purpose of this study was to investigate adsorption isotherms of removing BPA from aqueous solutions using single walled carbon nanotubes (SWCNTs).
Materials and methods: This study was an empirical investigation. Our experiments were conducted discontinuously using 50 mL of sample in each test. The variables of this study were the contact time (5, 15, 30, 60, 90, 120 min), the initial concentration of BPA (2, 5 , 20, 50 mg/L), and pH (3, 5, 6, 9, 11). The concentrations of BPA were measured using UV-Vis spectrophotometer.
Results: The maximum adsorption capacity was found to be 71.42 mg/g. The results of our experiments showed that maximum adsorption capacity at equilibrium was achieved at t = 60 min and pH = 9. Moreover, increasing the initial concentration is associated with an increase in adsorption capacity until it becomes constant.
Conclusion: The BPA adsorption on SWCNT follows Freundlich-Langmuir isotherm.
Mohammad Ali Baghapour, Babak Jahed, Gholam Hossein Joshani,
Volume 6, Issue 3 (12-2013)
Abstract
Background and Objectives: Increasing waste tiers production has made the recycling of this solid waste a critical issue in the world. On the other hand, it seems contamination of groundwater to the petroleum pollutant like gasoline is a great threat to the health of societies in developing countries. The main objective of this study was gasoline removal from aquatic environment by waste tire derived activated carbon.
Materials and Methods: In this study for preparation of activated carbon from waste tires, KOH was used for chemical activation process. We used argon gas to prevent precursor oxidation . We applied N2 gas and BET isotherm for characterization of the prepared activated carbon texture. Isothermal and kinetic models were used for defining gasoline adsorption characteristic to adsorbent, and thermodynamic studies were used to determine the effect of temperature.
Results: Characterization results revealed that SBET and VTOTAL were 111.702m2/g and 0.124cc/g respectively. Langmuir and pseudo-second order models were the best isotherm and kinetic models for prediction of the adsorbent behaviors to adsorb gasoline. The Gibbs free energy changes were negative at all temperatures applied.
Conclusion: Produced activated carbon has desired surface area and adsorptive capacity for gasoline adsorption in aquatic environments and it seems preparation activated carbon from waste tiers is cheap, effective and environment friendly.
Mohammad Malakootian, Laleh Ranandeh Kalankesh,
Volume 6, Issue 4 (3-2014)
Abstract
Background and Objective: Humic substances in drinking water react with chlorine and form carcinogenic compounds. Humic acid is a principal component of humic substances and its separation from surface waters is crucial. Adsorption process is among different methods for separation of humic acid from surface waters and because of its simple and economical nature it has attracted considerable attention. The aim of this research was to examine performance of silicon nanoparticles in adsorption of humic acid in water. Materials and Methods: Experimental study was conducted on both synthetic and real water samples collected from Zarrineh Rood River, Tabriz before its entrance to water treatment process. We used instantaneous sampling method.The chemical quality of crude sample and its humic acid was determined and then the influence of pH, absorbent amount, and time on the removal of humic acid was evaluated. Therefore, the optimal conditions for each of these parameters were determined. In order to get better insight into the process of adsorption, the adsorption kinetic and equilibrium isotherm were studied. We measured humic acid concentration and TOC using spectrophotometer (Shimadzu /UV-1800, Japan) at a wavelength of 254 nm and TOC analyzer (Shimadzu model TOC-VCSH) measured. SPSS software and regression were used for data analysis. Results: At pH=4, retention time of 10 minutes, adsorbent amount of 0.25 g/L, we found that the highest percentage of humic acid adsorption was 88.4 and 81.8 for synthetic and real solutions respectively. The finding revealed that the removal of humic acid follows Freundlich isotherm ( =0.8172) and the second order kinetic model ( =0.9936). Conclusion: Removal in both real and synthetic solutions was less due to the reaction of influencing factors. However, considering the high percentage of humic acid removal under optimal conditions and its comparison with other methods, the removal of humic acid using SiO2 can be considered as an efficient method.
Mohamad Hadi Dehghani , Mamood Alimohammadi , Amir Hossein Mahvi, Noushin Rastkari, Masoome Mostofi, Maryam Gholami ,
Volume 6, Issue 4 (3-2014)
Abstract
Background and Objective: Various industries such as petrochemical, oil refinery, pharmaceutical, plastics, paper, steel and, resin produce a substantial of phenol and its derivatives. Wastewaters containing phenol need careful treatment before discharging into the environment due to their poor biodegradability and high toxicity. The objective of this study was to remove phenol by multiwall carbon nanotubes from aqueous solution. Materials and Methods: Adsorption process was implemented in a laboratory-scale batch with emphasis on the effect of various parameters such as contact time (5 to 120 minutes), pH (3- 11), initial concentration of phenol (5 - 50 mg/l) and the sulfate and chloride ions (20 - 200 mg/l) on adsorption process. To achieve a better realization of adsorption process, sorption kinetics and equilibrium isotherms were also determined. Results: The results indicated that maximum adsorption capacity occurred at concentration 50 mg/L and t =30 minutes. The uptake fluctuated very little in the pH range of 3–9, and at greater than 9 the absorption decreased suddenly. Moreover, the presence of sulfate and chloride ions had no effect on the process. It was found that adsorption kinetics and equilibrium data follow a pseudo-second-order kinetics model and a Freundlich isotherm model respectively. Conclusion: It is concluded that carbon nanotubes being effective in a wide range of pH, short time to reach equilibrium and the absence of competing ions on the absorption process can be used effectively in removing phenol from aqueous solution.
