As-prepared Carbon Nanotubes Research Articles

Aiming the water transport issues of anion exchange membrane fuel cells by introducing hydrophobic carbon nanotube diffusion layer

The gas diffusion layer (GDL) enhances the transport efficiency of reaction gases and facilitates the removal of accumulated liquid water, thereby improving water management in anion exchange membrane fuel cells (AEMFCs). Carbon nanotubes (CNTs) are recognized as one of the promising materials to optimize mass transport within GDLs. In this study, we successfully synthesized an abundance of CNTs on the surface of commercial gas diffusion media. The as-prepared CNT layer exhibits exceptionally high hydrophobic properties and forms a hierarchically hydrophobic structure combined with the gas diffusion media, effectively enhancing the mass transfer of the membrane electrode assembly (MEA) and reducing ohmic impedance. Under supersaturation conditions, the power density of the MEA containing CNTs reaches 1031.7 mW/cm2, significantly higher than the 760.64 mW/cm2 observed for the commercial GDL. Further testing demonstrates that the MEA containing CNTs exhibits a limiting current density of 2507.4 mA/cm2, which is much superior to the benchmark MEA with the commercial GDL (1591 mA/cm2). Electrochemical impedance spectroscopy analysis reveals that the mass transfer resistance of MEAs with CNTs is lower than that of MEAs with the commercial GDL. More importantly, the phase-field modeling is performed to simulate the transport of the liquid water in the hierarchical GDL.

Kinetic Modulation of Carbon Nanotube Growth in Direct Spinning for High-Strength Carbon Nanotube Fibers.

With impressive individual properties, carbon nanotubes (CNTs) show great potential in constructing high-performance fibers. However, the tensile strength of as-prepared carbon nanotube fibers (CNTFs) by floating catalyst chemical vapor deposition (FCCVD) is plagued by the weak intertube interaction between the essential CNTs. Here, we developed a chlorine (Cl)/water (H2O)-assisted length furtherance FCCVD (CALF-FCCVD) method to modulate the intertube interaction of CNTs and enhance the mechanical strength of macroscopic fibers. The CNTs acquired by the CALF-FCCVD method show an improvement of 731% in length compared to that by the conventional iron-based FCCVD system. Moreover, CNTFs prepared by CALF-FCCVD spinning exhibit a high tensile strength of 5.27 ± 0.27 GPa (4.62 ± 0.24 N/tex) and reach up to 5.61 GPa (4.92 N/tex), which outperforms most previously reported results. Experimental measurements and density functional theory calculations show that Cl and H2O play a crucial role in the furtherance of CNT growth. Cl released from the decomposition of methylene dichloride greatly accelerates the growth of the CNTs; H2O can remove amorphous carbon on the floating catalysts to extend their lifetime, which further modulates the growth kinetics and improves the purity of the as-prepared fibers. Our design of the CALF-FCCVD platform offers a powerful way to tune CNT growth kinetics in direct spinning toward high-strength CNTFs.

Fabrication of Carbon Nanotubes Derived from Waste Tire Pyrolytic Carbon and Their Application in the Dehydrogenation of Methylcyclohexane to Produce Hydrogen

The accumulation of waste tires has resulted in very urgent environmental problems. Pyrolysis has been regarded as a green eco-friendly technology to deal with waste tires, and it is vital to make use of the pyrolysis carbon. Herein, we propose a new way to utilize pyrolysis carbon, to prepare carbon nanotubes with the help of ferrocene. The optimal preparation processes were determined by optimizing the parameters including the solvent, temperature, time, etc. The results of scanning electron microscopy and transmission electron microscopy evidenced the successful formation of carbon nanotubes. Meanwhile, the Brunauer–Emmett–Teller (BET) method and N2-adsorption showed that the yielded carbon nanotubes featured a large surface area and abundant pore structure in comparison with the pyrolytic carbon. Finally, the as-prepared carbon nanotubes were applied as the supports for Pt-based catalysts for the dehydrogenation of methylcyclohexane to produce hydrogen. The results showed that the Pt/carbon-nanotubes catalyst exhibited the highest conversion of methylcyclohexane (28.6%), stability, and hydrogen evolution rate (336.9 mmol/gPt/min) compared to the resulting Pt/commercial-activated-carbon (13.6% and 160.2 mmol/gPt/min) and Pt/pyrolytic-carbon catalysts (0.19% and 2.23 mmol/gPt/min).

