Iranian Journal of Chemical Engineering (IJChE)

Abstract Heavy metals are among the most hazardous pollutants released into the environment through industrial activities. In recent years, adsorption has been recognized as an effective method for the removal of metal ions from wastewater. Ultrasonic irradiation is a promising technique for intensifying mass transfer during adsorption. In this study, the effect of high-frequency ultrasonic waves on the enhancement of nickel (II) ion removal from aqueous solutions using Fe₃O₄ nanoparticles was investigated. The influence of adsorbent dosage, contact time, and pH on removal efficiency was examined and optimized using response surface methodology (RSM). The maximum removal efficiency achieved with the ultrasonic-assisted process was 84.3% at 60 minutes of contact time, 8 g of Fe₃O₄, and pH = 5, while the conventional stirring (shaker) method resulted in a maximum efficiency of 79.54% at 100 minutes, 10 g of adsorbent, and pH = 9. The use of ultrasound significantly accelerated the adsorption rate at the initial stages by generating cavitation and microstreaming, which increased the availability of active surface sites on the nanoparticles. These findings demonstrate that the combination of Fe₃O₄ nanoparticles and ultrasonic irradiation offers a rapid, efficient, and environmentally friendly approach for the removal of nickel (II) ions from industrial wastewater.

Abstract A low cost and environmentally friendly process for the synthesis of the disodium salt of hydroquinone (DSH) is presented. This novel synthesis technique employs water as solvent. Compared to the well-established synthesis techniques which utilize methanol, the presented technique is safer and environmentally friendly. First, a DSH sample is synthesized using the customary synthesis technique by employing methanol as solvent. Then, the technique introduced in this study is implemented under three different scenarios differing in the way the drying step is performed. The resulting DSH powders are then compared using FTIR  analyses. It is shown that all the synthesis techniques yield acceptable results, However, drying at higher temperatures yield better results. Furthermore, the crystal structure of the DSH sample is investigated using an XRD analysis and compared to the simulated diffraction pattern of DSH. The results indicate the correct synthesis of DSH. Finally, a DSC-TGA test is performed to further confirm the correct synthesis of DSH.

Abstract The preparation of ethylcellulose (EC) nanofibers (NFs) by the electrospinning method was optimized by Taguchi design. A Taguchi design was performed for electrospinning parameters such as EC concentration, voltage, ethanol/water ratio in the solvent, and feed rate in four levels (array L16).  EC solutions with a certain concentration were prepared in ethanol-water solvents with a certain ratio. The solutions were then stirred at a constant temperature for four hours and left overnight. Electrospinning parameters such as temperature 30 ˚C, distance between syringe needle and collector 10 cm, aluminum foil 20 micrometers as collector, collector speed 400 rpm, and electrospinning time 2.5 hours are constant in all electrospinning experiments, but voltage and feed rate were changed according to the experimental design. The resulting EC fibers were imaged by scanning electron microscopy (SEM). The SEM images of EC fibers were processed by Image J software, and the average diameter of EC fibers in each experiment was calculated. The results of the diameter of the electrospun EC fibers showed that all the fibers had a diameter of less than 100 nm. Also, the results of the diameter of EC fibers were analyzed based on the analysis of variance, and it was found that the ethanol/water ratio in the solvent (34.9%), the feed rate (23.5%), the voltage (22.1%), and the EC concentration (17.5%), respectively, had the greatest contribution to the diameter of EC fibers. Under optimal conditions, EC fibers with a diameter of 41 nm were prepared.
 

Abstract In this study, carbon nanotubes were fully aligned by chemical vapor deposition at atmospheric pressure on a silicon substrate at two carbon source flow rates of 28 and 38 sccm (standard cubic centimeter per minute). Acetylene gas (C₂H₂) as the carbon source for argon gas (Ar) as the carrier gas for hydrogen gas (H₂) for the recovery of the nanoparticle and iron nanoparticles as the catalytic source at 800 °C were used for the growth of the carbon nanotube array. The reaction was carried out in a 48 cm long quartz tube and the gases were injected with specified flow rates. The silicon substrate was coated by the magnetic sputtering method with catalytic iron nanoparticles with a thickness in the range of 3-6 nm. The results of the FESEM analysis showed, as the carbon source flow rate was increased to 38 sccm, the average diameter of the grown carbon nanotubes is increased, and the carbon nanotubes with a diameter of 60-70 nm were most abundant.

