Adsorption Of Carbon Nanotubes Research Articles

Directed energy deposition of CNTs/AlSi10Mg nanocomposites: Powder preparation, temperature field, forming, and properties

Recently, research of carbon nanotubes (CNTs) doping reinforced aluminum matrix nanocomposites has drawn significant attention. In this study, we conducted annular beam directed energy deposition (DED) experiments using CNTs/AlSi10Mg composites, prepared using a new procedure to improve the laser absorptivity of AlSi10Mg. The effect of the dispersant on CNTs adsorption and that of CNTs adsorption on temperature field, microstructure evolution, formability, and properties were clarified experimentally. The results show that CNTs exhibit good dispersion and adsorption in pure N-methyl pyrrolidone (NMP). Further, grains in the DED track were refined as the CNTs content increased, micro-hardness and laser absorptivity also improved. High-quality thin walls of 0.5- wt%-CNTs/AlSi10Mg were successfully formed, demonstrating that the new DED method for the preparation of CNTs/AlSi10Mg metal matrix nanocomposites is viable, expanding the potential application scenarios of composite material structures.

Experimental and DFT insights into nitrogen and sulfur co-doped carbon nanotubes for effective desulfurization of liquid phases: Equilibrium & kinetic study

Herein, nitrogen and sulfur co-doped carbon nanotubes (NS-CNT) adsorbents were synthesized via the chemical vapor deposition technique at 1000°C by employing the camphor, urea and sulfur trioxide pyridine. In this study, desulfurization of two types of mercaptans (dibenzothiophene (DBT) and tertiary butyl mercaptan (TBM) as nonlinear and linear forms of mercaptan) was studied. In this regard, a maximum capacity of NS-CNT was obtained as 106.9 and 79.4 mg/g and also the removal efficiencies of 98.6% and 88.3% were achieved after 4 h at 298K and 0.9 g of NS-CNT for DBT and TBM, respectively. Characterization of the NS-CNTs was carried out through exploiting scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and elemental analysis (CHN). The isotherm equilibrium data could be ascribed to the Freundlich nonlinear regression form and the kinetic data was fitted by nonlinear form of the pseudo second order model. The negative values of ΔS0, ΔH0 and ΔG0 specify that the adsorption of both types of mercaptans was a natural exothermic process with a reduced entropy. Maintenance of more than 96% of the adsorption capacity even after nine cycles suggest the NS-CNT as a superior adsorbent for mercaptans removal in the industry. Density functional theory (DFT) calculations were also performed to peruse the effects of S/N co-doping and carbon monovacancy defects in CNTs toward the adsorption of DBT and TBM.

Preparation and characteristics of a magnetic carbon nanotube adsorbent: Its efficient adsorption and recoverable performances

The challenges encountered in solid–liquid separation hinder the wide applications of carbon nanotube adsorbents. To overcome this problem, MnFe2O4/multiwalled carbon nanotubes (MMWCNTs) that combined the satisfactory adsorption properties of multiwalled carbon nanotubes (MWCNTs) with the magnetic separation of nanoparticles (MnFe2O4) was developed. MMWCNTs with a size of 10–50 nm exhibited remarkable magnetic separability (10.8 emu/g) and high adsorption capacity (qm = 494.91 mg/g, 308 K). Batch experiments to study the effect of pH on tetracycline (TC) adsorption showed that when the TC concentration was less than 80 mg L−1, the MMWCNTs could effectively adsorb TC in the pH range of 2–10, with a removal efficiency greater than 80%. The well fitted pseudo-second-order dynamic adsorption model and Langmuir isotherm indicated that the TC adsorption onto MMWCNTs mainly involved chemical and monolayer adsorption. Since the TC adsorption process was endothermic, increasing temperature could favor TC removal. Besides, after six cycles of regeneration with the NaOH solution, the removal efficiency could be maintained at 70% of the original, which indicated that the MMWCNTs had an excellent regeneration performance. At the same time, the results of our research showed that MMCWNT could not only be used as a good adsorbent for TC treatment, but also could be applied to other types of wastewater treatment.