Chemisorption Effect Enables High-Loading Zinc-Iodine Batteries

Rechargeable Zn-I2 batteries featuring intrinsic safety and high energy density demonstrate promising energy storage prospects. However, the poor interface stability of the Zn anode and the undesirable shuttle effect severely hinder the device stability due to the diffusive characteristics of the soluble polyiodides in aqueous media. Here, a synergetic physicochemical strategy that combines physical constraints and chemical absorption was proposed by developing a composite host matrix with a core/porous-sheath structure, which can effectively confine iodine species. Initial I− ions bind securely with carboxylated multi-walled carbon nanotubes (c-MCNTs) to form the C–I bonds through chemical interactions. Furthermore, the pore structure of microporous carbon (MPC) not only restricts the iodine species in the pores through physisorption (secondary adsorption) but also facilitates the diffusion of Zn2+. The as-prepared carbon nanotubes coated with microporous carbon (glucose as the carbon source, and its ratio to CNT is 12:1) can serve as a host material (CNT@MPC12), and adsorb iodide ions to derive CNT@MPC12-I−. As a result, the developed aqueous Zn battery with CNT@MPC12-I− cathode delivers superior reversible rate capacity (0.35mAh cm–2 at 20mAcm–2) and remarkable cycling performance (12000 cycles at 10mAcm–2). Notably, such cathode can also exhibit an impressive capacity retention of 97% after 8600 cycles, even at an ultrahigh loading mass of 16.05mgcm–2. As such, our strategy can be extended to design other metal I2 batteries with high loading and long-life expectancy.

High compaction and physical graphitization of CNT bundles and network via extreme-load compression using laser-induced shockwave

The physical properties of carbon nanotube (CNT) networks, which are one-dimensional assemblies of CNTs, are still far short of the theoretical limits of individual CNTs. These lowered physical properties of CNT networks are mainly due to their high porosity and relatively weak inter-tube load/electron/phonon transfer efficiency at van der Waals junctions between CNTs and their bundles. We present a simple post-treatment technique utilizing high-intensity laser-induced shockwaves of up to ∼3 GPa that effectively densify CNT bundles and networks and physically transform CNT bundles into flattened multilayered graphene nanoribbons. CNT assemblies were selectively modified without chemical agents, and the network properties could be tuned by adjusting the laser compression intensity. After laser shockwave compaction, the CNT network structure showed two and three times higher specific strength and modulus than the as-prepared CNT networks. Furthermore, the thermal and electrical conductivities of the CNT networks were also amplified by 400–500% after laser shock compression. These enhancements can be explained by the substantial densification of CNT networks and physically activated graphitization leading to increased load/electron/phonon transfer between flattened CNTs and their bundles.

Synergistic Effect of Field Emission Properties on Growth of CNTs by One-Pot Preparation of Various Concentrations Composite Catalyst