Abstract In this work, nanoparticles of the metal fuel Zirconium (Zr) and nanoscale oxidizer BaCrO₄ are synthesized considering their unique nanoparticle characteristics like mixing homogeneity and high surface/volume ratio. Using the synthesized fuel and oxidizer, the pyrotechnic mixture of Zr/BaCrO₄ was developed under 4 different conditions and analyzed in terms of the thermal behavior and burning rate. In the synthesis stage, the oxidizer nanopowder BaCrO₄ was developed through precipitating Barium Nitrate and Chromate Potassium in the vicinity of Dodecyl benzene sulfonate sodium (DBSS) stabilizer. Also, Zr nanopowder was prepared using direct reduction of Zr (NO₃)₂ by N₂H₂ and was coated by a 4% Collodion. Then, the pyrotechnic mixture Zr/BaCrO₄ was charged and pressed in the constructed combustion chamber. The burning rate of the mixture was captured by the direct footage of the combustion process using digital cameras with 60 frame-per-second capabilities. The fastest burning occurs when both the fuel and the oxidizer are nano-scaled. The thermal behavior of the mixture was studied using the simultaneous thermal analysis (STA) machine within the temperature range of 25 to 1000 °C. Results of the thermal analysis show that the thermal decomposition temperature of the Zr/BaCrO₄ mixture in the micron size is higher than in the nano size and the amount of destruction is lower. Increasing the concentration of zirconium in the nano-size from 10 to 50% leads to a decrease in the decomposition temperature from 565 to 437 °C, while the pyrotechnic mixture destruction rate increases from 39% to over 63%.

Abstract 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane (HMX) is one of the most powerful explosives of which the purity may have a significant effect on increasing the performance of rocket engines. In this research, the synthesis of high purity HMX is presented using the nitration of 1,5-diacetyl-3,7-dinitrooctahydro-1,3,5,7-tetrazocine (DADN) with a mixture of nitric acid and polyphosphoric acid. The nitration parameters including temperature, time, and the concentration of nitric acid, and polyphosphoric acid were optimized for the desirable purity and efficiency using the response surface method and central composite method (CCD). Based on the optimization, HMX was obtained with a purity of 99% and an efficiency of 92.9% at a temperature of 70°C and the time duration of 70 minutes with a molar ratio of polyphosphoric acid to nitric acid of 1:1:6.

Abstract The chemical interesterification (CIE) process is a promising approach to modifying and improving oils and fat structure. In this study, CIE of fully hydrogenated soybean oil (FHSO) and sunflower oil (SFO) was performed. Different initial blends with various mass ratios of 20-45% FHSO (coded as S1, S2, S3, and S4) were converted to interesterified samples (Si-1, Si-2, Si-3, and Si-4, peer-to-peer). The interesterified samples (60% content) were used in different margarine formulas with 40% palmolein PO (M1, M2, M3, M4), and margarines enriched with beta-carotene, to compensate for the reduction of carotene during the oil decolorization process during refining. Esterification caused a significant decrease in the solid fat content (SFC) of initial fat blends and fatty acid profile analysis confirmed just less than 0.17-0.3% of trans fatty acid content (According to the definition of zero trans less than 0.5 g/12 g serving). Differential scanning calorimetry (DSC) measurement indicated that the interesterified samples possess lower melting points while showing binary or ternary crystallization peaks. The Polarized light microscopy (PLM) confirmed the presence of fine, desirable β´spherulite crystals, which are effective in creating the proper texture in margarine. Formulated margarines were evaluated and compared with one type of commercial margarine (as a control sample). According to the texture profile analysis (TPA) and organoleptic results, the M3 formula was chosen as the best formulation for margarine preparation (using Si-3 blending with the 35: 65 ratios of FHSO to SFO).

