Study of carbon black obtained by pyrolysis of waste scrap tyres

Waste scrap tyres were thermally decomposed under various conditions. Decompositions were followed by the TGA method. Specific heating regimes were tested to obtain optimal structural properties of resulting pyrolytic carbon black produced by pyrolysis of scrap tyres and the process was characterized in temperature interval from 380 to 1,200 °C and heating rate 10, 20 and 50 °C min^?1 under nitrogen atmosphere. The original scrap tyres and pyrolytic carbon black were characterized by Raman and Fourier transform infrared spectroscopy methods. Textural properties were also determined. Effect of temperature and heating rate on process of pyrolysis of scrap tyres was observed. Shifting of temperature of maximum pyrolysis rate to lower value and spreading of DTG peak is caused by increasing heating rate. Temperature 570 °C was sufficient for total scrap tyres pyrolysis. Graphitic and disordered structure was distinguished in the formed carbon black by Raman spectroscopy. With increasing temperature, heating rate and weight loss, the amount of the graphitic structure was reduced at the expense of disordered structure. Destruction of nonporous scrap tyres and formation of porous structure took place at higher temperature. Porous carbon black is formed above 380 °C, specific surface area increased up to 88 m² g^?1 .     

Synthesis of carbon nanotubes using scrap tyre rubber as carbon source

Carbon nanotubes(CNTs) were successfully synthesized through chemical vapor deposition(CVD) method over cobalt catalysts using scrap tyre rubber as carbon source.The CNTs as produced were investigated by means of X-ray diffraction, thermogravimetric analysis,scanning electron microscope,transmission electron microscopy and Raman spectrum techniques.It was found that the obtained carbon material mainly existed in the form of CNTs.     

Preparation and thermal properties of fatty acids/CNTs composite as shape-stabilized phase change materials

A series of fatty acids/carbon nanotubes (CNTs) composite shape-stabilized PCMs were prepared through infiltration method by using the eutectic mixture of capric acid, lauric acid, and palmitic acid as phase change materials, multi-walled CNTs as a supporting material. Nitrogen adsorption–desorption curves and SEM images of composite shape-stabilized PCMs indicate that the eutectic mixture was effectively absorbed into the porous structure of the CNTs. DSC thermograms show that the composite fatty acids/CNTs possess good phase change behavior. And the latent heat of the sample absorbed with 80 wt% fatty acids can achieve 101.6 J g^?1 in the melting process and its phase change temperatures and latent heat almost remain unchanged in 30 times of thermal cycling. Moreover, the thermal conductivity of the composite materials are significantly improved (up to 0.6661 W m^?1 k^?1) due to the addition of the highly thermal conductive CNTs.     

Mesoporous activated carbon from <Emphasis Type="Italic">Pentace</Emphasis> species sawdust via microwave-induced KOH activation: optimization and methylene blue adsorption

This work studied the optimization of preparation conditions of Pentace species sawdust activated carbon (PSAC) via microwave-induced KOH activation for the adsorption of methylene blue (MB) dye from aqueous solutions. The produced activated carbon was characterised through Brunauer–Emmett–Teller (BET) surface area and pore structural analysis, proximate and ultimate, scanning electron microscopy, and Fourier transform infrared spectroscopy. Response surface methodology technique was used to optimize the radiation power, radiation time and impregnation ratio for MB removal and PSAC yield through central composite design. The optimum preparation conditions for PSAC were obtained at a radiation power of 418 W, radiation time of 6.4 min, and an impregnation ratio of 0.5, which resulted in 27% PSAC yield and 93.74% MB removal. A mesoporous structure of PSAC was formed, with a BET surface area, total pore volume and average pore diameter of 914.15 m²/g, 0.52 cm³/g, and 3.19 nm, respectively. The experimental kinetic data were well described by a pseudo-second-order model and intraparticle diffusion. Adsorption data fitted the Redlich–Peterson equation better than the Langmuir, Freundlich, Temkin, Dubinin–Radushkevich and Sips equations. However, the exponential value of Redlich–Peterson approached unity, hence, resulting in the original Langmuir equation, with adsorption capacity of 357.14 mg/g. The adsorption performance was effectively preserved even after four consecutive cycles, demonstrating good regeneration ability.     