Magnetic Multiwall Carbon Nanotube Decorated with Novel Functionalities: Synthesis and Application as Adsorbents for Lead Removal from Aqueous Medium

Water pollution is one of the major challenges facing modern society because of industrial development and urban growth. This study is directed towards assessing the use of multiwall carbon nanotube, after derivatization and magnetization, as a new and renewable absorbent, to remove toxic metal ions from waste streams. The adsorbents were prepared by, first oxidation of multiwall carbon nanotube, then derivatizing the oxidized product with hydroxyl amine, hydrazine and amino acid. The adsorbents were characterized by various techniques. The adsorption efficiency of the multiwall carbon nanotube adsorbents toward Pb(II) was investigated. The effect of adsorbent’s dose, temperature, pH, and time on the adsorption efficiency were studied and the adsorption parameters that gave the highest efficiency were determined. The derivatives have unique coordination sites that included amine, hydroxyl, and carboxyl groups, which are excellent chelating agents for metal ions. The thermodynamic and kinetic results analysis results indicated spontaneous adsorption of Pb(II) by the multiwall carbon nanotube adsorbents at room temperature. The adsorption process followed pseudo-second-order and Langmuir isotherm model. The adsorbents were regenerated using 0.1 N HCl.

Efficient removal of Alizarin Red S from aqueous solution by polyethyleneimine functionalized magnetic carbon nanotubes

Alizarin Red S (ARS) has been extensively used in the dyeing industry. In order to effectively remove the ARS form dyeing wastewater, polyethyleneimine (PEI)-functionalized magnetic carbon nanotubes (PEI@MCNTs) adsorbent was successfully prepared and its adsorption performances were also investigated in detail. The PEI@MCNTs could efficiently remove the ARS from acidic aqueous solution (pH ≤ 6.0) within 40 min under room temperature. Benefiting from a large number of adsorption sites and multiple interactions, PEI@MCNTs possessed high selectivity towards ARS with spontaneous adsorption process. The maximum adsorption capacity of PEI@MCNTs for ARS was 196.08 mg g−1 obtained from Langmuir isotherm, higher than that of available conventional adsorbents. Moreover, the PEI@MCNTs could be easily collected by an external magnet, and then effectively regenerated through 10 mM NaOH solution. The prepared PEI@MCNTs could be considered as the promising adsorbent for the removal of anthraquinone dyes in large-scale wastewater treatment.

Artificial Neural Network Approach for Modelling of Mercury Ions Removal from Water Using Functionalized CNTs with Deep Eutectic Solvent.

Multi-walled carbon nanotubes (CNTs) functionalized with a deep eutectic solvent (DES) were utilized to remove mercury ions from water. An artificial neural network (ANN) technique was used for modelling the functionalized CNTs adsorption capacity. The amount of adsorbent dosage, contact time, mercury ions concentration and pH were varied, and the effect of parameters on the functionalized CNT adsorption capacity is observed. The (NARX) network, (FFNN) network and layer recurrent (LR) neural network were used. The model performance was compared using different indicators, including the root mean square error (RMSE), relative root mean square error (RRMSE), mean absolute percentage error (MAPE), mean square error (MSE), correlation coefficient (R2) and relative error (RE). Three kinetic models were applied to the experimental and predicted data; the pseudo second-order model was the best at describing the data. The maximum RE, R2 and MSE were 9.79%, 0.9701 and 1.15 × 10−3, respectively, for the NARX model; 15.02%, 0.9304 and 2.2 × 10−3 for the LR model; and 16.4%, 0.9313 and 2.27 × 10−3 for the FFNN model. The NARX model accurately predicted the adsorption capacity with better performance than the FFNN and LR models.