Abstract It is crucial to design and develop new polymers with desirable characteristics. Aromatic polyimides have been attracted more attention in comparison with other polymeric materials, because of their excellent properties, such as the high thermal stability, mechanical strength, and chemical resistance. In this work, two semi-aromatic polyimides (BCDA-mPDA and BCDA-Durene) were successfully synthesized from bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarbocylic dianhydride (BCDA), 1,3-phenylenediamine (mPDA), and 2,3,5,6-tetramethyl-1,4-phenylenediamine (Durene) to investigate the effect of methyl functional groups on the physicochemical and structural properties of the synthesized polyimides. The synthesized polyimides were characterized by the proton nuclear magnetic resonance (¹H-NMR) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) spectroscopy, inherent viscosity measurement, and solubility test. FTIR and ¹H-NMR results confirmed the chemical structure of the synthesized polyimides. XRD results showed that the presence of bulky methyl groups has led to increasing amorphous regions in the polymer structure. In addition, these new polymers were soluble in various organic solvents such as dimethylformamide (DMF), dimethylsulfoxide (DMSO), and N-methyl-2-pyrrolidone (NMP). The inherent viscosity of the synthesized polyimides was 0.65 dl/g for BCDA-Durene and 0.96 dl/g for BCDA-mPDA, which indicates the moderate molecular weight of the polymers.

Abstract Potassium superoxide tablets can be used in respiratory air regeneration systems within confined spaces such as spacecraft, submarines, coal mines and individual and collective masks. These tablets react with moisture and carbon dioxide in air and release oxygen. In this study, The effect of five parameters; the pressing pressure (0.5, 2, 4 and 5 bar), humidity (10, 15, 20, 25 %), Catalyst additives (CuSO₄.5H₂O, (Cu₂(OH)₃Cl₂)₂, CuO, TiO₂), H₂O Absorbent additives  (SiO₂, LiCl, CaO, SiO₂.Al₂O₃) and CO₂ Absorbent additives (LiOH, NaOH, KOH, Ca(OH)₂) were investigated in four levels using the Taguchi method. The carbon dioxide absorption and Surface Erosion were selected as criteria for optimizing the performance of Potassium Superoxide tablets based on the analysis of variance and the optimal conditions of each were evaluated separately and simultaneously. The optimal conditions for the higher carbon dioxide absorption and smaller Surface Erosion include the Humidity of 15 %, pressing pressure of 4 bar, CuSO₄.5H₂O as the Catalyst, SiO₂ as the H₂O absorbent and Ca(OH)₂ as the CO₂ absorbent. Experiments performed in the performance test show that the optimized tablets in this study show a 28 % and 79 % increase in the carbon dioxide absorption compared to commercial tablets and pure potassium superoxide respectively. The results showed that the catalysts with copper cation had the greatest effect on the performance of the tablets.
 

Abstract  Magnetorheological fluids contain suspended magnetic particles that arrange in chains in the presence of a magnetic field, causing the conversion of the fluid from a liquid state to a quasi-solid state. These fluids can be used in valves as a tool for pressure drop and flow interruption. This research aims to investigate the feasibility of using magnetorheological fluid (MRF) in industrial valves. The rheological properties of the MRF sample were measured with the MCR300 rheometer in the presence of a magnetic field. In this connection, the Bingham plastic continuous model was used to predict fluid behavior, and model coefficients were obtained using MATLAB software. Then, the model's coefficients were used to simulate the behavior of the magnetorheological fluid in the presence of the magnetic field in the valve. The geometry and dimensions of the valve were designed according to the dimensions of industrial samples. Then the CFD simulation with Fluent software was done by using the Bingham model and fluid characteristics obtained from experimental results. The results showed that the pressure increased by increasing the magnetic field at the center of the sleeve. The magnetic field up to 0.5 Tesla, increases pressure and decreases amplitude. Therefore, as the magnetic field increase, the amplitude of the maximum pressure on the sleeve was significantly reduced.