Multi-walled carbon nanotubes (MWCNTs) were grown on Silicon (Si) substrate by using low-pressure chemical vapor deposition (LPCVD) technique where iron (Fe) and silver (Ag) colloidal solution act as a catalyst were prepared by chemical route. The as-prepared solutions in varied concentrations were deposited on a Si substrate using a spin coating process at 700[Formula: see text]rpm. The purpose of Fe in composite catalysts is to have high carbon solubility and diffusion rate, and Ag utilization can change catalyst activity temperature and enhance carbon yields. In this work, we demonstrate the growth of carbon nanotubes (CNTs) on different catalyst concentrations ([Formula: see text]Fe/[Formula: see text]Ag), ([Formula: see text]Fe/[Formula: see text]Ag), ([Formula: see text]Fe/[Formula: see text]Ag) and ([Formula: see text]Fe/[Formula: see text]Ag) catalytic films. Field Emission Scanning Electron Microscopy (FESEM) was used to image the morphologies of various catalyst concentrations MWCNTs. The natures of the synthesized CNTs were determined using Raman spectroscopy and it was revealed that as-prepared CNTs are MWCNTs due to the absence of radial breathing mode (RBM). Raman spectroscopy demonstrated the lower ID/IG ratio (Ratio of the intensity of D-Raman peak and G-Raman peak) of ([Formula: see text]Fe/[Formula: see text]Ag) MWCNTs. The ID/IG ratio for ([Formula: see text]Fe/[Formula: see text]Ag) catalyzed MWCNTs was 0.76, while the ID/IG ratio for ([Formula: see text]Fe/[Formula: see text]Ag) catalyzed MWCNTs was 0.89. The ([Formula: see text]Fe/[Formula: see text]Ag) catalyzed MWCNTs were found to be more defective as compared to other. Electron Emission from ([Formula: see text]Fe/[Formula: see text]Ag) catalyzed MWCNTs were much stronger than from other samples, as demonstrated by Field Emission measurement using diode configuration. The turn-on field for ([Formula: see text]Fe/[Formula: see text]Ag) catalyzed MWCNTs was (0.92 V/[Formula: see text]m) which is slightly lower than that of ([Formula: see text]Fe/[Formula: see text]Ag) catalyzed MWCNTs (1.83 V/[Formula: see text]m), indicating superior enhancement.

Torsional Properties of Bundles with Randomly Packed Carbon Nanotubes.

Carbon nanotube (CNT) bundles/fibers possess promising applications in broad fields, such as artificial muscles and flexible electronics, due to their excellent mechanical properties. The as-prepared CNT bundles contain complex structural features (e.g., different alignments and components), which makes it challenging to predict their mechanical performance. Through in silico studies, this work assessed the torsional performance of CNT bundles with randomly packed CNTs. It is found that CNT bundles with varying constituent CNTs in terms of chirality and diameter exhibit remarkably different torsional properties. Specifically, CNT bundles consisting of CNTs with a relatively large diameter ratio possess lower gravimetric energy density and elastic limit than their counterpart with a small diameter ratio. More importantly, CNT bundles with the same constituent CNTs but different packing morphologies can yield strong variation in their torsional properties, e.g., up to 30%, 16% and 19% difference in terms of gravimetric energy density, elastic limit and elastic constants, respectively. In addition, the separate fracture of the inner and outer walls of double-walled CNTs is found to suppress the gravimetric energy density and elastic limit of their corresponding bundles. These findings partially explain why the experimentally measured mechanical properties of CNT bundles vary from each other, which could benefit the design and fabrication of high-performance CNT bundles.

Facile Synthesis of Birnessite δ-MnO2 and Carbon Nanotube Composites as Effective Catalysts for Li-CO2 Batteries.

Li-CO2 batteries are one type of promising energy storage and conversion devices to capture and utilize the greenhouse gas CO2, mitigating global temperature rise and climate change. Catalysts that could effectively decompose the discharge product, Li2CO3, are essential for high-performance Li-CO2 batteries. Benefiting from the interconnected porous structure, favorable oxygen vacancy, and the synergistic effects between the carbon nanotube (CNT) and layered birnessite δ-MnO2, our Li-CO2 cathodes with the as-prepared CNT@δ-MnO2 catalyst can efficiently afford a large reaction surface area and abundant active sites, provide sufficient electron/Li+ transport pathways, and facilitate electrolyte infiltration and CO2 diffusion, demonstrating low overpotential and superior cycling stability, which have been proven by both experimental characterization and theoretical computation. It is expected that this work can provide guidance for the design and synthesis of high-performance electrochemical catalysts for Li-CO2 batteries.