One-pot fabrication of magnetic fluorinated carbon nanotubes adsorbent for efficient extraction of perfluoroalkyl carboxylic acids and perfluoroalkyl sulfonic acids in environmental water samples

Efficient extraction of perfluoroalkyl carboxylic acids (PFCAs) and perfluoroalkyl sulfonic acids (PFSAs) is challenging due to their highly fluorinated property. Based on the particular characters of PFCAs and PFSAs, a new type of magnetic fluorinated carbon nanotubes adsorbent (MFCA) for magnetic solid phase extraction (MSPE) was fabricated facilely using one-pot hydrothermal approach. The morphology, structure and magnetic properties of the prepared MFCA were investigated by Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy and vibrating sample magnetometry. It was observed that the resultant adsorbent possessed satisfactory superparamagnetism and saturation magnetism. Furthermore, the MFCA exhibited excellent enrichment performance for target PFCAs and PFSAs by means of fluorous-fluorous, hydrophobic and hydrogen bonding interactions. Under the most favorable preparation and extraction conditions, the proposed MFCA/MSPE was combined with high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) to quantify ultra trace target analytes in environmental water samples. The limits of detection (S/N = 3) of PFCAs and PFSAs were 0.010–0.036 ng/L and 0.024–0.50 ng/L, respectively. In addition, the introduced approach also displayed other features such as quick extraction procedure, wide linear dynamic ranges, excellent method precision and eco-friendliness. Finally, the concentrations of PFCAs and PFSAs in tap, river, lake and waste water samples were successfully measured by isotope internal standard calibration curve method.

Water Molecule Adsorption in Carbon Nanotubes with Haeckelite Structure: First Principles Study

Water Molecule Adsorption in Carbon Nanotubes with Haeckelite Structure: First Principles Study

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.

Phosphate Adsorption from Solution by Zirconium-Loaded Carbon Nanotubes in Batch Mode

A highly effective zirconium-modified carbon nanotube (Zr-CNTs) adsorbent was prepared to remove phosphate (PO43–) from solution in batch mode. Characterizations of Zr-CNTs were analyzed using FTIR...

Removal of Cadmium Chloride from Contaminated Residual Soil using Carbon Nanotubes (CNTs)

Industrial waste inorganic pollutants are normally produced from mineral compounds, such as for example heavy metals, salts, and minerals. These inorganic pollutants can be managed by selecting the appropriate removal techniques. By implementing the removal technique, the number of contaminants may decrease as pollutants reach the soils during certain reaction periods because of chemical reactions and sorption. These reactions depend on both the additive removal material in use, the soil and the environment's chemical characteristics. In soil contamination, reaction rates can be experimentally monitored, and the adsorption mechanism can be measured. The aim of this paper is to experimentally observe the mechanism of heavy metal removal of cadmium chloride in contaminated residual soils using carbon nanotube (CNT) adsorbent. In this research, a series of multi-wall carbon nanotube (MWCNTs) adsorption experiments were used to evaluate the adsorption of residual soil contaminants Cadmium chloride with a concentrations range of 50-200 mg / L. The tests were conducted with different weights of MWCNTs and a concentration of 50 to 200 mg / L of Cadmium Chloride contaminant. The temperature was thoroughly investigated on kinetics and the equilibrium of sorption contaminants in MWCNTs. It shows that MWCNT's can be used to remove heavy metal pollutants, evaluated based on the adsorption mechanism of Langmuir and Freundlich's isotherm models, from the contaminated residual soil as an effective adsorbent. As regards adsorbent models, the balance data in the Freundlich equation are reasonably proven compared to the Langmuir isotherm. As regards adsorbent models, the equilibrium data in the Freundlich equation are reasonably proven compared to the Langmuir isotherm.

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.

Assembly and electrochemistry of carbon nanomaterials at the liquid-liquid interface

The interfacial adsorption of single-walled carbon nanotubes and few-layer graphene flakes, prepared by solution phase exfoliation, is compared. Strong adsorption of carbon nanotubes was observed at the water/1,2-dichloroethane interface, while a weaker adsorption of the graphene dispersion was seen. Addition of electrolyte to the organic phase was found to have a strong effect on the adsorption of graphene. A simple surface energy model does not fully explain these observations, rather residual charges and their distribution appears to be the key factor behind this difference in adsorptive behaviour. Carbon nanomaterials adsorbed at the liquid-liquid interface can function as bipolar electrodes: a preliminary investigation of the oxidation of the 1,2-dichlorobenzene by metal-modified graphene particles is performed.

