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2014, 29(1)

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Abstract:

Recent advances in molecular imprinting technology for the deep desulfurization of fuel oils

Yong-zhen1, 2, 　LIU Xu-guang 1, 3

2014, 29(1): 1-14. doi: 10.1016/S1872-5805(14)60121-9

Abstract(1101)

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As a novel adsorptive desulfurization method for the preparation of adsorbents, molecular imprinting technology is used to create specific molecular recognition sites in polymers to identify sulfur-bearing template molecules. It is a green process with potential applications because of its characteristics of mild conditions, simple operation, low investment, low pollution, high selectivity, no effect on octane value, and the possible reuse of the as-obtained benzothiophene-like compounds as fine chemicals. Recently, inorganic materials including silica gel, TiO2, K2Ti4O9, and carbon microspheres have been used as supports to prepare surface molecularly imprinted polymers for adsorbing dibenzothiophene and benzothiophene. Recent advances in molecular imprinting technology for deep desulfurization are summarized with carbon microsphere surface molecular imprinting technology highlighted. The review provides experimental references and theoretical guidance for designing and preparing green desulfurization materials.

Adsorption performance of carboxylated multi-wall carbon nanotube-Fe3O4 magnetic hybrids for Cu(II) in water

De-li1, *, 　LI Hui1, 　HE Hua1, 2, 　LIN Rui3, 　ZUO Peng-li1

2014, 29(1): 15-25. doi: 10.1016/S1872-5805(14)60122-0

Abstract(924)

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Carboxylated multi-wall carbon nanotube (c-MWCNT)-Fe₃O₄ magnetic hybrids (c-MWCNTMCs) were prepared by mixing FeCl₃·6H₂O, sodium acetate, ethylene glycol and diethylene glycol with c-MWCNTs, followed by sonicating and heat treatment at 200℃ for 10h. Results indicated that the c-MWCNTMCs showed a good dispersion stability, an acid and alkali resistivity, and magnetic properties in deionized water, and can be used as adsorbents for Cu(II) removal . The c-MWCNTMCs could be easily separated from water by a magnet and showed a high adsorption capacity for Cu(II). The adsorption of Cu(II) on the c-MWCNTMCs was quick and followed a pseudo-second-order model. The adsorption force between the c-MWCNTMHs and Cu(II) was of a chemical type and the saturated adsorbents can be regenerated at pH < 2.0. The magnetic Fe₃O₄ favored only the quick separation and had little contribution to adsorption. The low limit of Cu(II) in water that was removable with the hybrids was 1.29μg/L.

Self-assembly of carbon nanotubes modified by hydropropyl cellulose in aqueous solution

WANG Guo-jian 1, 2, 　LIU Yang1, 　WU Ying-jie1

2014, 29(1): 26-33.

Abstract(1050)

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Hydropropylcellulose (HPC)-modified multi-wall carbon nanotubes (HPC-MWCNTs) were prepared by physical adsorption of HPC on the surface of MWCNTs. The modification decreased the contact angle of water on HPC-MWCNTs and increased their water dispersion ability. However, HPC-MWCNTs dispersed in water were not stable and precipitated on the bottom of the container after 2 days as cylindrical bundles with a diameter of 4-8μm and a length of 25-35μm. The cylindrical bundles were formed by self-assembly of HPC-MWCNTs by hydrophilic and hydrophobic interactions.Hydropropylcellulose (HPC)-modified multi-wall carbon nanotubes (HPC-MWCNTs) were prepared by physical adsorption of HPC on the surface of MWCNTs. The modification decreased the contact angle of water on HPC-MWCNTs and increased their water dispersion ability. However, HPC-MWCNTs dispersed in water were not stable and precipitated on the bottom of the container after 2 days as cylindrical bundles with a diameter of 4-8μm and a length of 25-35μm. The cylindrical bundles were formed by self-assembly of HPC-MWCNTs by hydrophilic and hydrophobic interactions.