Characterization and Artificial Neural Networks Modelling of methylene blue adsorption of biochar derived from agricultural residues: Effect of biomass type,pyrolysis temperature,particle size

Biochar has been explored as a sorbent for contaminants, soil amendment and climate change mitigation tool through carbon sequestration. Through the optimization of the pyrolysis process, biochar can be designed with qualities to suit the intended uses. Biochar samples were prepared from four particle sizes (100–2000 µm) of three different feedstocks (oak acorn shells, jift and deseeded carob pods) at different pyrolysis temperatures (300–600 °C). The effect of these combinations on the properties of the produced biochar was studied. Biochar yield decreased with increasing pyrolysis temperature for all particle sizes of the three feedstocks. Ash content, fixed carbon, thermal stability, pH, electrical conductivity (EC), specific surface area (SSA) of biochar increased with increasing pyrolysis temperature. Volatile matter and pH value at the point of zero charge (pH_pzc) of biochar decreased with increasing pyrolysis temperature. Fourier-transform infrared spectroscopy (FTIR) analysis indicated that the surface of the biochar was rich with hydroxyl, phenolic, carbonyl and aliphatic groups. Methylene blue (MB) adsorption capacity was used as an indicator of the quality of the biochar. Artificial neural networks (ANN) model was developed to predict the quality of the biochar based on operational conditions of biochar production (parent biomass type, particle size, pyrolysis temperature). The model successfully predicted the MB adsorption capacity of the biochar. The model is a very useful tool to predict the performance of biochar for water treatment purposes or assessing the general quality of a design biochar for specific application.     

Porous SiOC composites fabricated from preceramic polymers and wood powders for efficient dye adsorption and removal

Porous SiOC composites for efficient treatment of dye wastewater were prepared using polysiloxane preceramic polymer mixed with wood biomass by pyrolysis under Ar atmosphere. The influences of the pyrolysis temperature on the microstructure, pore feature and adsorption behavior were investigated. The composites contain the α-quartz, cristobalite, nanosized β-SiC and free carbon embedded in a SiOC matrix. The composite obtained at 1300 °C presents a high specific surface area up to 463 m²/g. The adsorption capacity is enhanced by increasing pyrolysis temperature. The adsorption for the removal of methylene blue on the composites follows the pseudo second-order kinetics, and the adsorption data can be described by the Langmuir and Freundlich adsorption isotherms very well. The composite at 1300 °C displays a maximum adsorption capacity up to 173.5 mg/g caused by the enhancement of specific surface area and the existence of sp² carbons, resulting in many favorable adsorption sites and strong electrostatic attraction.     

Effect of pH and Temperature on Adsorption of Dimethyl Phthalate on Carbon Nanotubes in Aqueous Phase

Adsorptions of dimethyl phthalate (DMP) on carbon nanotubes (CNTs) in aqueous phase at various pH and temperatures were studied. The increase in pH results in the increase in adsorption coefficient. The adsorption is governed by the π-π electron interaction which is affected by the changes in pH of the medium. The outer diameter of the CNTs greatly influences the adsorption behavior of CNT for DMP. Under the same working temperature, the adsorption capacity of CNTs for DMP is inversely related to the average outer diameter of the CNT: single-walled SWCNT (1.4 nm)>multi-walled MWCNT10 (9.4 nm)>MWCNT30 (27.8 nm)>MWCNT40 (42.7 nm). The larger surface area of CNTs provides many active sites for adsorption of DMP molecules. The Freundlich model can describe well the adsorption isotherms of DMP on CNTs. The thermodynamic parameters of standard free energy, standard enthalpy (ΔH), and standard entropy changes are determined, showing that the adsorption of DMP on CNTs is an endothermic and spontaneous reaction. The ΔH value of 27.8 nm-sized MWCNT (22.69 kJ/mol) is higher than 1.4 nm-sized SWCNT (6.05 kJ/mol), inferring that the adsorption process becomes more endothermic with the increase in the outer diameter of CNTs.     