Abstract Many industries produce large volumes of effluent which are made of oil and its derivatives; very common pollutants in the environment. The use of hydrophobic magnetic particles due to their low cost, low toxicity, and availability is one of the preferred methods for separating oil from water in oil spillage issues. This research aims at evaluating the effects of dopamine as a link in the hydrophobicity of carbonyl iron (CI) particles with stearic acid. In this connection, CI @ stearic acid and CI @ dopamine @ stearic acid have been synthesized. The FESEM analysis was used to observe the surface modification and structure of the particles. The magnetic properties of hydrophobic particles were also measured and the magnetic saturation of CI, CI @ stearic acid, and CI @ dopamine @ stearic acid were 200, 169, 131 emu/g respectively. Finally, the contact angle and adsorption capacity of two modified particles were measured. Based on the result, the static contact angles of water drops placed on the beds of the CI, CI @ stearic acid, and CI @ dopamine @ stearic acid were found to be 0°, 162.9°, and 168.24° respectively. The adsorption capacity range for CI@ stearic acid particles was 1.5 to 2.2 and for CI@ dopamine@ stearic acid particles was 1.8 to 3.2. Therefore, the result showed that dopamine had a good effect as a link to the hydrophobicity of carbonyl iron particles.

Abstract In this work, the phosphate bonded refractory was developed using magnesium potassium phosphate cement. The Cement was prepared from the caustic calcined magnesium oxide with the addition of mono potassium phosphate. The characterization of the cement was done by XRD and SEM to examine the change in phase and morphology which occurs after the hydration of magnesium potassium phosphate cement which is in the struvite phase. To evaluate the physical, mechanical and thermal properties, refractory samples were casted and subsequently dried and fired at temperatures ranged from 1300 °C to 1500 °C. The effect of temperature on the bulk density, apparent porosity and crushing strength were analyzed. It was found that the properties of the chemically bonded refractory were better than the conventionally bonded calcium alumina cement refractory.

Abstract In this work, for eliminating the (RR1346), considered to be a waste in wastewater from dye industries electrochemical advanced oxidation process has been used. Graphene oxide coated carbon cloth (GO/CC) and Fe3O4 /GO coated carbon cloth (Fe3O4/GO/CC) electrodes has been fabricated by synthesized GO and Fe3O4 nanoparticles. Characteristic properties such as surface morphology as the main reason of utilizing Fe2O3/GO/CC as electrodes has been investigated determined by various instrumental analysis including, Atomic Force Microscopy (AFM), Field Emission Scanning Electron Microscopy (FESEM), Cyclic Voltammetry (CV), Cathodic polarization, and also for investigating the process yield by utilization of mentioned electrodes, UV-vis spectrophotometric analysis has been used to determine dye concentration in sample waste water, after comparing fabricated electrodes removal efficiency in same time intervals, by determining the concentration of RR1346 dye in samples after oxidation process in different time intervals, results indicated better removal efficiency Fe3O4/GO/CC fabricated electrode than the other two electrodes, which this conclusion was proved by AFM,FESEM and UV-vis results.

Abstract Abstract
In this work hydrothermal synthesis of zeolite NaA crystals with a composition of Al2O3:aSiO2:bNa2O:cH2O was investigated. Effects of SiO2/Al2O3, Na2O/Al2O3 and H2O/Al2O3 ratios and crystallization temperature and time were studied on crystallinity and crystal size of zeolite NaA crystals. It was tried to understand the interactions between these parameters. The crystal species of zeolite NaA were characterized by XRD and SEM.
Considering the interactions between these parameters showed that effects of increasing SiO2/Al2O3 and Na2O/Al2O3 ratios simultaneously neutralize each other so that their overall effect is not significant. On the other hand, the effects of increasing SiO2/Al2O3 and H2O/Al2O3 ratios reinforce each other and significantly affect crystallinity and crystal size. Increasing alkalinity increases crystallization rate and reduces synthesis time. Also, effects of increasing crystallization temperature and time simultaneously reinforce the effects of each other.
The effect of decreasing alkalinity is moderated with that of increasing Na+ content in the synthesis gel.