Field emission properties of carbon nanocoils synthesized on stainless steel

LI Li-li, 　PAN Lu-jun, 　LI Da-wei, 　ZHAO Qin, 　MA He

2014, 29(1): 34-40. doi: 10.1016/S1872-5805(14)60123-2

Abstract(964)

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Abstract:
Carbon nanocoils (CNCs) were synthesized by a thermal chemical vapor deposition (CVD) method over tin-coated type 202 stainless steel (SS) plates (Cr 15%, Mn 10%, Ni 1%). It is considered that the calcination at 900℃ leads to the crazing of the SS surface, which causes the Fe (Ni) and Sn to be fully mixed and forms active Fe (Ni)-Sn-O catalyst particles suitable for the growth of CNCs. However, the Cr in the catalyst particles is below the limitation of detection, and its role is currently not understood. The electron field-emission properties of as-grown CNCs dispersed on an n-type Si substrate were also investigated. It is found that the CNCs exhibit a low turn-on electric field of 1.6V/m. The distributions of electric fields on a stand-up and a laid-down CNC successfully explain the behavior of the Fowler-Nordheim (F-N) plot. The field enhancement factor for the laid-down CNC is 2.25 times larger than that for a laid-down multiwall carbon nanotube (CNT). This is because the helical morphology of the CNCs can reduce the screening effect produced by the surrounding substrate. In this case, CNCs can more easily emit electrons, and show promise for use in X-ray sources, field emission displays and other micro- or nano-devices.

Microvoid evolution in carbon fibers during graphitization for the preparation of carbon/carbon composites

WU Gang-ping1, 　LI Deng-hua1, 　YANG Yu1, 　LU Chun-xiang1, 　ZHANG Shou-chun1

2014, 29(1): 41-46. doi: 10.1016/S1872-5805(14)60124-4

Abstract(908)

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Abstract:

Polyacrylonitrile-based carbon fiber bundles, with two sides fixed, were heated in a graphitization furnace with temperature profiles similar to those used in the preparation of carbon/carbon composites. The microstructure of the microvoids formed was characterized by small-angle X-ray scattering and high resolution transmission electron microscopy (HR-TEM). Results showed that the average radius of gyration of the microvoids decreases, and their length, width, cross-sectional area and volume fraction decrease followed by a slight increase with increasing temperature, with the minima found at around 2300℃. The HR-TEM images showed that the microvoids were formed by stacking defects of the carbon layers. The ordering of the amorphous carbon layers accounted for the initial decrease of size and volume fraction of the voids with increasing temperature, while the growth and ordering of the layers at high temperatures gave rise to increases in their size and volume fraction.

Rice straw-derived activated carbons for the removal of carbofuran from an aqueous solution

CHANG Ken-Lin1, CHEN Chih-Cheng2, LIN Jun-Hong3, HSIEH Jung-Feng4, WANG Yin1, ZHAOFen

2014, 29(1): 47-54. doi: 10.1016/S1872-5805(14)60125-6

Abstract(926)

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Abstract:
Activated carbon was prepared from rice straw by carbonization and KOH activation, and was used as an adsorbent for the removal of a kind of pesticide, carbofuran (2,3-dihydro-2,2-dimethylbenzofuran-7-yl methylcarbamate) from aqueous solution. The effects of the initial carbofuran concentration, contact time, temperature and pH, on its adsorption capacity and kinetics were studied using a batch method. The surface area and average pore diameter of the activated carbon were 1304.8m²/g and 2.39nm, respectively. The maximum adsorption capacity of the activated carbon (296.52mg/g) for carbofuran was found to occur at 90min, 30℃ and 200mg/L initial carbofuran concentration with an adsorbent loading of 100mg/L. Equilibrium adsorption isotherms were fitted better by the Langmuir model than the Freundlich and Temkin models. The adsorption follows a pseudo-second-order kinetics model.

Activated carbons produced from depleted fullerene soot by carbon dioxide activation and their electrochemical properties

SUN Li, 　WANG Chun-lei, 　ZHOU Ying, 　ZHANG Xu, 　QIU Jie-shan

2014, 29(1): 55-60.