H Zarei, A.h Mahvi, S Nasseri, R Nabizadeh Noudehi, F Shemirani,
Volume 8, Issue 3 (12-2015)
Abstract
Objective and Background: Fluoride is an element widely found in the earth crust. Advantages and disadvantages of fluoride in the human body are depended on its concentration. Long-term consumption of drinking water contaminated with arsenic can cause adverse health effects such as skin lesions and cancer in humans. The aim of this study was to study efficiency of nano alumina on multi walled carbon nano tube for removal As(V) and fluoride from aqueous solution.
Materials and Method: In this study, nano-scale crystalline alumina was synthesized on single walled carbon nanotube by sol-gel method for using as a sorbent for solid phase extraction of Fluorine ion and arsenic(V). Response surface methodology based on Box-Behnken was used to assess the effect of independent variables on the response function and prediction of the best response value. In this study, effect of different parameters, such as contact time (10 to 120 min), pH (3-9), adsorbent dosage (0.25-1.5 g/L) and initial concentration of fluoride (2-8 mg/L) on efficiency of process was investigated. The structure of nano-scale alumina on multi walled carbon nano tube was determined by XRD and SEM techniques. Moreover, Freundlich and Langmuir isotherm models were used to calculate equilibrium constant.
Results: It was found that by increasing contact time and adsorbent dosage the rate of fluoride removal increased. However, by increasing pH and initial concentration the efficiency of fluoride removal decreased. High value for R2 (0.94) shows that removal of arsenic(V) can be described by this model. The Freundlich isotherm was the best fitted graph for experimental data with R2 more than 0.997.
Conclusion: In this study, it was observed that efficiency of arsenic(V) and fluoride removal was greatly increased by using nano-scale alumina on multi walled carbon nanotubes (MWCNTs).
M Nourinejad, N Arsalani, H Namazi,
Volume 10, Issue 1 (6-2017)
Abstract
Background and Objective: Nicotine as the most toxic alkaloid in tobacco is one of the compounds which causes human death over the past few decades. The purpose of this paper was to remove nicotine environmental pollution from aqueous solutions using halloysite-polythiophene nanocomposite.
Materials and Methods: Halloysite-polythiophene nanocomposite was prepared using a homogeneous solution of HNT and FeCl3 at 0-5°C by the ball milling technique. In this study, parameters such as pH, contact time and initial concentration of nicotine in laboratory scale were studied and the physical properties of the adsorbent were characterized via fourier transform infrared (FTIR) and scanning electron microscopy (SEM). Then, the absorption results were described using Langmuir and Freundlich isotherms.
Results: The results showed that the pH, initial concentration of nicotine and contact time had a direct effect on the nicotine adsorption process. The adsorption of nicotine followed Langmuir isotherm (R2 < 0/995). Moreover, the best adsorption result was achieved at pH=7, 50mg adsorbent, contact time of 90 min and 50mg/L of nicotine.
Conclusion: The results of this study showed that the Halloysite modification as a mineral composite with polythiophene and the synthesis of HNT@PTh nanocomposite can be used as an effective adsorbent to adsorb the nicotine.
H Niknejad, M Farzadkia, A Esrafili, M Kermani,
Volume 12, Issue 4 (2-2020)
Abstract
Background and Objective: 2,4 dinitrophenol is observed in sewage produced from chemical and petrochemical industries. Contamination of drinking water with these pollutants causes toxicity, health problems and change in taste and odor. The present study was developed to evaluate the efficiency of removal 2,4-DNP through dried sludge adsorbent and modified calcium chloride sludge adsorbent.
Materials and Methods: At first, sludge was dried at temperature of 60 °C. Next, CaCl2 was used to improve adsorption capacity. The removal efficiency of 2,4 dinitrophenol were determined by HPLC at wavelength of 360 nm. The effects of influencing factors including pH, initial pollutant concentration, contact time, and adsorbent dose were examined.
Results: The optimum pH of adsorption for both adsorbents was found to be 7. The optimum concentration of 2,4-DNP was 10 ppm. The results obtained from the present research showed that the removal of the contaminant using dried and modified sludge sorbent was increased from 72.6% to 86% at a dosage of 1.5 g. The adsorption kinetics were fitted with the pseudo second order kinetics model for both adsorbents. The isotherm data also showed that the adsorption of this pollutant on both adsorbents is fitted with the Freundlich model.
Conclusion: Results obtained from the present study indicated that the efficiency of the modified sludge ash is more than the non-modified sludge in 2,4 dinitrophenol removal. This can reduce adsorbent consumption in industrial treatment plants.