Thermal degradation and evolved gas analysis of epoxy (DGEBA)/novolac resin blends (ENB) during pyrolysis and combustion

The thermal degradation of epoxy (DGEBA) and phenol formaldehyde (novolac) resins blend was investigated by using thermogravimetric analysis (TGA) coupled with Fourier transform infrared spectroscopy and mass spectroscopy. The results of TGA revealed that the thermal degradation process can be subdivided into four stages: drying the sample, fast and second thermal decomposition, and further cracking process of the polymer. The total mass loss of 89.32 mass% at 950 °C is found during pyrolysis, while the polymer during the combustion almost finished at this temperature. The emissions of carbon dioxide, aliphatic hydrocarbons, carbon monoxide, etc., while aromatic products, are emitted at higher temperature during combustion and pyrolysis. It was observed that the intensities of CO₂, CO, H₂O, etc., were very high when compared with their intensities during pyrolysis, attributed to the oxidation of decomposition product.     

NiO/CNTs derived from metal-organic frameworks as superior anode material for lithium-ion batteries

In this work, porous NiO microspheres interconnected by carbon nanotubes (NiO/CNTs) were successfully fabricated by the pyrolysis of nickel metal-organic framework precursors with CNTs and evaluated as anode materials for lithium-ion batteries (LIBs). The structures, morphologies, and electrochemical performances of the samples were characterized by X-ray diffraction, N₂ adsorption-desorption, field emission scanning electron microscopy, cyclic voltammetry, galvanostatic charge/discharge tests, and electrochemical impedance spectroscopy, respectively. The results show that the introduction of CNTs can improve the lithium-ion storage performance of NiO/CNT composites. Especially, NiO/CNTs-10 exhibits the highest reversible capacity of 812 mAh g^?1 at 100 mA g^?1 after 100 cycles. Even cycled at 2 A g^?1, it still maintains a stable capacity of 502 mAh g^?1 after 300 cycles. The excellent electrochemical performance of NiO/CNT composites should be attributed to the formation of 3D conductive network structure with porous NiO microspheres linked by CNTs, which benefits the electron transfer ability and the buffering of the volume expansion during the cycling process.     

Thermal degradation and evolved gas analysis of N,N′-bis(2 hydroxyethyl) linseed amide (BHLA) during pyrolysis and combustion

The thermal degradation of N,N′-bis(2 hydroxyethyl) linseed amide (BHLA) was investigated by thermogravimetric analysis coupled with Fourier transform infrared spectroscopy and mass spectroscopy (TG–FTIR–MS). Thermogravimetric analysis revealed that the thermal degradation process can be subdivided into three stages: sample drying (<200 °C), main decomposition (200–500 °C), and further cracking (>500 °C) of the polymer. The compound reached almost 800 °C during pyrolysis and combustion. The activation energy at the second step during combustion was slightly higher than that of pyrolysis emissions of carbon dioxide, aliphatic hydrocarbons, carbon monoxide, and hydrogen cyanide, and other gases during combustion and pyrolysis were detected by FTIR and MS spectra. It was observed that the intensities of CO₂, CO, HCN, and H₂O were very high when compared with their intensities during pyrolysis, and this was attributed to the oxidation of the decomposition product.     

