Ethylbenzene Removal by Carbon Nanotubes from Aqueous Solution

The removal of ethylbenzene (E) from aqueous solution by multiwalled, single-walled, and hybrid carbon nanotubes (MWCNTs, SWCNTs, and HCNTs) was evaluated for a nanomaterial dose of 1 g/L, concentration of 10–100 mg/L, and pH 7. The equilibrium amount removed by SWCNTs (E: 9.98 mg/g) was higher than by MWCNTs and HCNTs. Ethylbenzene has a higher adsorption tendency on CNTs, so that more than 98% of it adsorbed in first 14 min, which is related to the low water solubility and the high molecular weight. The SWCNTs performed better for ethylbenzene sorption than the HCNTs and MWCNTs. Isotherms study indicates that the BET isotherm expression provides the best fit for ethylbenzene sorption by SWCNTs. Carbon nanotubes, specially SWCNTs, are efficient and rapid adsorbents for ethylbenzene which possess good potential applications to maintain high-quality water. Therefore, it could be used for cleaning up environmental pollution to prevent ethylbenzene borne diseases

A RIGOROUS COMPARISON OF METHODS FOR MULTI-WALLED CARBON NANOTUBES PURIFICATION USING RAMAN SPECTROSCOPY

Multi-walled carbon nanotubes (MWNT’s) were synthesized using chemical vapor deposition (CVD) method in a fluidized bed reactor under the flow of methane and hydrogen gases. A Cobalt-molybdenum/magnesium oxide (Co-Mo/MgO) nanocatalyst was used as the catalyst of the process. The samples were analyzed using scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses. The effects of different combinations of purification methods, including oxidation, HCl treatment, and HNO3 treatment and the sequence of performing these methods on the quality of the carbon nanotubes are discussed. Raman spectroscopy with a laser excitation of 532 nm was utilized as the measurement tool. The results provide the best purification methods of synthesized carbon nanotubes. The IG/ID ratio for the optimum sample is equal to 1.28. Moreover, as another application of Raman analysis results, the apparent Young’s modulus of MWNT’s was calculated by the use of intensity ratio ID/IG. As expected, the optimum sample had the highest apparent Young’s modulus of 40459.85 MPa.</span

Iranian EFL Learners’ Motivation Construction: Integrative Motivation Revisited

Although Gardner and his associates’ work was most influential in the field of L2 motivation, from the early 1990s onwards, their work has been criticized for several reasons. Some researchers claimed that integrative and instrumental orientations were no longer able to convey the complexity of the L2 motivation construct. To examine this complexity, the present study attempted to investigate the discursive construction of four (two males and two females) Iranian EFL learners’ motivation at Shiraz University, Iran. Employing van Leeuwen’s (2008) legitimation construction framework, the study revealed that depending on their future selves, each participant employed certain discursive strategies unique to him/her to (de)legitimize his/her future self. Therefore, what was observed was the use of strategies which were idiosyncratic to that particular person, in that particular context, for a specific purpose, and for that particular moment. Additionally, given the unique political conditions of Iran in the world, it was found that integrative and instrumental orientations can be best replaced by ideal and ought-to selves in this context. The study has some implications. Motivation researchers need to broaden the unit of analysis beyond the individual learner to the interaction between the individual and the multitude of factors in diverse social settings

Continuous adsorption of natural organic matters in a column packed with carbon nanotubes

In the present study, continuous adsorption experiments were carried out in an adsorption column to survey the efficiency of the carbon nanotubes (CNTs) for removal of natural organic matters (NOMs) from aqueous solution. Parameters such as mass of CNTs, initial NOMs concentration were evaluated and also the breakthrough curves were obtained. Experiments performed with various initial NOMs concentration and various CNTs masses. The breakthrough period was longer at lower initial NOMs concentration. Increase of the initial NOMs concentration, expectedly, resulted in the faster saturation of the CNTs bed. The adsorption capacities for multi wall carbon nanotubes (MWCNT) and single wall carbon nanotubes (SWCNT) in highest initial NOMs concentration were 53.46 and 66.24 mg/g, respectively. The effect of amount of CNTs on breakthrough time and volume of treated water was investigated and resulted that with an increase in the mass of CNTs, breakthrough time occurs very late and the volume of treated water increased. These findings suggested that CNTs present a great potential in removal of NOMs from aqueous solutions

