Iranian Journal of

Background and Objective: The activities of various industries produce a wide range of pollutants and toxic compounds. One of these compounds is the catechol, a cyclic organic compound with high toxicity and resistant to degradation. Therefore, the purpose of this study was to investigate efficiency of powder activated carbon magnetized with Fe₃O₄ nanoparticles in the removal of catechol from aqueous solutions by response surface methodology.
Materials and Methods: The co-precipitation method was used to synthesize magnetic powder activated carbon and its properties were analyzed by SEM and XRD analysis. Then, the effect of the parameters such as pH, contact time, absorbent dose, initial concentration of catechol and temperature on the efficiency of adsorption process were investigated using a response surface methodology (Box–Behnken). The residual concentration of catechol was measured by HPLC at 275 nm.
Results: The results showed that the maximum efficiency of the adsorption process was obtained at concentration of 20 mg/L, pH=3, contact time 90 minutes, at 25 °C and absorbent dose of 1.5 g/L. The study of isotherm and kinetics showed that the experimental data of the catechol adsorption process correlated with the Langmuir and pseudo-second order models, respectively. Thermodynamic study of the reaction also expresses the Exothermic and Spontaneous process.
Conclusion: The results showed that the adsorption process using powder activated carbon magnetized with Fe₃O₄ nanoparticles at acidic pH had better efficiency. As a result, the studied process as an effective, rapid and inexpensive method for removal of catechol from aqueous solutions is proposed. Due to its short reaction time, it is economically affordable process.
 

Background and Objective: Heavy metals fixation in-situ by using inorganic amendments is a method for immobilization of polluted soils. The goal of this research was to determine efficiency of five amendments for heavy metals fixation of waste-water-irrigated soils around Tabriz city.
Materials and Methods: Cadmium, Pb, Cu, Ni, and Zn- containing solutions were added to 0.5 gram of five amendments including calcite, hematite, zeolite, illite, and bentonite. 10 soil samples from around of Tabriz city were taken. After shaking the samples, the concentrations of the five elements were determined in the filtered solution by using atomic absorption instrument. Retention capacity percentages of these elements were calculated, and the best amendments were determined by using Dunkan method.
Results: There were differences of heavy metals retention between amendments. Calcite had the highest retention of Cd (91%), Ni (78%), and Zn (94.7%); hematite had the highest Cu (90.5%) and Pb (94.3%); and illite showed the lowest retention of the 5 elements. Calcite, zeolite, bentonite, and hematite had significant higher retention capacities of Cd, Ni, and Zn in compared to 10 the soil samples.
Conclusion: Among the studied amendments, retention capacities of calcite and hematite for the five elements were higher than the remaining ones for addition to the soil. These two amendments can cause low uptake and low accumulation of the elements in agricultural crops in polluted soils.
 

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.

Background and Objective:  Arsenic has long been considered as a heavy metal and toxic pollutant due to its potential to harm the human health and the environment. Adsorption is one of the mechanisms for arsenic removal from wastewater. Therefore, the purpose of this research was to investigate the feasibility of synthesized chitosan-zirconium magnetic nano fiber on arsenic adsorption from wastewater and to evaluate its kinetic and isotherm models.
Materials and Methods: Synthesis of nanofibers was performed by electrospinning method and the optimal formulation was determined following the experimental design. Then, kinetics and isotherms of arsenic adsorption on the as synthesized nanofibers were investigated. The prepared nanofiber was characterized using X-ray diffraction (XRD), Field Emission Scanning Electron Microscopes (FESEM), Infrared Fourier Transform (FT-IR) and Vibrational Sampler Magnetic Meter (VSM).
Results: The optimal formulation was obtained: 2.84% chitosan, 0.97% nano-zirconium and 0.94% nano-iron. The adsorption of arsenic on synthetic fibers was found to follow quasi-first-order kinetics and the Freundlich isotherm. Furthermore, the effect of initial concentrations of arsenic, contact time, temperature and pH on arsenic adsorption were surveyed. The optimal condition for nitrate arsenic adsorption was obtained at initial concentration of 70 mg/L, 45 min contact time and at pH 3.
Conclusion: According to the results, the synthesized nanofiber displayed a regular network structure with the distribution of the Zr-nanoparticles in its shape. Also, according to the form of magnetometric analysis, it was found that chitosan-nanosirconium magnetic nanofibers are well magnetized and are free magnetic.  Finally, it can be concluded that the synthesized nanosorbent has a high potential for arsenic removal from industrial effluents.

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.

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.
 

Background and Objective: Antibiotics are emerging pollutants that enter the human environment through pharmaceutical, hospital, and urban wastewater. Therefore, this study was conducted to investigate of removal efficacy of tetracycline (TC) from aqueous solutions using GO@Fe₃O₄@β-CD.
Materials and Methods: In this descriptive study, GO@Fe₃O₄@β-CD was synthesized and then used as an adsorbent for the removal of TC from aqueous solution. GO@Fe₃O₄@β-CD was characterized using X-ray diffraction (XRD), Scanning electronic microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and vibrating sample magnetometry (VSM) methods. Also, the influence of variables including pH (3-9), amount of adsorbent (0.003-0.050 g), contact time (0-100 min), and temperature (25-55 °C) so assessed on the efficacy of TC removal. 
Results: The results of TGA analysis showed that GO@Fe₃O₄@β-CD nanoparticles were resistant to temperatures up to 400 °C. Also, the results indicated that β-cyclodextrin was uniformly dispersed on the surface of GO@Fe₃O₄.
The results indicated that removal efficiency increased up to 60 min contact time, 0.01 g of adsorbent, and decrease temperature to 25 °C. The optimum pH for TC removal was 7.0. Also, under these conditions, the adsorption process followed the Langmuir adsorption isotherm with a correlation coefficient of 0.992 and the pseudo-second-order kinetic model with a correlation coefficient of 0.997, 0.999, and 0.998. The maximum adsorption capacity of the prepared adsorbent was 357 mg/g.
Conclusion: The GO@Fe₃O₄@β-CD could be an effective and efficient adsorbent for the removal of TC from industrial wastewater.
 