Selected Heavy Metals Removal From Electroplating Wastewater by Purified and Polyhydroxylbutyrate Functionalized Carbon Nanotubes Adsorbents

This research investigated the removal of heavy metals (As, Pb, Cr, Cd, Ni, Cu, Fe, and Zn) via batch adsorption process from industrial electroplating wastewater using two different nano-adsorbents; purified carbon nanotubes (P-CNTs) and polyhydroxylbutyrate functionalized carbon nanotubes (PHB-CNTs), both produced through catalytic chemical vapour deposition (CCVD) method. HRSEM, HRTEM, XRD, DLS, BET, FTIR, XPS, TGA, pH drift and Raman spectroscopy were used to characterize the developed nano-adsorbents. In the batch adsorption process, the effects of contact time, dosage, temperature and pH were studied. Both nano-adsorbents gave optimum contact time, equilibrium time, optimum dosage, and pH of 10 minutes, 70 minutes, 20 mg, and 5.63–5.65 respectively. The heavy metals removal efficiencies by the nano-adsorbents followed the order of PHB-CNTs > P-CNTs based on ion exchange and electrostatic forces mechanism. For P-CNTs and PHB-CNTs, the equilibrium sorption isotherm suits temkin model, kinetic data fitted to pseudo-second order based on the linear regression correlation coefficient, and the thermodynamic study established spontaneity and endothermic nature of the adsorption process. The findings in this research conclude that both nano-adsorbents have exceptional capacity to remove heavy metals from the adsorbate, with PHB-CNTs possessing better quality. The treated adsorbate meets the standard for industrial or irrigation re-use.

Cross-Linked Carbon Nanotube Adsorbents for Water Treatment: Tuning the Sorption Capacity through Chemical Functionalization.

The development of carbon-based membrane adsorbent materials for water treatment has become a hot topic in recent years. Among them, carbon nanotubes (CNTs) are promising materials because of its large surface area, high aspect ratio, great chemical reactivity, and low cost. In this work, free-standing CNT adsorbents are fabricated from chemically cross-linked single-walled CNTs. We have demonstrated that by controlling the degree of cross-linking, the nanostructure, porous features, and specific surface area of the resulting materials can be tuned, in turn allowing the control of the adsorption capacities and the improvement of the adsorption performance. The cross-linked CNT adsorbents exhibit a notably selective sorption ability and good recyclability for removal of organics and oils from contaminated water.

Adsorption properties of magnetic carbon nanotubes for patulin removal from aqueous solution systems

Patulin (PAT) is a type of mycotoxin produced by the P. expansum, Aspergillus, Penicillium, and Paecilomyces fungal species and constitutes serious food-related and environmental health threats to consumers. In this study, a novel magnetic multi-walled carbon nanotube (MWCNT) adsorbent was successfully synthesized, and its adsorption properties for the efficient removal of PAT from aqueous solution were investigated. The effects of adsorption parameters, such as pH, initial PAT concentration, adsorption time and temperature, were investigated for optimization of the adsorption process. The kinetic and isotherm studies revealed that PAT adsorption was well described by a pseudo-second order model and the Freundlich model, respectively. The maximum adsorption capacity of the as-prepared magnetic MWCNTs reached 640.2 μg/g, which was much higher than that of biological material-based absorbents (p < 0.05), and the adsorption equilibrium time was significantly shortened to 1 h (p < 0.05). Thermodynamic studies revealed that the adsorption process was exothermic. The adsorption activation energy determined from the Arrhenius equation was found to be approximately −27.31 kJ mol−1, suggesting that the adsorption of PAT on magnetic MWCNTs was random and spontaneous in nature within the experimental temperatures. Moreover, the recycling, separation and regeneration of the spent magnetic MWCNTs were evaluated, and the results demonstrated that the spent magnetic MWCNTs could be separated magnetically and regenerated by sodium hydroxide solution for recycling uses up to four cycles without significantly losing adsorption efficiency. Therefore, this novel magnetic MWCNT-based adsorbent could be a potential adsorbent to be applied for PAT removal from many aqueous systems.