Abstract In this study, ZIF-67 was synthesized through solvothermal method to remove Cr(VI) ions from aqueous solution. To improve the structural properties of ZIF-67 and its adsorption capacity, optimization of the synthesis conditions was carried out based on maximum Cr(VI) uptake. From experiments, the optimum condition was revealed as solvent: metal ion molar ratio of 4.6:1, ligand: metal ion molar ratio of 318:1 and temperature of 23℃. The physio-chemical properties of as-synthesized ZIF-67 were investigated by BET, XRD, FTIR and FESEM analyses. Effect of adsorption pH, adsorbent dosage, initial concentration and contact time on adsorption process was investigated. Based on the results, the maximum adsorption capacity of Cr(VI) was 26.27 mg/g which was obtained at 35℃, pH= 5, adsorbent dosage of 3 g/l and initial concentration of 107.82 mg/l. The equilibrium time for Cr(VI) adsorption varied from 180 min for low initial concentration of 9 mg/L to 240 min for a high initial concentration of 90 mg/L. For the synthesized ZIF-67, maximum uptake capacity was reported 26.27 mg/g at initial concentration of 107.82 mg/l. The equilibrium data were described better by Langmuir-Freundlich isotherm model than the other models at three different temperatures. Pseudo-second-order model fitted the experimental data better than pseudo-first-order one. Adsorption thermodynamics indicated that the adsorption process was endothermic and spontaneous in nature. The regenerability of ZIF-67 was also studied in three sequential cycles and the Cr(VI) adsorption was almost retained after two cycles.

Abstract The effect of temperature (25, 40, 55 and 70°C) and weight fraction of MWCNTs (0.125, 0.25 and 0.5 %wt) on the viscosity of nanofluids containing pristine and functionalized MWCNTs have been investigated. For this purpose, all of the measurements were carried out in triplicate and were analyzed using two factors completely randomized design and comparison of data means is carried out with Duncan’s multiple range test. The level of statistical significance was determined at 95%. The experimental and statistical results show that the viscosity of the both nanofluids increases with respect to the weight fraction and by decreasing the temperature. Statistical analysis of viscosity shows that temperature, weight fraction and interaction effect of them have a significant influence on the viscosity of nanofluids containing pristine and functionalized MWCNTs (α=0.05). Meanwhile, the results show that there was a significant difference at different levels of temperature on the viscosity of the both nanofluid.

Abstract The redox behavior cobalt chloride was studied voltammetrically in presence and absence of L- Carrageenan (LK) natural polymer using glassy carbon electrodes in 0.1 M KCl supporting electrode. Scan rates are studied for the redox behaviors for CoCl2 alone or in presence of L- Carrageenan (LK) natural polymer. Stability constants for the interaction of cobalt ions with L - Carageenan (LK) natural polymer are evaluated. All mechanisms are discussed.The redox behavior cobalt chloride was studied voltammetrically in presence and absence of L- Carrageenan (LK) natural polymer using glassy carbon electrodes in 0.1 M KCl supporting electrode. The interaction of CoCl2 with L-Carrageenan (LK) has been studied using cyclic voltammetry technique in the potential range (+1.5 to -1.0) V at different scan rates in water at 292.15 oK using KCl (0.1M) as supporting medium and glassy carbon as a working electrode. The study is valuable for evaluating the thermodynamic properties [3-18]. The cobalt ions used show two oxidation peak at 0.02 and 0.06 V and two reduction peaks at 0 and -0.7 V These two peaks corresponding to the oxidation of cobalt zero valent to monovalent and then the oxidation of cobalt monovalent to divalent cobalt Scan rates are studied for the redox behaviors for CoCl2 alone or in presence of L- Carrageenan (LK) natural polymer. Stability constants for the interaction of cobalt ions with L - Carageenan (LK) natural polymer are evaluated. All mechanisms are discussed.

