Synthesis of graphene/hollow carbon fiber composite aerogels for oil spill cleanup

To solve environmental problems caused by the spill of oil and other organic liquids, we have developed graphene/hollow carbon fiber composite aerogels (G-CF) with a low density, high hydrophobicity, buoyancy, and adsorption capacity up to 42.7 g g^–1.     

Facile fabrication of hydrophobic octadecylamine-functionalized polyurethane foam for oil spill cleanup

To improve the hydrophobic property of polyurethane foam for oil spill cleanup, the polyurethane foam with nitrile groups is modified by grafting with oleophilic octadecylamine. Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and optical contact angle measuring device are used to characterize the modified polyurethane foam. The results show that the octadecylamine has been successfully grafted onto the polyurethane foam and improved the foam hydrophobicity. The modified foam exhibits higher contact angle (146.3 ± 2.8°) compared to the unmodified foam (121.4 ± 3.2°). Moreover, the water sorption of the modified foam is 0.11g/g, which is much lower than that of the unmodified foam (0.84g/g). On the other hand, the sorption capacity of the modified foam for toluene, gasoline and diesel sorption is increased by 20?40%. Therefore, the polyurethane foam prepared by us can be effectively used in oil/solvent spill cleanup.     

Adsorptive performance of MWCNTs for simultaneous cationic and anionic dyes removal; kinetics,thermodynamics, and isotherm study

Disposal of contaminated wastewater causes many serious problems especially when it gets mixed with the ground and seawater. It is, therefore, important to apply any remedial action to eradicate dangerous pollutants from the aqueous effluents and to avoid exposure of this wastewater to aquatic life. The research results discussed herein deal with the removal of Rhodamine B (RhB) and Congo Red (CR) dye from wastewater by using multi-walled carbon nanotubes (MWCNTs) as an adsorbent. Different factors like solid dosage, initial pH and concentration, time, and temperature were studied to understand the behavior and mechanism of adsorption. The maximum adsorption capacity in case of a single component system was found to be 302 mg/g and 300 mg/g for Congo Red and Rhodamine B, respectively. Moreover, the mechanism of adsorption was best described by a pseudo-second-order kinetic model. Thermodynamic parameters showed that adsorption of CR and RhB was exothermic when these were removed from a single dye system. However, the overall process became endothermic for concurrent removal of both dyes from the solution. The research results showed that the MWCNTs could successfully be utilized to remove the dye from the industrial wastewater.     

Multi-Walled Carbon Nanotubes and Powder-Activated Carbon Adsorbents for the Removal of Nitrofurazone from Aqueous Solution

Multi-walled carbon nanotubes (MWCNTs) and powder-activated carbon (PAC) were used as adsorbents for adsorption of nitrofurazone, a veterinary medicine, from aqueous solutions. The adsorbents were characterized using FTIR transform infrared spectroscopy, N₂ adsorption/desorption isotherms, and scanning electron microscopy. The effects of initial pH, contact time, and temperature on adsorption capacity of the adsorbents were investigated. For MWCNT and PAC, the result showed that when the pH value was ranged from 2.0 to 10.0, the dosage of adsorbent was 0.02 g, and adsorptive time is 4 hours, the removal efficiencies for nitrofurazone were 96.8% and 94.7%, and the corresponding maximum capacities at 283 K were close to 50.8 mgg^?1 and 59.9 mgg^?1, respectively. For nitrofurazone, the pseudo-second-order kinetic model provided the best fit to the experimental data. The Boyd model indicated the mechanism for adsorption processes was mainly external mass transfer, while the effect of particle internal diffusion was relatively weak. Liu model could best fit to the experimental data of isothermal adsorption. The data of adsorption thermodynamics showed that the adsorption process was spontaneous.     

含多壁碳纳米管的硅胶整体柱的制备、表征及性能评价

制备了一种新的含多壁碳纳米管的硅胶整体柱,并用扫描电子显微镜和比表面积测试仪对其进行了表征.利用正己烷为流动相,考察了该整体柱的流速与渗透率和流速与柱压降的关系,以及苯取代化合物在该整体柱上的色谱保留行为,并对其在分离过程中的作用机理进行了探讨.     