Predicting the Impact of Multiwalled Carbon Nanotubes on the Cement Hydration Products and Durability of Cementitious Matrix Using Artificial Neural Network Modeling Technique

In this study the feasibility of using the artificial neural networks modeling in predicting the effect of MWCNT on amount of cement hydration products and improving the quality of cement hydration products microstructures of cement paste was investigated. To determine the amount of cement hydration products thermogravimetric analysis was used. Two critical parameters of TGA test are PHPloss and CHloss. In order to model the TGA test results, the ANN modeling was performed on these parameters separately. In this study, 60% of data are used for model calibration and the remaining 40% are used for model verification. Based on the highest efficiency coefficient and the lowest root mean square error, the best ANN model was chosen. The results of TGA test implied that the cement hydration is enhanced in the presence of the optimum percentage (0.3 wt%) of MWCNT. Moreover, since the efficiency coefficient of the modeling results of CH and PHP loss in both the calibration and verification stages was more than 0.96, it was concluded that the ANN could be used as an accurate tool for modeling the TGA results. Another finding of this study was that the ANN prediction in higher ages was more precise

Ultra-stable nanofluid containing Functionalized-Carbon Dots for heat transfer enhancement in Water/Ethylene glycol systems: Experimental and DFT studies

A facile hydrothermal method was applied to synthesize functionalized-carbon dot nanoparticles. The analysis revealed a low crystallinity with amorphous nature for particles with a size below 17 nm, which were functionalized with oxygen (17.9%) and nitrogen (12.2%). A nanofluid was formed by dispersing the nanoparticles in a mixture of water and ethylene glycol. The zeta potential measurement confirmed the stability of the nanofluid (-61.5 mV). Viscosity and density measurements revealed that the suspended nanoparticles did not noticeably increase the viscosity (maximum 8%) and density (maximum 1.2%). The thermal conductivity increased as temperature and nanoparticle concentration increased, and a maximum enhancement of 21% was obtained at 45 °C and 0.5 Wt%. Then, the convection heat transfer was investigated in the turbulent regime. The results showed a remarkable enhancement of the convective heat transfer coefficient (34%) at the Reynolds number of 15529 and 0.5 Wt%. Finally, the density functional theory (DFT) method was applied to interpret the long-term stability of the nanofluid. These results showed that the surface functional groups play a prominent role in the stability of the nanofluids. The calculations indicate that the bonding between the functionalized nanoparticles and the solvent fluid occurs through hydrogen bonds and electrostatic dipolar interactions

A PARAMETRIC STUDY ON THE GROWTH OF SINGLE-WALLED CARBON NANOTUBES OVER CO-MO/MGO NANOCATALYST IN A FLUIDIZED BED REACTOR BY CCVD METHOD

Single-walled carbon nanotubes (SWNTs) with high yield and quality were synthesized using chemical vapor deposition (CVD) over Co-Mo/ MgO nanocatalyst in a fluidized bed reactor. Different parameters such as temperature, the ratio of hydrocarbon source to hydrogen, the flow rate of gas, growth time, the size of catalyst particles, heating rate, and the kind of hydrocarbon source were examined to assess their effects on the SWNT synthesis. The influence of these parameters on the carbon nanotubes yield and quality is also reported. Single-walled carbon nanotubes were characterized by using different characterization techniques including thermo-gravimetric analysis (TGA), scanning electron microscopy (SEM), tunneling electron microscopy (TEM), Raman spectroscopy, and X-ray diffraction (XRD). Under the optimum operation conditions (900 °C, 30 min, rate of gas=1800 ml/min, heating rate of 7 °C/min, size of catalyst particle=212 μm, volumetric ratio of hydrocarbon source to hydrogen=1:1), single-walled carbon nanotubes with an average diameter of 0.9 nm and a yield of 300% (related to the catalyst) were produced. </span

Predicting the Impact of Multiwalled Carbon Nanotubes on the Cement Hydration Products and Durability of Cementitious Matrix Using Artificial Neural Network Modeling Technique