Impacts from the stacking morphology on the tensile performance of double-walled carbon nanotube bundles

Carbon nanotube (CNT) based fibers/films are envisioned as the building blocks for next generation high-performance composite materials. However, the mechanical performance of the as-synthesized or as-prepared CNT bundles are still well below their constituent CNTs. Here, we systematically assessed the influence from the stacking morphology on the tensile properties of double-walled CNTs (DWNTs)-based bundles through molecular dynamics simulations. We found that the bundles containing zigzag DWNTs exhibit higher Young’s modulus, but lower yielding strength (and yielding strain) compared with that of the pure armchair DWNT-based bundles. In particular, an initial off-axial angle perturbation in one of the constituent DWNTs induces evident misalignments in other constituent DWNTs, which remarkably degrades the yielding strength and yielding strain of the bundle structures. Following the Hooke’s law, the impacts from the stacking morphology on the overall tensile properties of DWNT bundles can be quantitatively predicted by approximating each DWNT as an elastic column approximation. Overall, this work establishes a comprehensive understanding of the influence from the stacking morphology, which not only provides a perspective explanation of the unexpected low performance of as-synthesized CNT bundles, but also shed light on the design of high-performance CNT based bundles.

Fabrication of vertically aligned N-doped carbon nanotube arrays on vermiculite by horizonal chemical vapor deposition

Efficient synthesis of large-scale vertically aligned nitrogen-doped carbon nanotube arrays (VA-NCNTs) has always been a challenge. In this study, we proposed a facile way to obtain mass VA-NCNTs between vermiculite layers by horizonal chemical vapor deposition (CVD). Vermiculite with layered compound as the catalyst substrate, Fe and Mo as the active metal phase is evenly distributed between the vermiculite layers, melamine is pyrolyzed as a single source for both carbon and nitrogen to synthesize nitrogen-doped carbon nanotube (CNT) array materials with relatively uniform length and diameter at an optimum temperature of 800 °C. We explored the effect of temperature on synthesis of VA-NCNTs, the results indicated that the VA-NCNTs are sensitive to temperature changes during the CVD synthesis process, the arrangement, diameter, nitrogen content, and the type of nitrogen function of CNTs could be modified. This work contributes to the study of how the growth temperature affecting the morphology of the as-prepared CNTs, and provides a potential method for the controllable mass production of oriented NCNTs.

One-step copper-catalyzed synthesis of porous carbon nanotubes for high-performance supercapacitors

The supercapacitor with high power density, long cycling life, security and reliability is a kind of energy storage device that attracts currently much attention. Porous carbon nanotubes with large specific surface area and excellent electrical conductivity are a promising electrode material for supercapacitors. A simple bottom-up synthesis strategy is proposed for porous carbon nanotubes. The carbon dioxide as a carbon source is converted to carbon and then deposited on the surface of the copper powder that plays a catalytic role, and the carbon atoms are arranged in an orderly manner at high temperature to form porous carbon nanotubes. The factors that affect the growth of porous carbon nanotubes are found. The relationships between these factors and the morphology and structure of porous carbon nanotubes are discussed to reveal the growth of porous carbon nanotubes. In addition, the as-prepared porous carbon nanotubes exhibit a high specific surface area and excellent electrochemical performances, which can maintain a high specific capacitance under a large current density and a high sweep rate. The assembled symmetric supercapacitor successfully provides energy for small devices. • Copper was first discovered to catalyze the synthesis of porous carbon nanotubes. • Carbon dioxide serves as the carbon source to prepare porous carbon nanotubes by a bottom-up strategy. • The factors that affect the growth of carbon nanotubes are found and discussed in detail. • The porous carbon nanotubes exhibit high special capacitance (300.1 F g −1 ) and outstanding cycling stability.

