Effect of reaction time and catalyst feed rate towards carbon nanotubes yields and purity by using rotary reactor

Continuous production of multi-walled carbon nanotubes (MWCNTs) by chemical vapor deposition (CVD) method was investigated in a rotary reactor. The aim of the study was to investigate the effect of catalyst feeding rate and reaction time on the MWCNTs production yield and purity. Bimetallic Co-Mo supported on MgO was used for the growth of MWCNTs and methane gas was used as the carbon precursor. The results indicated that the highest yield of MWCNTs production was attained at the reaction time of 180 min and catalyst feeding rate of 100 mg/min; this sample also had the highest purity (99.16%). SEM and TEM analyses of the synthesized product confirmed that most of the MWCNTs were sinuous and entangled with a uniform diameter. Raman spectroscopy indicated that the as-produced MWCNTs were mostly graphitic with few disordered carbon and impurities. The results highlighted that synthesized MWCNTs were highly pure which eliminates the need for MWCNTs purification process

Graphène chimiquement modifié et auto-assemblé comme adsorbant pour des applications en environnement

Ideal or pristine graphene is a single atom-thick layer of sp² hybridized carbon atoms. Besides, graphene can also be seen in other forms as graphene derivatives, including graphene oxide (GO) and reduced graphene oxide (rGO). Our study demonstrated that GO is suitable to be used as starting material and can also be chemically and physically activated to be used as an adsorbent for CO₂ capture. In addition, three-dimensional (3D) graphene materials have recently gained a great deal of interest due to their ability to preserve the intrinsic properties of 2D graphene sheets while providing advanced functions that improve performance in a wide range of applications, especially, environmental remediation. Thus, the next section of this study describes the process of developing 3D graphene based monoliths (GBMs) and chemically modified the prepared porous 3D GBMs by using atomic layer deposition (ALD) of alumina (Al₂O₃), which offers advantages such as precursor diffusion, no contamination, phase control, and the ability to deposit nanoparticles or nanofilms. Further, to better understand the characteristics of the developed materials, some standard and advanced characterization techniques (e.g.; TEM/STEM/EELS on thin lamellas prepared by FIB) have been selected to study the surface chemistry and structural properties of the chemically modified 3D GBM hybrids. Lastly, the 3D Al₂O₃ / GBM hybrid developed by ALD was tested for Congo red dye adsorption, and it showed increased adsorption capacity than pristine 3D GBMs, owing to the favourable interactions between the alumina surface and Congo red.Le graphène idéal est une couche d'épaisseur atomique composé exclusivement d'atomes de carbone hybridés sp². En outre, le graphène peut également être vu sous d'autres formes dites dérivés du graphène, y compris l'oxyde de graphène (GO) et l'oxyde de graphène réduit (rGO). Notre étude a démontré que le GO peut être utilisé comme matériau de départ et être activé chimiquement et physiquement pour être utilisé comme adsorbant pour la capture du CO₂. De plus, des matériaux à base de graphène tridimensionnels (3D) ont récemment suscité beaucoup d'intérêt en raison de leur capacité à préserver les propriétés intrinsèques des feuilles de graphène 2D tout en offrant des fonctions avancées qui améliorent les performances dans un large champ d'applications, en particulier la dépollution. Ainsi, la section suivante de cette étude décrit le processus de développement de monolithes à base de graphène 3D (GBM) et la modification chimique des GBM 3D poreux préparés en utilisant un dépôt par Atomic Layer Deposition (ALD) d'alumine (Al₂O₃). L’ALD offre des avantages tels que la bonne diffusion des précurseurs au sein des porosités, l’absence de contamination, le contrôle de phase déposée et la possibilité de déposer des nanoparticules ou des nanofilms selon l’interaction des précurseurs avec la surface à couvrir. De plus, pour mieux comprendre les caractéristiques des matériaux développés, des techniques de caractérisation standards couplées avec des approches technologiques avancées (par exemple ; TEM/STEM/EELS sur des lamelles minces préparées par FIB) ont été mises en oeuvre pour étudier la chimie de surface et les propriétés structurelles des GBM 3D chimiquement modifiés. Enfin, l'hybride 3D Al₂O₃ / GBM développé par ALD a été testé pour l'adsorption du colorant rouge Congo, et il a montré une capacité d'adsorption accrue par rapport aux GBM 3D vierges, en raison des interactions favorables entre la surface d'alumine et le rouge Congo