Comparison of different cleanup procedures for oil crops based on the development of a trace analytical method for the determination of pyraclostrobin and epoxiconazole

The effects of different cleanup procedures in removing high‐molecular‐mass lipids and natural colorants from oil‐crop extracts, including dispersive solid‐phase extraction, low‐temperature precipitation and gel permeation chromatography, were studied. The pigment removal, lipid quantity, and matrix effects of the three cleanup methods were evaluated. Results indicated that the gel permeation chromatography method is the most effective way to compare the dispersive solid‐phase extraction and low‐temperature precipitation. Pyraclostrobin and epoxiconazole applied extensively in oil‐crop production were selected as typical pesticides to study and a trace analytical method was developed by gel permeation chromatography and ultra high performance liquid chromatography with tandem mass spectrometry. Average recoveries of the target pesticides at three levels (10, 50, and 100 μg/kg) were in the range of 74.7–96.8% with relative standard deviation values below 9.2%. The limits of detection did not exceed 0.46 μg/kg, whereas the limits of quantification were below 1.54 μg/kg and much lower than maximum residue limit in all matrices. This study may provide the essential data for optimizing the analytical method of pesticides in oil‐crop samples.     

Hydrogen adsorption in carbon nanostructures: comparison of nanotubes, fibers, and coals

Single-walled carbon nanotubes (SWNT) were reported to have record high hydrogen storage capacities at room temperature, indicating an interaction between hydrogen and carbon matrix that is stronger than known before. Here we present a study of the interaction of hydrogen with activated charcoal, carbon nanofibers, and SWNT that disproves these earlier reports. The hydrogen storage capacity of these materials correlates with the surface area of the material, the activated charcoal having the largest. The SWNT appear to have a relatively low accessible surface area due to bundling of the tubes; the hydrogen does not enter the voids between the tubes in the bundles. Pressure-temperature curves were used to estimate the interaction potential, which was found to be 580+/-60 K. Hydrogen gas was adsorbed in amounts up to 2 wt % only at low temperatures. Molecular rotations observed with neutron scattering indicate that molecular hydrogen is present, and no significant difference was found between the hydrogen molecules adsorbed in the different investigated materials. Results from density functional calculations show molecular hydrogen bonding to an aromatic C[bond]C that is present in the materials investigated. The claims of high storage capacities of SWNT related to their characteristic morphology are unjustified.     

Adsorption of NOM onto Activated Carbon: Effect of Surface Charge, Ionic Strength, and Pore Volume Distribution

Adsorption of natural organic matter (NOM) onto seven activated carbons with a wide range of surface properties was studied at high and low ionic strength over a range of pH values. From adsorption isotherm studies it was found that, for six of seven carbons, at low surface concentrations, increased ionic strength decreased NOM adsorption. As the surface concentration increased, the adsorption isotherms converged and intersected, after which the addition of salt resulted in increased adsorption. This “crossover point” marked a change in the adsorption mechanism from the “screening reduced” to the “screening enhanced” adsorption regimes. The adsorption mechanisms are extremely complicated and appear attributable to various factors, including electrostatic forces, pore volume distribution, and chemical interactions between the NOM and the surface functionalities on the carbon surfaces.     

Flexural,impact, rheological and physical characterizations of POM reinforced by carbon nanotubes and paraffin oil

The paraffin oil dispersion technique innovated in the recent years to synthesize bulk polymer nanocomposite materials has a uniform dispersion. This research work aims to study the effect of added carbon nanotubes (CNTs) on flexural, impact and rheology behaviors of polyoxymethylene (POM) reinforced by 0–0.03 wt% of CNT using paraffin oil dispersion technique. The wettability and lamellar thickness were measured and rheological performance investigated using a parallel plate rheometer. The flexural and impact mechanical properties were also evaluated. The fracture surfaces were then examined by microscopy. The results showed that the energy to break, flexural strength and modulus increased proportionally with the addition of the amount of CNT in the matrix. For the rheology behavior, the viscosity decreased at the low percentage of CNT and then increased with increase in the percentage weight ratio of CNT in the POM matrix. It was also noted that the water contact angle rose with the increase the CNT percentages. Copyright © 2016 John Wiley & Sons, Ltd.     