Background and Objective: Due to the presence of industrial pollutants in water sources, it is necessary to treat wastewater, especially colored wastewater. This study aims to treat wastewater containing methyl orange dye using nano mesopore SBA-16.
Materials and Methods: In this study, the effect of different parameters (pH, concentration of methyl orange, amount of adsorbent, temperature, and contact time) on the absorption of methyl orange by nanocomposite prepared with the help of Design of Experiment 7 software and Response Surface Method (RSM) was investigated.
Results: The maximum amount of pollutant removal by the adsorbent was obtained under optimal conditions of pH = 4.07, temperature 50 °C, contact time 35 minutes, initial concentration of adsorbent 10 mg/L, and amount of adsorbent 0.04 g. Also, the findings showed that the absorption behavior is most consistent with the Langmuir isotherm and the absorption process is exothermic and spontaneous at low temperatures.
Conclusion: In optimal conditions, the SBA-16 adsorbent was able to remove 98.60 % of methyl orange from the aqueous solution and the maximum adsorption capacity (qmax) for the removal of methyl orange pollutant was 37.73 mg/g. Considering the high potential of nano mesopore SBA-16 in removing methyl orange pigment, it can be considered a suitable candidate for removing colored pollutants and treating wastewater from textile factories.
 

Background and Objective: Nowadays, the use of biochar as a new and suitable adsorbent to remove inorganic pollutants from water sources has grown significantly. The present study was conducted to evaluate the effects of biochar physical modifications compared to unmodified biochar on nickel (Ni) removal efficiency in aqueous solutions.
Materials and Methods: After the production of cypress cones biochar (RB), biochar particles (<164 µm) were crushed into very small (<26 µm) dimensions (BMB) using a planetary ball mill and after evaluation their various properties by SLS, BET, FTIR and SEM techniques, their application (RB and BMB) in optimizing the Ni removal from aqueous solutions were evaluated using the response surface methodology (RSM: Box-Behnken design).
Results: Based on the results, the physical modification of biochar (BMB) decreased the particle size by 6.2 times, increased the specific surface area by 4.9 times, increased (containing oxygen) and decreased (aliphatic and OH stretching groups) of specific functional groups and finer surface morphology, compared to RB. The use of BMB in the aqueous solution caused an increase of 9.7% (on average) in the removal of Ni compared to the RB sample. The fitting of the data obtained from Ni removal in the Box-Benken model in both adsorbents shows the appropriate prediction of this model in the optimization of Ni removal from aqueous solutions.
Conclusion: According to the results of this research, the physical modification of biochar, as a simple, cheap, and environmentally friendly method, due to the increase in the efficiency of Ni pollutant removal, can be introduced as a suitable method in the activation of biochar, which further research is required based on the type of biochar and various pollutants.
 

Background and Objective: Antibiotics as emerging pollutants are harmful to environmental health. Therefore, this study was conducted to investigate the efficiency of Uio-66-NH₂@CS-Iso-Gu nanohybrid for the removal of amoxicillin (AMX) from aqueous solutions.
Materials and Methods: In this study, for the first time, guanidine and isocyanate monomers are cross-linked with chitosan. The combination of this polymer with organometallic compounds contributes to its chemical/thermal stability and reusability. Uio-66-NH₂@CS-Iso-Gu nanohybrid was characterized using X-ray diffraction (XRD), Scanning electronic microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), Thermogravimetric analysis (TGA), and BET methods. Also, the effects of pH, initial concentration of AMX, contact time, and temperature were evaluated. Moreover, isotherm, kinetic and thermodynamics studies were performed.
Results: The results of TGA analysis showed that Uio-66-NH₂@CS-Iso-Gu nanohybrid was resistant to temperatures up to 400 °C. Also, optimal adsorption of AMX occurred in the first 25 min. The synthesized nanohybrid has a surface area of 101.2 m²/g and a type IV isotherm. Acidic groups were present on the synthesized nanohybrid surface based on the pHpzc = 4.7. Langmuir (for 25 °C and 45 °C) and Freundlich (for 65 °C) isotherm models and pseudo-second-order kinetic models are more appropriate to fit the adsorption data with the experimental data. The maximum adsorption capacity of the synthesized nanohybrid was equal to 56.49, 40.65, and 0.382 mg/g at temperatures of 25°C, 45°C, and 65°C, respectively. Based on the findings, Uio-66-NH₂@CS-Iso-Gu nanohybrid could be used for up to five cycles without significantly reducing their performance.
Conclusion: The results showed that Uio-66-NH₂@CS-Iso-Gu nanohybrid has a significant efficiency for removing AMX and could be used as an effective adsorbent for the treatment of wastewater containing pharmaceutical residues.