Tailored CNTs Buckypaper Membranes for the Removal of Humic Acid and Separation of Oil-in-Water Emulsions.

Carbon nanotubes (CNTs) are a robust material and proven as a promising candidate for a wide range of electronic, optoelectronic and environmental applications. In this work, two different methods were utilized for the preparation of CNTs exhibiting different aspect ratios via chemical vapor deposition (CVD). The as-prepared CNTs were analyzed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2adsorption isotherms, thermogravimetric analysis and Raman spectroscopy in order to investigate their morphological and structural properties. Free-standing CNTs “buckypaper” membranes were fabricated, characterized and tailored to meet the requirements of two applications, i.e., (1) the removal of humic acid (HA) from water and (2) separation of oil-in-water emulsions. It was revealed that the hydrophobic buckypapers showed high separation performance for Shell oil-in-water emulsions filtration, with up to 98% through the accumulation of oil droplets onto the membrane surface. The absorption capacity of buckypaper membranes for various organic liquids (oil, chloroform and toluene) was evaluated over 10 absorption cycles to investigate their recyclability and robustness. Moreover, surface modification was introduced to the pristine CNTs to increase their surface hydrophilicity and improve the pure water permeability of buckypapers. These modified buckypapers showed high flux for HA solutions and excellent HA rejection efficiency up to 95%via size exclusion and electrostatic repulsion mechanisms.

Study on carbon nanotubes and activated carbon hybrids by pyrolysis of coal

Carbon nanotubes (CNTs) and activated carbon (AC) hybrids were obtained by co-pyrolysis of potassium hydroxide and bituminous coal. Scanning electron microscopy (SEM), thermogravimetric analysis (TGA), Raman spectroscopy, X-ray Diffraction (XRD), and nitrogen adsorption measurements were used to investigate the characteristics of the samples and the effects of the final pyrolysis temperature and time on the structure of the carbon materials. The results indicated that the optimal range for the pyrolysis temperature and time for CNT growth were 900–950 °C and 45–90 min, respectively. The diameters of the as-prepared CNTs were in the range of 50–250 nm and their lengths were ∼15 μm. During the pyrolysis process, potassium hydroxide not only acted as the catalytic precursor to catalyze the CNT growth but also reacted with carbon to produce abundant micropores. Furthermore, the content of CNTs in the product after demineralization was significantly reduced. It was further confirmed by Inductively Coupled Plasma (ICP) analysis that the content of Fe, Co, and Ni decreased after demineralization, indicating that minerals in coal play an important role in the growth of coal-based CNTs.

N-doped hard carbon nanotubes derived from conjugated microporous polymer for electrocatalytic oxygen reduction reaction

The development of efficient non-metal catalysts (NMC) towards oxygen reduction reaction (ORR) in both acidic and alkaline electrolyte is of great importance for construction of new generation fuel cell. Herein, we demonstrate the fabrication of N-doped hard carbon nanotubes prepared by carbonization of melamine-incorporated nanotube-like conjugated microporous polymers (CMPs), as novel electrocatalysts for efficient ORR. As a kind of metal-free electrocatalyst, the as-prepared carbon nanotubes exhibit superior ORR activity not only in alkaline electrolyte but also in acidic condition. Interestingly, obvious enhancement on the diffusion-limited current density (increased by 1.8 mA cm−2) for the N-doped products in acid solution is observed by comparison with that of carbonized CMPs nanotubes without N-doping. Furthermore the catalysts also show better methanol immunity than that of commercial 20 wt% Pt/C. And only a slight decrease (14 mV negative shift) in half-wave potential is detected after 5000 cycles in 0.1 M KOH, indicating an ideal electrochemical stability which makes the N-doped hard carbon nanotubes promising candidate as an efficient electrocatalyst for ORR, by combination with their desirable electrocatalytic ORR activity, methanol tolerance and stability.

