F. Golbabaei, R. Moradi Rad, L. Omidi, S. Farhang Dehghan, S. Roshani,
Volume 5, Issue 2 (7-2015)
Abstract
Introduction: Polycyclic aromatic hydrocarbons (PAHs) are one of the most significant current environmental issues. Phenanthrene and naphthalene adsorption at activated carbon beds prevent the release of these compounds into the environment. The objective of this research was to compare the amounts of phenanthrene and naphthalene adsorption at activated carbon beds in the n-hexane solution.
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Material and Method: This discontinuous experimental study was conducted in the laboratory scale batch and in the n-hexane solution containing phenanthrene and naphthalene.PH values were adjusted by adding hydrochloric acidand 1 N NaOH. The initial and residual phenanthrene and naphthalene concentrations were spectrophotometrically measured at 270 and 266 nm, respectively.
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Results: Findings showed that the maximum adsorption of naphthalene was obtained at pH=5 and contact time of 8 hours (7.4 mg/gr). The maximum adsorption was reached at pH=7 and contact time of 11 hours for phenanthrene (8.34 mg/gr).Improvement in the adsorption capacity was happenedby the increases in contact time and initial phenanthrene and naphthalene concentrations. The adsorption kinetics of these two compounds followed pseudo-second-order and Freundlich isotherm model.
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Conclusion: Freundlich isotherm model showed a strong association with PAHs adsorption process. A weak correlationwas observed between Langmuir theory and the results of the adsorption at activated carbon beds in the organic n-hexane solution.
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.