Abstract(1083)

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Abstract:
Activated carbons (ACs) were prepared by CO₂activation using depleted fullerene soot as precursor. The structure of the ACs was investigated by TEM, XRD, and nitrogen adsorption. Their electrochemical properties in electrochemical capacitors were tested by cyclic voltammetry (CV) and galvanostatic charge/discharge methods in a three-electrode cell. Activation temperature and time were proved to be key parameters in controling the development of porosity and surface area of the ACs. The ACs have an excellent electrochemical performance with fast charge/discharge characteristics. AC activated at 1173K for 2h exhibits an excellent electrochemical performance even at a high scanning rate of 400mV·s^-1 with a quasi-rectangular CV curve and its specific capacitance is up to 126F·g^-1 at a high current density of 4A·g^-1.

Selective reduction of graphene oxide

XU Chao1, 　YUAN Ru-sheng 1, 　WANG Xin2

2014, 29(1): 61-66. doi: 10.1016/S1872-5805(14)60126-8

Abstract(1458)

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Abstract:
The reduction of graphene oxide has been widely used to control the properties of graphene-based materials. Traditional methods thoroughly remove oxygenated functional groups in graphene oxides. We show that ethanol, ethylene glycol and glycerol can selectively reduce epoxy groups in graphene oxide while hydroxyl and carboxyl groups remain unchanged. Hydrazine hydrate can reduce oxygen functional groups except carboxyl groups. These selective removals can be used to control the reduction degree of graphene oxides and their properties. The electrical conductivity of the reduced graphene oxides with different types of oxygen functional groups varied significantly and increased with the degree of reduction.

Kinetic model of gas-phase reactions in the chemical vapor deposition of propane

XU Wei1, ZHANG Zhong-wei2, BAI Rui-cheng1, LI Ai-jun1, WANG Jun-shan2, SUN Jin-liang

2014, 29(1): 67-77.

Abstract(992)

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Abstract:
The chemical kinetics of propane pyrolysis in chemical vapor deposition (CVD) is investigated in 1074 reactions consisting of 285 species to understand chemistry of CVD from propane. The reaction mechanism is modeled in a perfectly stirred reactor and a continuous tubular reactor, to produce a 0-D and a 1-D propane pyrolysis model, respectively. The concentration profiles of gas-phase products in the axial direction of the reactor as functions of temperature and residence time are computed with the DETCHEM software package designed for computing time-dependent homogeneous reactions. Comparison between simulated and experimental results shows that the mechanism gives the formation pathway for all major products and can predict the concentration profiles of minor products. Main reaction paths and crucial reaction steps have been determined at 1248K for 1s by analyzing the flux of the main products. The significant roles of radicals such as propargyl, cyclopentadienyl and indenyl in the formation of polyaromatic hydrocarbons were discussed.

Easy synthesis of poly(ionic liquid) for use as a porous carbon precursor

LIAO Chen1, *, 　LIU Rui1, 　HOU Xi-sen1, 　SUN Xiao-guang1, 　DAI Sheng1, 2

2014, 29(1): 78-80. doi: 10.1016/S1872-5805(14)60127-X

Abstract(907)

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Abstract:

　A novel poly(ionic liquid) which can be used as a carbon precursor was synthesized using a one-pot reaction using 1,2-dimethylimidazole and epichlorohydrin as starting materials. The unique features of this poly(ionic liquid) include: no additional initiator is required; anions can be metathesized to regulate the micropore size of the carbonaceous materials. Carbonaceous materials derived from the poly(ionic liquid) with chloride anions (Cl^-) as counter ions have a low surface area of 47m²/g. However, by replacing Cl^- with a bulky bis(trifluoromethylsulfonyl)imide (TFSI^-) anion, the carbonaceous materials produced have a high surface area of 595m²/g, while replacing Cl^- with dicyanoimide (N(CN)2^-) anion results in a reduced surface area of 30m²/g. Keywords:　Poly(ionic liquid); Carbon precursor; Porosity

2014 Vol. 29, No. 1

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