Evaluation of carbon-based nanostructures suitable for the development of black pigments and glazes

Five different carbon-based samples were chosen for the fabrication of black pigments and glazes: historical ‘unknown’ wood charcoal, graphite, tailored graphitized soot, as-prepared multi-walled carbon nanotubes (MWCNTs) and purified MWCNTs. Ceramic glazes with carbon pigments were prepared with Pb3O4 and SiO2 in molar ratio of 2.85:1.9 and using 5 wt. % of pigment at 900 °C. The black pigments and glazes were characterized by scanning electron microscopy (SEM), optical microscopy, diffuse reflectance spectroscopy and contact angle measurements. International Commission on Illumination (CIE) parameters L*, a* and b* (CIELab-parameters) of the samples were also determined. It was demonstrated that nanostructured carbon pigments showed better black colour and higher quality of black ceramic glaze. Our investigation let us to conclude that these results possibly were affected by initial microstructure of applied carbon derivatives. The obtained nanostructured carbon black pigments could be successfully used for artefact restoration.

Bioinspired synthesis of polyzwitterion/titania functionalized carbon nanotube membrane with superwetting property for efficient oil-in-water emulsion separation

Oil/water separation membranes with high flux efficiency and robust anti-oil-fouling property have attracted numerous attention, and superwetting carbon nanotube (CNT) membranes are promising candidates. The key challenges focus on the versatile integration of multiple materials/structures and the facile functionalization towards superhydrophilicity/underwater superoleophobicity. In this study, a polyzwitterion/titania functionalized carbon nanotube membrane for antifouling and high-flux oil/water emulsion separation is synthesized by a novel and simple dual-bioinspired strategy. The strategy involves the co-assembly of polyzwitterion and bioinspired-adhesive polydopamine (PDA) modified CNTs and the bioinspired mineralization of titania nanoparticles (TNPs). The as-prepared CNT membrane is evenly decorated with polyzwitterion and TNPs mediated by the comprehensive adhesive capability of PDA. The integration of the hydrophilic advantages of polyzwitterion and titania and the integration of the multiscale structures of CNTs and TNPs endow membranes with superhydrophilicity, underwater superoleophobicity and anti-oil-adhesion property. The nanoscale porous structures of CNT assembled network ensure the high permeability (about 3400 L m−2 h−1) and separation efficiency (over 99.5% for emulsified oils) of membranes. Furthermore, when applied to oil-in-water emulsion separation, the as-prepared CNT membrane exhibits good recycle performance throughout several filtration cycles and maintains high recovery ratio of 95% after several cycles, indicating excellent antifouling property. The dual-bioinspired strategy combining bioinspired adhesion and bioinspired mineralization provides new insights into the design and construction of nano-structured membranes for oil/water separation.

A novel flexible UV-cured carbon nanotube composite film for humidity sensing

A new flexible resistor-type humidity sensor was developed based on UV-cured carbon nanotube composite film as humidity-sensing material. Carbon nanotubes (CNTs) were firstly mixed with UV-curable resin via ball-milling. Simply by spin-coating of this mixture on flexible interdigitated electrode and subsequent UV-curing, a flexible humidity sensor based on UV-cured CNTs composite film was thus fabricated. With the utilization of UV-curing technology, this fabricating strategy is rather simple, highly efficient (accomplished in several minutes), cost-effective, and environmental-friendly (no organic solvent). The effect of the CNTs content, the nature of the UV-curable resin as well as their ratios on the humidity-sensing performance was systematically investigated. Under optimized conditions, the UV-cured CNTs composite film showed remarkable sensing performance over a wide humidity span from 6% to 84%. In addition, the as-prepared CNTs composite film exhibited small hysteresis and fast response. Moreover, good repeatability and long-term stability was demonstrated. This work offers a novel, economical and promising way to fabricate humidity sensors considering the facile, efficient and green preparation strategy and outstanding sensing properties.