Preparation, properties and cytotoxicity evaluation of a biodegradable polyester elastomer composite

Multi-walled carbon nanotube (MWCNT)/poly(glycerol–sebacate–citrate) (PGSC) elastomer composite were prepared and their morphologies, compositions, glass transition temperatures, mechanical properties, water absorption, biodegradation and cytotoxicity were investigated. Results showed that the chemical structures of PGSC elastomers were hardly influenced by the MWCNT loadings, and physical adsorption was thought as the main interaction between the MWCNTs and PGSC matrixes. When the MWCNT loading was 3 wt%, MWCNTs displayed a homogenous dispersion in the matrixes, and the composite's strength and modulus respectively reached 4.4 MPa and 9.2 MPa, increasing by 62.96% and 33.33% than that of pure PGSC matrixes. The degradation rates of the composites tended to decrease with the increase of MWCNT loadings in simulated body fluid (SBF) solution. The composites presented no cytotoxicity especially when the MWCNT loadings were above 1 wt%. We expect the composites can be used as degradable bio-coatings and tissue engineering scaffolds in future.     

磁性镍基氮掺杂多壁碳纳米管对双酚A的吸附性能及机理研究

通过简单的高温煅烧法制备了具有较大比表面积的磁性镍基氮掺杂多壁碳纳米管材料(Ni-NMC-NTs),将该材料用于双酚A(BPA)的吸附研究,对材料吸附前后的形貌和结构变化进行表征,探究其吸附机理.结果表明:具有中空管状结构的磁性Ni-NMCNTs对BPA具有良好的吸附能力和重复利用性,材料中n比啶氮的存在提供了吸附缺陷...     

Development and evaluation of porous materials for carbon dioxide separation and capture

The development of new microporous materials for adsorption separation processes is a rapidly growing field because of potential applications such as carbon capture and sequestration (CCS) and purification of clean-burning natural gas. In particular, new metal-organic frameworks (MOFs) and other porous coordination polymers are being generated at a rapid and growing pace. Herein, we address the question of how this large number of materials can be quickly evaluated for their practical application in carbon dioxide separation processes. Five adsorbent evaluation criteria from the chemical engineering literature are described and used to assess over 40 MOFs for their potential in CO(2) separation processes for natural gas purification, landfill gas separation, and capture of CO(2) from power-plant flue gas. Comparisons with other materials such as zeolites are made, and the relationships between MOF properties and CO(2) separation potential are investigated from the large data set. In addition, strategies for tailoring and designing MOFs to enhance CO(2) adsorption are briefly reviewed.     

碳纳米管负载的铂催化剂对柠檬醛选择加氢及CO微分吸附热研究

碳纳米管(CNTs)是近年来发现的一种新型催化剂载体材料,将其作为α,β-不饱和醛的选择加氢的研究则报道较少．本文对柠檬醛[Citral,3,7-二甲基-2,6-辛二烯醛(3,7-Dimethyl-2,6-octadienal)]在Pt／CNTs和Pt／XC-72催化剂作用下的液相选择加氢进行了探索性研究．结果发现,碳纳米管(CNTs)负载的Pt催化剂具有生成不饱和醇的高选择性．     

Critical evaluation and comparison of enrichment efficiency of multi-walled carbon nanotubes, C18 silica and activated carbon towards some pesticides from environmental waters