Determination of Silver with On-Line Preconcentration Using Dithiozone Chelate and Carbon Nanotubes for Preconcentration with Detection by Flame Atomic Absorption Spectrometry

A novel flow injection system incorporating a micro-column packed with carbon nanotubes (CNTs) as an adsorbent has been applied to the on-line preconcentration of trace silver with detection by flame atomic absorption spectrometry. Silver is first chelated by dithizone (H₂Dz), then retained on the CNTs surface and afterward quantitatively eluted by methanol. Influencing parameters, including the concentration of reaction reagent, enrichment variables, and elution variables were investigated. The adsorption mechanisms of Ag-H₂Dz chelate retained onto the CNTs surface have also been studied. By loading 6.9 mL sample solution, a linear calibration graph is obtained within the range of 3–120 µg L^?1 with R of 0.9996, and a detection limit (3σ) of 0.8 µg L^?1 is achieved, along with a precision of 1.6% R.S.D. at the 30 µg L^?1 level (n = 7). The dynamic sorption capacity of CNTs for silver is 122 mg g^?1. The procedure is demonstrated by measurement of spike recovery in a series of water samples, giving rise to spike recoveries in the range of 96.8–99.7%.     

Preparation of activated carbon from organic fraction of municipal solid wastes by ZnCl2 activation method and use it for elimination of chromium(VI) from aqueous solutions

In this study, the use of the organic fraction of municipal solid waste as an abundant and low-cost raw material for producing activated carbon was investigated. For this purpose, ZnCl₂ was used as a chemical activation agent and the carbonization process took place at 800 °C in N₂ atmosphere. Seven sorbents were prepared by chemical activation (pyrolysis under N₂ atmosphere at temperature of 800 °C after impregnation with ZnCl₂) with different ratios of ZnCl₂. The optimum ratio of organic fraction of municipal solid waste to ZnCl₂ was inspected via methylene blue number and iodine number (ASTM Designation: D4607–94). The results showed that the adsorbent with 60 % ZnCl₂/raw material was the most appropriate one with a satisfactory adsorption capacity, 112.4 mg g^?1 for methylene blue and 134.0 mg g^?1 for iodine. In addition, the structural analysis of this sorbent was performed using FT-IR, BET surface area, SEM–EDX and thermal analysis. Application of this sorbent to remove Cr(VI) from wastewater was studied to find an adsorption capacity of 66.7 mg g^?1. The experimental adsorption equilibrium data were fitted to Langmuir adsorption model with an acceptable adsorption capacity of 66.7 mg g^?1.     

Organophosphorus pesticides detection using acetylcholinesterase biosensor based on gold nanoparticles constructed by electroless plating on vertical nitrogen-doped single-walled carbon nanotubes

An acetylcholinesterase (AChE) biosensor was constructed based on gold nanoparticles (AuNPs) using electroless plating on vertical nitrogen-doped single-walled carbon nanotubes (VNSWCNTs) for detecting organophosphorus pesticides (OPs). AChE was immobilised on AuNPs via Au–S bonding, and VNSWCNTs were produced by spontaneous chemical adsorption of NSWCNTs on gold electrode, also via Au–S bonding. This modified electrode exhibited excellent electron transfer capacity due to the synergy between AuNPs and VNSWCNTs. The developed biosensor showed good linear relations at concentrations of 10^?5 – 1 ppb, and the detection limits were 3.04 × 10^?6 ppb for methyl parathion, 1.96 × 10^?6 ppb for malathion and 2.06 × 10^?6 ppb for chlorpyrifos, respectively. The AChE biosensor revealed satisfactory stability, excellent sensitivity and good repeatability. These results suggest that this biosensor has good application prospects and can function as a sensitive device in OPs analysis.     

Porous graphene oxide-based carbon artefact with high capacity for methylene blue adsorption

A three-dimensional porous graphene oxide (PGO) material prepared by hydrothermal method was selected to adsorb methylene blue (MB), which demonstrates a high MB adsorption capacity, up to 1100 mg g^?1 in alkaline solution at room temperature. The influences of different pore structures and different contents of oxygen-containing functional groups on MB adsorption behaviors were studied in detail, which indicated that the high MB adsorption capacity is mainly ascribed to the synergistic effect of the large number of oxygen-containing functional groups and the interconnected 3D porous network. Moreover, based on the investigation on the adsorption kinetics and the effect of pH value on MB adsorption, we propose a two-step adsorption kinetics for PGO, which involved in two interactions between MB molecular and porous graphene oxide-based carbon: electrostatic force and π-π stacking. Besides, the calculation of the activation energies indicates that chemisorption dominates the adsorption for PGO in comparison with physisorption for three-dimensional porous graphene materials which has low adsorption capacity because of the removal of functional groups. The results are of great significance for the design and environmental applications of PGO as a promising adsorbent material for water purification.     