Controllable synthesis of N-doped aligned carbon nanotubes from melamine-based carbon by water-assisted chemical vapor deposition

N-doped well-aligned thin multiwall carbon nanotubes (CNTs) have been prepared by a facile water-assisted chemical vapor deposition (CVD) process using melamine as both the carbon precursor and N-dopant and ferrocene as both the catalyst and carbon precursor. It is shown that the synthetic temperature has strong effects on the growth of carbonaceous structure. Carbon films started to grow at reaction temperature of 700 °C, and the optimal temperature for the synthesis of aligned CNTs, based on the experiment results, was found to be 900 °C. The lengths of the CNTs can be tuned by changing the annealing time of the pyrolysis process, it could reach as long as 40.2 μm. The atomic percentage of nitrogen doping in aligned CNTs could be achieved to 1.71%. It was found that there were many joints and defects in the as-prepared CNTs which may offer more nucleation sites on the chemically inert CNT surface for various specialized applications such as supercapacitor.

Introducing the Kabachnik–Fields multicomponent reaction for functionalization of multiwalled carbon nanotubes and their performance for removal of methylene blue

Abstract The development of functionalized carbon nanotubes (CNTs) for environmental application is an area of research that holds great promise and intense interest. In this study, an organic-inorganic CNTs composite was synthesized via a novel “one-pot” route and was used as an adsorbent for removal of methylene blue (MB) from aqueous solution. At first, furfural as a diene was covalently anchored onto the surface of pristine CNTs through the Diels–Alder (DA) cycloaddition reaction. Then, the Kabachnik–Fields (KF) reaction, a nearly century-old multicomponent reaction, was rediscovered as an efficient “connector” which conveniently builds up polymer architectures on CNTs surfaces under rather mild conditions (including air atmosphere, aqueous solution, and catalyst-free). The surface morphology and chemical structure were analyzed by transmission electron microscopy, thermal gravimetric analysis, and X-ray photoelectron spectroscopy. Moreover, adsorption characteristics of MB on the as-prepared CNTs adsorbents were examined by varying experimental conditions such as contact time, solution pH, temperature and initial MB concentration. It was shown that the removal process was pH dependent. Kinetics indicated that the adsorption equilibrium can be achieved within 20 min and experimental data were best described by the pseudo-second-order model. The adsorption isotherms data were preferably fitted to the Langmuir model, yielding the maximum adsorption capacity of 346.88 mg/g. The thermodynamic study suggested that the adsorption process is endothermic and spontaneous in nature. It is concluded that the possible mechanisms of adsorption may be attributed to π–π stacking or electrostatic interaction. These results suggested that the modified CNTs based composite is expected to be a new candidate for dye removal. More importantly, we believe that the current work paves a facile and green way to fabricate new libraries of CNTs/polymer functional materials via the combination of DA reaction and KF reaction and might prompt the broader study of the KF reaction in interdisciplinary fields.

Synthesis, electron microscopy properties and adsorption studies of Zinc (II) ions (Zn2+) onto as-prepared Carbon Nanotubes (CNTs) using Box-Behnken Design (BBD)

The high levels of zinc (II) ions (Zn2+) have long been harmful to the environment and this study explored the feasibility of adsorption of Zn2+ on as-prepared carbon nanotubes (CNTs) from simulated aqueous solutions in batch-model process. The as-prepared CNT using chemical vapor deposition (CVD) technique was systematically characterized using electron microscopy techniques. Effects of adsorption parameters were modeled using Box-Behnken design (BBD) of experiment and 99.50% Zn2+ ions removal was achieved at adsorbent dosage, 50 mg; pH, 6.0; contact time, 60 min and contact speed, 125 rpm. The Langmuir, Freundlich and Temkim adsorption isotherms were used to verify the as-prepared CNTs adsorption performance. It was found that the adsorption data were well fitted to the Langmuir model. Moreover, the kinetic studies revealed that the adsorption kinetic data follows a pseudo-second-order model. The results indicate high prospect of the as-prepared CNTs for Zn2+ ion removal.