Chemical Surface Modification Of Graphene Nanoplatelets By Carboxylation Process For Enhanced Sorption Capacities

The aim of this thesis is to investigate the surface modification of carbon through chemical or physical attachment via carboxylation process for environmental remediation applications such as dye removal from wastewater. Chemical functionalization of graphene is required in many environmental applications and proper functionalization is an efficient approach to improve the adsorption capacity of graphene. Functionalized graphene nanoplatelet (fGNP) is a promising material for dye removal as this all-carbon nanomaterial possesses high specific surface area and has the ability to create a strong electrostatic interaction with a variety of oxygen-containing functional groups and π-electron systems. The effect of fGNP has not been widely explored, and many research groups worldwide have been focusing only on CNT, graphene, GO and rGO surfaces. In this thesis, a facile approach for the surface modification and fGNP were investigated. The approach involves fGNP with different type of acid and volumetric ratio acid to prove the best condition for greater dispersibility. Two type of acid used in this approach which are sulphuric acid and nitric acid. Their facile chemically modification by acid oxidation induces both facile dispersion in water and high adsorption capacity of methylene blue. Morphological, structural and chemical properties of the fGNP are deeply investigated by a set of complementary characterization techniques such as Fourier transformed infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), High-resolution transmission electron microscopy (HRTEM), Thermogravimetric analysis (TGA) , Raman Spectroscopy and Zeta potential measurement. The BET surface areas raw GNP and functionalize GNP were in the range of 115-150 m2/g. Effects of temperature (30-60 °C), contact time (5 to 55 min), and initial dye concentration (25-200 mg/L) on adsorption performance of adsorbents were investigated. The maximum adsorption capacity of fGNPs increased from 112 mg/g to 151 mg/g at pH 4 and 60 °C. This can be directly linked to the increased of functional groups such as hydroxyl and carboxyl on the surface of modified adsorbents resulting in higher adsorption performance of fGNP. The equilibrium data gained were evaluated using isotherms, kinetic adsorption models and thermodynamic studies. For fGNP1 adsorbents, the isotherm data were significantly described by Langmuir model. The kinetic study revealed that the pseudo-first-order rate model was in better agreement with the experimental data. The values of the thermodynamic parameters, including ΔG0 (9.39,9.21 and 9.45 for temperature 30°C., 45°C, and 60 °C respectively), ΔH0 (8.85 kJ/mol) and ΔS0 (−1.57 kJ/mol). From the results, fGNP showed that MB adsorption is a spontaneous and endothermic process