Abstract Due to the importance of nanoparticles stability in industrial applications, in this research, stability of laponite nanoparticles dispersions containing different concentrations of sodium sulfonated polyacrylamide (SPA) was investigated in electrolyte media for oil reservoirs applications. In this regard, effect of parameters such as polymer concentration, temperature, and ionic strength were studied via different methods such as Fourier transform infrared (FT-IR) spectroscopy, dynamic light scattering (DLS) and zeta potential. In FT-IR spectra of SPA-laponite dispersion, in addition to typical peaks of laponite, there was a weak peak at 1040cm-1 characterizing SPA polymer. The z-average particle sizes of laponite particles increased after 168 h of aging in presence of SPA polymer. Zeta potential measurements showed that, adsorption of anionic groups of polymer on particle surface during the aging process has led to a decrease in zeta potential value (toward more negative values). It was seen that dispersion stability depended on polymer concentration, ionic strength of aqueous media, and temperature. Visual observations showed that the stability of laponite nanoparticles in electrolyte media was improved by increasing the SPA polymer concentration. The rheological studies showed that the viscosity curves of SPA-laponite dispersions were located below those of the corresponding pure SPA polymer solutions. Consequently, particle settling was hindered by increasing the polymeric matrix viscosity. Furthermore, using a power-law equation fitted to the polymer solution viscosity-shear rate data, it was shown that laponite nanoparticles stability in electrolyte media could be improved by decreasing the power-law coefficient.

Abstract This study introduces an experimental and theoretical investigation of the performance of a proposed air dehumidification system using a nanofluid of γ-alumina nano-particles in LiBr/H2O as a desiccant. Comparative experiments organized using a central composite design were carried out to evaluate the effects of six numerical factors (air velocity, desiccant flow rate, air humidity ratio, desiccant solution concentration, air temperature, desiccant temperature) and one categorical factor (adding nano-particles) on outlet air humidity ratio and outlet air temperature as responses. Reduced quadratic models were derived for each response. The results revealed that the concentration of LiBr/H2O solution and air temperature had the largest effect on outlet air humidity ratio and outlet air temperature, respectively. It was found that the average increase in mass transfer rate was 12.23% and heat transfer rate was 13.22% when γ-alumina nano-particles (0.02% wt) were added to the LiBr/H2O solution. The average increase in mass transfer coefficient was 22.73% and heat transfer coefficient was 26.51%.

Abstract In this paper, xCuO/CeO2–γAl2O3 nano-catalysts were successfully synthesized by precipitation from an aqueous solution which modified via ultrasonic waves. For characterization of xCuO/CeO2–γAl2O3 samples N2 adsorption results showed that the BET surface area of the CuO/CeO2–γAl2O3, X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-rays (EDX dot-mapping) were used. The BET, XRD and SEM results indicate that CuO/CeO2-γAl2O3 particles are nano-structured catalysts. These catalysts (xCuO/CeO2–γAl2O3) have high specific surface area and finer particle that confirm SEM pictures. xCuO/CeO2-γAl2O3 catalysts compared to other previous synthesised catalysts for selective CO oxidation. The activity and selectivity of these catalysts obtained in the presence of rich hydrogen stream, with space velocity of 30,000 h−1 in the absence of CO2 and H2O. Results show that CuO/CeO2–γAl2O3 catalyst represents high CO conversion in low temperature (less than 120 ◦C), and selectivity of more than 63% at 100 ◦C. Also, results show that decreasing of CeO2 amount decreases selectivity of CO oxidation.

Abstract A high performance activated carbon was synthesized using walnut shell as a solid waste through a two-step zinc chloride chemical activation-thermal pyrolysis process. Characterization results demonstrated its porous structure with very good textural properties such as high BET surface area (1223 m2/g) and high total pore volume (0.85 cm3/g). The final adsorbent was used for adsorption of Fe (II) and Cr (VI) from aqueous solution. Effect ofpH, initial concentration of metal ions, temperature, and contact time on adsorption capacity of the adsorbent was investigated. Adsorption results revealed that the maximum removal of Fe (II) and Cr (VI) ions, occurred at pH 4. 5 and 2 respectively, were 96.2% and 99% at 313K. The equilibrium and kinetics data for adsorption of single-component ions were well described by the Sips isotherm and the pseudo-nth-order models, respectively. The impact of competing ions was studied by adsorption of a binary solution of Fe (II) and Cr (VI) ions. The binary adsorption isotherm was described by the modified Langmuir model and model parameters were found following an optimization procedure by genetic algorithm. Finally, the developed walnut-shell based activated carbon showed higher adsorption efficiency compared to other activated carbons at similar conditions.