Benzene,toluene and o-xylene (BTX) removal from aqueous solutions through adsorptive processes

In this study, the monocomponent adsorption of benzene, toluene and o-xylene (BTX) compounds, as model contaminants present in the petrochemical wastewaters, was investigated using three types of adsorbents: activated carbon (Carbon CD 500), a polymeric resin (MN-202) and a modified clay (Claytone-40). Langmuir and Freundlich models were able to fit well the equilibrium experimental data. The BTX adsorption capacity increased in the following order: Claytone-40 < CD 500 < MN-202. The maximum uptake capacity of MN-202, given by the Langmuir fitting parameter, for benzene, toluene and o-xylene was 0.8 ± 0.1, 0.70 ± 0.08 and 0.63 ± 0.06 mmol/g at 26 °C. Desorption kinetics for polymeric resin with 50 % methanol solution were fast being able to reuse the resin in consecutive adsorption/desorption cycles without loss of sorption capacity. The adsorptive behaviour at batch system was modelled using a mass transfer kinetic model, considering that the sorption rate is controlled by a linear driving force model, which successfully predicts benzene, toluene and o-xylene concentration profiles, with homogeneous diffusivity coefficients, D _h , between 3.8 × 10^?10 and 3.6 × 10^?9 cm²/s. In general, benzene diffuses faster than toluene and o-xylene, which is in agreement with molecular diffusivity in water.     

Observation of curling effects in tubular and planar graphene-like structures by pyrolysis of ferrocene/dichlorobenzene mixtures

In this work, we investigate the morphological and structural properties of carbon nanostructures fabricated by means of chemical vapor deposition (CVD) methods in the presence of controlled quantities of Cl-containing precursor and ferrocene. We report the observation of a structural transition from tubular-like carbon nanotube (CNT) morphology into planar few-layers graphite in experiments involving the pyrolysis of ferrocene and dichlorobenzene mixtures. An unusual intermediate curling-like mechanism in the walls of the as-grown CNTs is found when intermediate quantities of dichlorobenzene are used. This unusual phenomenon vanishes for high quantities of dichlorobenzene, where the nucleation of planar few-layers graphene-like structures directly connected to micrometer-scale Fe₃C particles is found. Such morphological variation is investigated by means of both scanning electron microscopy (SEM) and transmission electron microscopy (TEM), whereas the structural variation of the obtained structures is analyzed through X-ray diffraction and Raman spectroscopy techniques.     

Effect of processing temperature on growing bamboo-like carbon nanotubes by chemical vapor deposition

The present article demonstrates a simple, eco-friendly route for the fabrication of carbon nanotubes (CNTs) with different morphologies, including the fascinating bamboo-like structures without complex catalyst/support preparation procedures. A thermal chemical vapor deposition (CVD) technique that utilized natural pozzolan supports and a solid carbon source, that is, a mixture of camphor and ferrocene in a weight ratio of 20:1, was carried out at different temperatures where the ferrocene played also the role of catalyst. The pozzolan chemical composition and mineral identification were determined by energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy. The morphology of the fabricated CNTs was studied via scanning and transmission electron microscopies (SEM and TEM). It was revealed that both conventional tubular and bamboo-like nanotubes grow at 750 °C while the bamboo-like morphology prevails at 850 °C. The better nanostructure uniformity at higher deposition temperature was accompanied by an improved nanotube graphitization degree that was verified by Raman spectroscopy. Yet, the reduction of the CNTs production yield was recorded by thermogravimetric analysis (TGA). The experimental data are interpreted and discussed as an interplay between the CNTs processing temperature, morphology and growth mechanism. Thus, the growth of either tubular or bamboo-like nanostructures is suggested to be ruled by the competitive surface and bulk diffusions of carbon onto and into the catalyst surface. The growth depends on the size of catalyst nanoparticles sintered at different temperatures. The favorable role of the pozzolan supporting materials in the formation of bamboo-like tubes is emphasized.     