Prediction of the sorption coefficient for the adsorption of PAHs on MWCNT based on hybrid QSPR-molecular docking approach

In this study, quantitative structure–property relationship (QSPR) methodology employed for modeling of the sorption coefficient (log KCNT) of 13 polycyclic aromatic hydrocarbons (PAHs) on multiwall carbon nanotube (MWCNT) adsorbent. A molecular docking simulation used to present a reliable and accurate QSPR model with defining the distance and best orientation of PAHs structures on nano-adsorbent. A genetic algorithm-multiple linear regression method was employed for implementation of QSPR model. In this model, the square of correlation coefficients (R2) was 0.945 and 0.890, and the root mean square errors (RMSE) were 0.08 and 0.18 for the training and test sets, respectively. Also, inspection to selected descriptors indicates the electrostatic and steric parameters of PAHs are the predominant factors responsible on the log KCNT values. These results can be used for prediction of sorption coefficient of other PAHs by MWCNT and modify the surface of the adsorbent for improving the log KCNT.

Functionalized carbon nanotube adsorption interfaces for electron transfer studies of galactose oxidase

Modified electrodes featuring specific adsorption platforms able to access the electrochemistry of the copper containing enzyme galactose oxidase (GaOx) were explored, including interfaces featuring nanomaterials such as nanoparticles and carbon nanotubes (CNTs). Electrodes modified with various self-assembled monolayers (SAMs) including those with attached nanoparticles or amide-coupled functionalized CNTs were examined for their ability to effectively immobilize GaOx and study the redox activity related to its copper core. While stable GaOx electrochemistry has been notoriously difficult to achieve at modified electrodes, strategically designed functionalized CNT-based interfaces, cysteamine SAM-modified electrode subsequently amide-coupled to carboxylic acid functionalized single wall CNTs, were significantly more effective with high GaOx surface adsorption along with well-defined, more reversible, stable (≥ 8 days) voltammetry and an average ET rate constant of 0.74 s−1 in spite of increased ET distance - a result attributed to effective electronic coupling at the GaOx active site. Both amperometric and fluorescence assay results suggest embedded GaOx remains active. Fundamental ET properties of GaOx may be relevant to biosensor development targeting galactosemia while the use functionalized CNT platforms for adsorption/electrochemistry of electroactive enzymes/proteins may present an approach for fundamental protein electrochemistry and their future use in both direct and indirect biosensor schemes.

Measurement of Carbon-Nanotube Adsorption of Energy-Carrier Gases for Alternative Energy Systems

Measurement of Carbon-Nanotube Adsorption of Energy-Carrier Gases for Alternative Energy Systems

Integrated QMMM and Monte Carlo methods for analysis of adsorptive interactions between goethite cluster, carbon nanotubes, and arsenate

AbstractIron‐immobilized nanoporous carbon is a well‐known adsorbent used in treating arsenic‐contaminated waters. In this contribution, we present findings on the adsorptive interactions and dynamics of arsenate–goethite cluster ([FeO(OH)]6) with carbon nanotubes (CNTs) using hybridized quantum mechanics/molecular mechanics (QMMM) calculations. The CNTs adsorption mechanism is of interest since a better understanding of the fundamental interactions between arsenate, goethite, and carbon surfaces would translate to advances in CNT‐based adsorbent production and utilization. Novel applications of general amber force field (GAFF) and isobaric‐isothermal Gibbs ensemble Monte Carlo (NpT‐GEMC) methods are described. By the abovementioned methods, we postulate that the [FeO(OH)]6/CNT‐2.3 (diameter 2.3 nm ‐ mesoporous) system enhances the qualitative (i.e., improved chemisorption) rather than the quantitative adsorptive aspect (i.e., total ions adsorbed) in comparison to the [FeO(OH)]6/CNT‐1.6 (diameter 1.6 nm ‐ microporous) system.