Chemically modified graphene as nano-adsorbent for environmental applications

Le graphène idéal est une couche d'épaisseur atomique composé exclusivement d'atomes de carbone hybridés sp². En outre, le graphène peut également être vu sous d'autres formes dites dérivés du graphène, y compris l'oxyde de graphène (GO) et l'oxyde de graphène réduit (rGO). Notre étude a démontré que le GO peut être utilisé comme matériau de départ et être activé chimiquement et physiquement pour être utilisé comme adsorbant pour la capture du CO₂. De plus, des matériaux à base de graphène tridimensionnels (3D) ont récemment suscité beaucoup d'intérêt en raison de leur capacité à préserver les propriétés intrinsèques des feuilles de graphène 2D tout en offrant des fonctions avancées qui améliorent les performances dans un large champ d'applications, en particulier la dépollution. Ainsi, la section suivante de cette étude décrit le processus de développement de monolithes à base de graphène 3D (GBM) et la modification chimique des GBM 3D poreux préparés en utilisant un dépôt par Atomic Layer Deposition (ALD) d'alumine (Al₂O₃). L’ALD offre des avantages tels que la bonne diffusion des précurseurs au sein des porosités, l’absence de contamination, le contrôle de phase déposée et la possibilité de déposer des nanoparticules ou des nanofilms selon l’interaction des précurseurs avec la surface à couvrir. De plus, pour mieux comprendre les caractéristiques des matériaux développés, des techniques de caractérisation standards couplées avec des approches technologiques avancées (par exemple ; TEM/STEM/EELS sur des lamelles minces préparées par FIB) ont été mises en oeuvre pour étudier la chimie de surface et les propriétés structurelles des GBM 3D chimiquement modifiés. Enfin, l'hybride 3D Al₂O₃ / GBM développé par ALD a été testé pour l'adsorption du colorant rouge Congo, et il a montré une capacité d'adsorption accrue par rapport aux GBM 3D vierges, en raison des interactions favorables entre la surface d'alumine et le rouge Congo.Ideal or pristine graphene is a single atom-thick layer of sp² hybridized carbon atoms. Besides, graphene can also be seen in other forms as graphene derivatives, including graphene oxide (GO) and reduced graphene oxide (rGO). Our study demonstrated that GO is suitable to be used as starting material and can also be chemically and physically activated to be used as an adsorbent for CO₂ capture. In addition, three-dimensional (3D) graphene materials have recently gained a great deal of interest due to their ability to preserve the intrinsic properties of 2D graphene sheets while providing advanced functions that improve performance in a wide range of applications, especially, environmental remediation. Thus, the next section of this study describes the process of developing 3D graphene based monoliths (GBMs) and chemically modified the prepared porous 3D GBMs by using atomic layer deposition (ALD) of alumina (Al₂O₃), which offers advantages such as precursor diffusion, no contamination, phase control, and the ability to deposit nanoparticles or nanofilms. Further, to better understand the characteristics of the developed materials, some standard and advanced characterization techniques (e.g.; TEM/STEM/EELS on thin lamellas prepared by FIB) have been selected to study the surface chemistry and structural properties of the chemically modified 3D GBM hybrids. Lastly, the 3D Al₂O₃ / GBM hybrid developed by ALD was tested for Congo red dye adsorption, and it showed increased adsorption capacity than pristine 3D GBMs, owing to the favourable interactions between the alumina surface and Congo red

Physical and Chemical Activation of Graphene-Derived Porous Nanomaterials for Post-Combustion Carbon Dioxide Capture

Activation is commonly used to improve the surface and porosity of different kinds of carbon nanomaterials: activated carbon, carbon nanotubes, graphene, and carbon black. In this study, both physical and chemical activations are applied to graphene oxide by using CO2 and KOH-based approaches, respectively. The structural and the chemical properties of the prepared activated graphene are deeply characterized by means of scanning electron microscopy, Raman spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectrometry and nitrogen adsorption. Temperature activation is shown to be a key parameter leading to enhanced CO2 adsorption capacity of the graphene oxide-based materials. The specific surface area is increased from 219.3 m2 g−1 for starting graphene oxide to 762.5 and 1060.5 m2 g−1 after physical and chemical activation, respectively. The performance of CO2 adsorption is gradually enhanced with the activation temperature for both approaches: for the best performances of a factor of 6.5 and 9 for physical and chemical activation, respectively. The measured CO2 capacities are of 27.2 mg g−1 and 38.9 mg g−1 for the physically and chemically activated graphene, respectively, at 25 °C and 1 bar

Chemical Modification of Carbon Nanomaterials and their Potential for Sustainable Technologies

International audienc

Chemical Modification of Carbon Nanomaterials and their Potential for Sustainable Technologies

International audienc