Abstract After fullerene and nanotubes, graphene is a new allotrope of carbon. This attractive nanomaterial can be produced by different methods. In this work, we have used the less common approach for preparation of graphene. This technique is based on the utilization of supercritical fluid. Ethanol was used as the solvent for exfoliation of pristine graphite, at the temperature of 400 oC and pressure of 40 MPa. In addition, supercritical ethanol was used to reduce and exfoliate graphite oxide. FT-IR spectra indicate that reduction and exfoliation of graphite oxide can be done in supercritical ethanol, simultaneously. Effect of graphite oxidation on the yield and quality of graphene was investigated and results showed that oxidation of graphite can improve the yield of supercritical process from 12.5% to 26.8%, but Raman spectra revealed that quality of graphene samples produced by graphite oxide is lower than neat graphite. Moreover, the impacts of initial graphite concentration and sonication power on the exfoliation yield were studied. Finally, hybrid structure of graphene and titanium dioxide nanoparticles were prepared by ultrasonic method and used for photocatalytic degradation of methylene blue dye pollutant. Results revealed that titanium dioxide nanoparticles show better photocatalytic performance in presence of graphene sheets.

Abstract The aim of the current research is concentrated on the synthesis of the different nanoparticles such as SnO2 and ZnO nanoparticles and SnO2-ZnO hybrid via sol gel method to investigate their photocatalytic applications for removal of methyl orange pollutant in water. Therefore, ZnCl2 and SnCl2.2H2O were used as ZnO and SnO2 source respectively. The samples were characterized by X-ray diffraction (XRD) spectroscopy, Fourier transform infrared spectroscopy (FTIR) and UV-Vis spectroscopy. XRD results revealed that the crystalline structure of SnO2 and ZnO nanoparticles were formed. FTIR analysis confirmed the presence of ZnO and SnO2 nanoparticles. Optical properties of samples measured using UV-Vis spectrophotometer and the achieved results demonstrated that the photocatalytic activity ofSnO2-ZnO hybrid for the degradation of methyl orange is higher than that of SnO2 nanoparticles and lower than that of ZnO nanoparticles. Weight fraction dependence study also showed that the degradation of methyl orange dye increases with weight fraction. The experimental results revealed that after 35 min UV light irradiation, the photocatalytic degradation of MO using 0.5 g ZnO, hybrid of ZnOSnO2 and SnO2 nanoparticles reached to 99.35%, 92.14% and 87.91%, respectively. In addition, maximum removal efficiency of MO was related to the suspension containing of 0.5 g of ZnO hybrid equal to 99.35%.

Abstract In this paper, we report for the first time, thermal conductivity behavior of nanofluids containing decorated MWCNTs with different amount of TiO2 nanoparticles. TEM image confirmed that the outer surface of MWCNTs successfully decorated with TiO2 nanoparticles. The results of thermal conductivity behavior of nanofluids revealed that the thermal conductivity and enhancement ratio of thermal conductivity of MWCNTsTiO2 at different amount of TiO2 nanoparticles are higher than those of TiO2 and MWCNTs nanofluids. Temperature and weight fraction dependence study also shows that the thermal conductivity of all nanofluids increases with temperature and weight fraction. However, the influence of temperature is more significant than that of weight fraction. We also found that decreasing amount ofTiO2 nanoparticles which introduce the outer surface of MWCNTs leads to the augmentation of thermal conductivity of nanofluids containing MWCNTs-TiO2.

Abstract Coal is widely used in activated carbon production as an important precursor. Product properties of the coal gasification are as functions of coal type and operating conditions, so processing of any coal to produce activated carbon follows a different approach. In this study, a coal sample from Goltoot mine, one of the important coal mines in Iran was selected. Pre-oxidation, charring and activation of the coal were carried out in a rotary kiln reactor at different operating conditions. The results showed excellent potential of the coal for producing high quality activated carbon with controllable pore structure. Steam activation of the char at temperature 860 °C for 3 hr produced an activated carbon with surface area around 1300 m2/gr and yield %20 wt.
The effects of operating conditions such as activation time and temperature and
reactant gas type were studied to develop the tailored properties in the product.