Sorption of Cd(II) onto carbon-based materials—a comparative study

The sorption behaviour of Cd(II) on three carbon-based materials including activated carbon (AC), carbon nanotubes (CNTs) and carbon-encapsulated magnetic nanoparticles (CEMNPs) which were prepared under similar conditions by nitric acid treatment were investigated. Generally, sorption of cadmium on these materials increased with the increase of pH. For AC and CNTs very similar results were obtained, while CEMNPs exhibits much higher affinity for Cd(II) despite of almost the same surface acidity. Thus, cadmium retention on tested sorbents was more dependent on the concentration of specific active sites than the total surface area available. The equilibrium sorption data were better fitted to Langmuir isotherm. The theoretical saturation capacity of the monolayer derived from this model at pH 8.0 for AC, CNTs and CEMNPs are 9.91 mg g^?1, 20.37 mg g^?1 and 91.0 mg g^?1, respectively. The kinetic of Cd(II) sorption is fitted for pseudo-second order equation and could be described as a combination of film diffusion and intra-particle diffusion, whereby the last one dominates. The experimental parameters for preconcentration of cadmium on a microcolumn packed with CEMNPs prior to its determination by flame atomic absorption spectrometry have been investigated. Cadmium can be quantitatively retained at pH 8 from sample volumes up to 150 mL and then eluted completely with 3 mL of 0.5 mol L^?1 HNO₃.     

Modified Calcium Alginate Beads with Sodium Dodecyl Sulfate and Clay as Adsorbent for Removal of Methylene Blue

In present study, we have investigated the effect of an anionic surfactant sodium dodecyl sulfate (SDS) and clay on calcium alginate beads was studied to remove methylene blue (MB) and to improve the adsorption capacity. The effects of various experimental parameters, such as shaking rate, initial dye concentration, temperature, and pH on the adsorption rate, have been studied. Equilibrium studies showed that the sorption of the dye was enhanced in presence of SDS. Scanning electron microscope (SEM) analysis showed that SDS entrapped beads have more pores and cavities which could be responsible for improved adsorption of MB. The kinetics of cationic dye adsorption nicely followed pseudo-second-order process. The evaluated thermodynamic parameters (ΔG ^o, ΔH ^o, ΔS ^o) suggest endothermic adsorption of MB. The results revealed that the surfactant entrapped alginate could be considered as potential adsorbents for MB removal from aqueous solutions.     

多孔氧化铝模板催化制备定向碳纳米管阵列

Well-aligned open-ended multi-walled carbon nanotube (MWCNT) arrays were prepared via chemical vapor deposition (CVD) method in porous anodic aluminum oxide (AAO) templates without depositing any transition metals as catalyst. Effects of the CVD temperature and heat treatment were studied in detail.Well-aligned open-ended MWCNT arrays were obtained at the CVD temperature above 600 ℃; when CVD temperature is reduced to around 550 ℃, CNTs, CNFs and other structures existed at the same time; no CNTs or carbon nanofibres (CNFs) could be found as the CVD temperature is below 500 ℃, and only amorphous carbon in the porous AAO template was found. Experimental results showed that the AAO template is catalytic during the CVD process, and it has the following two effects: to catalyze thermal decomposition of acetylene and to catalyze conversion of carbon decomposed from acetylene into CNTs or CNFs. Heat treatment could improve the graphitization degree, but it might also introduce new defects.