In this study the feasibility of using the artificial neural networks modeling in predicting the effect of MWCNT on amount of cement hydration products and improving the quality of cement hydration products microstructures of cement paste was investigated. To determine the amount of cement hydration products thermogravimetric analysis was used. Two critical parameters of TGA test are PHP loss and CH loss . In order to model the TGA test results, the ANN modeling was performed on these parameters separately. In this study, 60% of data are used for model calibration and the remaining 40% are used for model verification. Based on the highest efficiency coefficient and the lowest root mean square error, the best ANN model was chosen. The results of TGA test implied that the cement hydration is enhanced in the presence of the optimum percentage (0.3 wt%) of MWCNT. Moreover, since the efficiency coefficient of the modeling results of CH and PHP loss in both the calibration and verification stages was more than 0.96, it was concluded that the ANN could be used as an accurate tool for modeling the TGA results. Another finding of this study was that the ANN prediction in higher ages was more precise

Potential of Acid-Activated Bentonite and SO3H-Functionalized MWCNTs for Biodiesel Production From Residual Olive Oil Under Biorefinery Scheme

Application of acid-activated bentonite and SO3H-functionlized multiwall carbon nanotubes (SO3H-MWCNTs) for lowering free fatty acids (FFAs) content of low-quality residual olive oil, prior to alkali-catalyzed transesterification was investigated. The used bentonite was first characterized by Scanning Electron Microscopy (SEM), Inductively Coupled Plasma mass spectrometry (ICP-MS), and X-ray fluorescence (XRF), and was subsequently activated by different concentrations of H2SO4 (3, 5, and 10 N). Specific surface area of the original bentonite was measured by Brunauer, Emmett, and Teller (BET) method at 45 m2/g and was best improved after 5 N-acid activation (95–98°C, 2 h) reaching 68 m2/g. MWCNTs was synthesized through methane decomposition (Co-Mo/MgO catalyst, 900°C) during the chemical vapor deposition (CVD) process. After two acid-purification (HCl, HNO3) and two deionized-water-neutralization steps, SO3H was grafted on MWCNTs (concentrated H2SO4, 110°C for 3 h) and again neutralized with deionized water and then dried. The synthesized SO3H-MWCNTs were analyzed using Fourier-Transform Infrared Spectroscopy (FTIR) and Transmission Electron Microscopy (TEM). The activated bentonite and SO3H-MWCNTs were utilized (5 wt.% and 3 wt.%, respectively), as solid catalysts in esterification reaction (62°C, 450 rpm; 15:1 and 12:1 methanol-to-oil molar ratio, 27 h and 8 h, respectively), to convert FFAs to their corresponding methyl esters. The results obtained revealed an FFA to methyl ester conversion of about 67% for the activated bentonite and 65% for the SO3H-MWCNTs. More specifically, the acid value of the residual olive oil was decreased significantly from 2.5 to 0.85 and 0.89 mg KOH/g using activated bentonite and SO3H-MWCNTs, respectively. The total FFAs in the residual olive oil after esterification was below 0.5%, which was appropriate for efficient alkaline-transesterification reaction. Both catalysts can effectively pretreat low-quality oil feedstock for sustainable biodiesel production under a biorefinery scheme. Overall, the acid-activate bentonite was found more convenient, cost-effective, and environment-friendly than the SO3H-MWCNTs

Evaluation of clustering role versus Brownian motion effect on the heat conduction in nanofluids: A novel approach

In this study, the temperature and viscosity-dependent methods were used to identify the main heat conduction mechanism in nanofluids. Three sets of experiments were conducted to investigate the effects of Brownian motion and aggregation. Image processing approach was used to identify detailed configurations of different nanofluids microstructures. The thermal conductivity of the nanofluids was measured with respect to the dynamic viscosity in the temperature range between 0 and 55 °C. The results clearly indicated that the nanoparticle Brownian motion did not play a significant role in heat conduction of nanofluids, which was also supported by the observation that a more viscous sample rendered a higher thermal conductivity. Moreover, the microscopic pictures and the differences in the viscosity between theoretical and experimental values suggested the major role of particle aggregation and clustering