In this work, optimization of multi-residue solid phase extraction (SPE) procedures coupled with high-performance liquid chromatography for the determination of Propoxur, Atrazine and Methidathion from environmental waters is reported. Three different sorbents were used in this work: multi-walled carbon nanotubes (MWCNTs), C18 silica and activated carbon (AC). The three optimized SPE procedures were compared in terms of analytical performance, application to environmental waters, cartridge re-use, adsorption capacity and cost of adsorbent. Although the adsorption capacity of MWCNT was larger than AC and C18, however, the analytical performance of AC could be made close to the other sorbents by appropriate optimization of the SPE procedures. A sample of AC was then oxidized with various oxidizing agents to show that ACs of various surface properties has different enrichment efficiencies. Thus researchers are advised to try AC of various surface properties in SPE of pollutants prior to using expensive sorbents (such as MWCNT and C18 silica).     

Nitrogen‐Doped Carbon Nanotube Arrays for High‐Efficiency Electrochemical Reduction of CO2: On the Understanding of Defects,Defect Density,and Selectivity

Nitrogen‐doped carbon nanotubes (NCNTs) have been considered as a promising electrocatalyst for carbon‐dioxide‐reduction reactions, but two fundamental chemistry questions remain obscure: 1) What are the active centers with respect to various defect species and 2) what is the role of defect density on the selectivity of NCNTs? The aim of this work is to address these questions. The catalytic activity of NCNTs depends on the structural nature of nitrogen in CNTs and defect density. Comparing with pristine CNTs, the presence of graphitic and pyridinic nitrogen significantly decreases the overpotential (ca. ?0.18 V) and increases the selectivity (ca. 80 %) towards the formation of CO. The experimental results are in congruent with DFT calculations, which show that pyridinic defects retain a lone pair of electrons that are capable of binding CO₂. However, for graphitic‐like nitrogen, electrons are located in the π* antibonding orbital, making them less accessible for CO₂ binding.     

A comparative study of biochar,multiwalled carbon nanotubes and graphitized carbon black as QuEChERS absorbents for the rapid determination of six triazole fungicides by UPLC-MS/MS

A rapid, effective and sensitive method to quantitatively determine six fungicide residue was developed using ultra-performance liquid chromatography coupled with tandem mass spectrometry (UPLC–MS/MS). The target compounds were extracted by using acetonitrile and the sorbent used for clean-up in this modified QuEChERS analytical method were biochar, multiwalled carbon nanotubes (MWCNT) and graphitized carbon black (GCB). Results indicated that the MWCNT (10 mg) was the most effective sorbent in removing pigment. This method was validated on spinach, tomato, cucumber, celery, lettuce, rape, pakchoi, romaine lettuce and eggplant matrices spiked at three concentration levels of 0.01, 0.1 and 1 mg kg^?1. It exhibited recoveries between 73.1% and 118.2% with RSD values below 20%. Matrix-matched calibrations were performed with the coefficients of determination >0.9901 between concentration levels of 0.01–1 mg kg^?1. The limit of quantity (LOQ) for six pesticides ranged from 0.0036 to 0.011 mg kg^?1. The developed method was satisfactorily applied to determine pesticide residues in market vegetable samples.     

Comparison of parallel flow and concentric micronebulizers for elemental determination in lubricant oil, residual fuel oil and biodiesel by Inductively Coupled Plasma Optical Emission Spectrometry

Two micronebulizers, PFA-100 and Miramist, were evaluated using a method for elemental determination by Inductively Coupled Plasma Optical Emission Spectrometry (ICP OES) in lubricant and residual fuel oils diluted in xylene. The facility and speed of direct sample dilution in organic solvents, without additional pretreatment, combined with the multielemental capacity and robustness of ICP OES are advantageous. The operational conditions were optimized through factorial design. Improvement in the signal-to-background ratio was observed for Ag, Al, B, Ba, Ca, Cr, Cu, Fe, Mn, Si, Ti and V. Higher sensitivity was obtained with the PFA-100 micronebulizer, although the limits of detection (LOD) obtained for both micronebulizers were similar, between 0.3 μg kg^-1 (Mg) and 18 μg kg^-1 (Ni). The certified reference materials NIST 1634c and NIST 1085b were used for method validation and good recoveries were obtained with values between 93% (Pb) and 102% (P) for PFA-100 and 90% (Pb) and 103% (P) for Miramist. The method was also validated for analysis of biodiesel samples by recovery tests, with results from 89% to 103%. The proposed method was employed for the analysis of crude oil, lubricant oil and biodiesel from different raw materials.     

A New,Simple and Versatile Strategy for the Synthesis of Short Segments of Zigzag‐Type Carbon Nanotubes

Short segments of zigzag single‐walled carbon nanotubes (SWCNTs) were obtained from a calixarene scaffold by using a completely new, simple and expedited strategy that allowed fine‐tuning of their diameters. This new approach also allows for functionalised short segments of zigzag SWCNTs to be obtained; a prerequisite towards their lengthening. These new SWCNT short segments/calixarene composites show interesting behaviour in solution. DFT analysis of these new compounds also suggests interesting photophysical behaviour. Along with the synthesis of various SWCNTs segments, this approach also constitutes a powerful tool for the construction of new, radially oriented π systems.     

Hybrid Fibers Made of Molybdenum Disulfide,Reduced Graphene Oxide,and Multi‐Walled Carbon Nanotubes for Solid‐State,Flexible, Asymmetric Supercapacitors

One of challenges existing in fiber‐based supercapacitors is how to achieve high energy density without compromising their rate stability. Owing to their unique physical, electronic, and electrochemical properties, two‐dimensional (2D) nanomaterials, e.g., molybdenum disulfide (MoS₂) and graphene, have attracted increasing research interest and been utilized as electrode materials in energy‐related applications. Herein, by incorporating MoS₂ and reduced graphene oxide (rGO) nanosheets into a well‐aligned multi‐walled carbon nanotube (MWCNT) sheet followed by twisting, MoS₂‐rGO/MWCNT and rGO/MWCNT fibers are fabricated, which can be used as the anode and cathode, respectively, for solid‐state, flexible, asymmetric supercapacitors. This fiber‐based asymmetric supercapacitor can operate in a wide potential window of 1.4 V with high Coulombic efficiency, good rate and cycling stability, and improved energy density.     

Preparation of HMWCNT/PLLA nanocomposite scaffolds for application in nerve tissue engineering and evaluation of their physical,mechanical and cellular activity properties

This study was aimed to prepare biodegradable and porous nanocomposite scaffolds with microtubular orientation structure as a model for nerve tissue engineering by thermally induced phase separation (TIPS) method using dioxane as the solvent, crystalline poly (L‐lactic acid) (PLLA) and multi‐walled carbon nanotubes (MWCNTs). In order to overcome dispersion of MWCNTs in the PLLA matrix, heparinization of MWCNTs was performed. Solvent crystallization, oriented structure, the mean pore diameter and porosity percentage of the scaffolds were controlled by fundamental system parameters including temperature‐gradient of the system, polymer solution concentration and carbon nanotube content. Scanning Electron Microscopy (SEM), ImageJ, software and dynamic mechanical thermal analysis (DMTA) were used to investigate the structural and mechanical properties. TEM observation was carried out for characterization of nanotube dispersion in PLLA. It was found that the scaffolds containing heparinized multi‐walled carbon nanotubes (HMWCNTs) exhibited higher storage modulus, better carbon nanotube (CNT) dispersion and tubular orientation structure than those with non heparinized MWCNTs. In‐vitro studies were also conducted by using murine P₁₉ cell line as a suitable model system to analyze neuronal differentiation over a 2‐week period. Immunofluorescence and DAPI staining were used to confirm the cells' attachment and differentiation on the PLLA/HMWCNT nanocomposite scaffolds. Based on the results, we can conclude that the PLLA/HMWCNT scaffolds enhanced the nerve cell differentiation and proliferation, and therefore, acted as a positive cue to support neurite outgrowth. Copyright © 2015 John Wiley & Sons, Ltd.