Comparative study of carbide-derived carbons obtained from biomorphic TiC and SiC structures

Biomorphic carbide ceramics, TiC and SiC, derived from paper performs by chemical vapor infiltration were converted into high porous carbon by carbide-derived carbon (CDC) approach using selective etching in chlorine or hydrogen/chlorine gas mixture in a temperature range of 400-1200 °C. A comparative study of both carbide precursors was performed regarding reaction kinetics, influence of hydrogen as well as microstructure of the resulting carbon. SiC showed lower reactivity than TiC. Temperatures below 650 °C are not sufficient to remove Si from SiC. Addition of hydrogen to the reactive gas inhibits the chlorination reaction. A linear decrease of etching rate with increasing hydrogen/chlorine ratio was observed for both carbide precursors. A critical ratio, where no etching takes place, was estimated to be 0.72 for TiC-CDC and 0.66 for SiC-CDC. The etching rate of TiC is independent from the temperature. In the case of SiC activation energy of the chlorination reaction of about 50 kJ/mol was estimated in the temperature range 650-800 °C. The structural ordering of CDC with increasing synthesis temperature affects also its oxidation resistance as shown by thermo gravimetric analysis.     

A general strategy for synthesis of metal oxide nanoparticles attached on carbon nanomaterials

We report a general strategy for synthesis of a large variety of metal oxide nanoparticles on different carbon nanomaterials (CNMs), including single-walled carbon nanotubes, multi-walled carbon nanotubes, and a few-layer graphene. The approach was based on the π-π interaction between CNMs and modified aromatic organic ligands, which acted as bridges connecting metal ions and CNMs. Our methods can be applicable for a large variety of metal ions, thus offering a great potential application.     

A theoretical study on storage states of Li ions in carbon anodes of Li ion batteries using molecular orbital calculations

Semi-empirical molecular orbital calculations were carried out to clarify storage states of Li ions in amorphous carbon anodes of Li ion batteries. Storage states of Li ions between two graphene sheets were investigated and a favorable structure for a carbon anode to produce large reversible and small irreversible capacities is discussed. A polycyclic hydrocarbon molecule, C₅₄H₁₈, was used as a model of a graphene sheet. Relations between the interlayer distance of two graphene sheets and the storage state of Li ions were investigated, and preferable interlayer distances for specific numbers of Li ions were estimated. In particular, storage states with all Li ions on the basal area were treated, because the amount of basal carbons should be larger than that of edge carbons. The charge distribution of Li ions was also investigated. Calculated results suggested that a storage state in which a double Li ion layer was formed was preferable to achieve a larger capacity than the theoretical maximum capacity of graphitic carbons (372 mAh/g) and to reduce hysteresis in the charge-discharge process. Moreover, suitable distance between edges of graphene sheets to prevent the intercalation of electrolyte species was discussed. A recommended structure of carbon anodes suitable for the double Li ion layer storage and prevention of the intercalation of electrolyte species is proposed.     

The Adsorption of Gold,Palladium, and Platinum from Acidic Chloride Solutions on Mesoporous Carbons

Studies on the adsorption characteristics of gold, palladium, and platinum on mesoporous carbon (CMK-3) and sulfur-impregnated mesoporous carbon (CMK-3/S) evaluated the benefits/drawbacks of the presence of a layer of elemental sulfur inside mesoporous carbon structures. Adsorption isotherms collected for Au(III), Pd(II), and Pt(IV) on those materials suggest that sulfur does enhance the adsorption of those metal ions in mildly acidic environment (pH 3). The isotherms collected in 1 M HCl show that the benefit of sulfur disappears due to the competing influence of large concentration of chloride ions on the ion-exchanging mechanism of metal ions sorption on mesoporous carbon surfaces. The collected acid dependencies illustrate similar adsorption characteristics for CMK-3 and CMK-3/S in 1-5 M HCl concentration range. Sorption of metal ions from diluted aqueous acidic mixtures of actual leached electronic waste demonstrated the feasibility of recovery of gold from such liquors.     

Influence of support surface properties on activity of bacteria immobilised on activated carbons for water denitrification

Denitrification of water under anaerobic conditions was carried out by Escherichia coli supported or immobilised on different activated carbons and silica. Results were compared with those obtained when bacteria was used alone or mixed with activated carbons. Denitrification took place in two steps: reduction of nitrate to nitrite, and its subsequent reduction to dinitrogen. The process required an external carbon source that in this case was ethanol. Results obtained in the denitrification process were related to characteristics of activated carbon that favoured bacteria adsorption and to the final pH_PZC of the activated carbon-bacteria complex. In addition, a large macropore volume also allowed the bacteria to grow during the process. The presence of Cd(II) and Cr(VI) ions negatively affected the denitrification process. However, their influence on the removal of nitrite ions was smaller if the bacteria were supported on activated carbon.     

Electrochemical removal of hydrogen sulfide from polluted brines using porous flow through electrodes

Carbon felt was used in porous electrodes to achieve electrochemical oxidation of sulfide ions from flowing chloride brines. Using X-ray photoelectron spectroscopy (XPS) and Energy Dispersive Spectroscopy (EDS), sulfur was identified as the final reaction product under various potentials and temperatures. While some of the resulting sulfur flows out with the electrolyte, the rest remains adsorbed on the graphite surface. The rate of the process and the removal efficiency increase with potential, temperature, flow rate and sulfide concentration. The measured limiting currents are substantially lower than those predicted from mass transfer correlations. This was attributed to the passivating effects of the sulfur deposited on the internal surface of the porous electrode. Potentiostatic current transients show that the carbon felt electrodes have higher capacity for removing sulfide ions than planar electrodes, which is attributed to the large internal surface area of the carbon felt.     

木质素衍生炭在碱金属离子电池负极中的研究进展

碱金属离子在商品化石墨负极材料的嵌入/脱出过程中会发生较大的体积膨胀,导致容量衰减快、倍率性能差等问题。木质素衍生炭材料具有原料丰富、经济、制备工艺简单及结构可控等优点,作为碱金属离子电池负极表现出较高的容量、较好的倍率性能和循环稳定性。木质素衍生炭材料在过去十多年中取得了一些研究进展。基于此,简要介绍了碱金属离子电池碳材料负极的储能机理及特点,系统综述了木质素衍生炭材料在碱金属离子电池负极材料中的最新研究进展,重点总结了其合成策略、结构特征、储存机理以及其电化学性能等,指出了层间距调控、碳层排序和表面功能化与电化学性能之间的构效关系。此外,拓展概述了木质素衍生炭材料的发展前景和面临的挑战,为木质素衍生炭材料的下一步研究和开发提供参考。     

木质素衍生炭在碱金属离子电池负极中的研究进展

碱金属离子在商品化石墨负极材料的嵌入/脱出过程中会发生较大的体积膨胀,导致容量衰减快、倍率性能差等问题。木质素衍生炭材料具有原料丰富、经济、制备工艺简单及结构可控等优点,作为碱金属离子电池负极表现出较高的容量、较好的倍率性能和循环稳定性。木质素衍生炭材料在过去十多年中取得了一些研究进展。基于此,简要介绍了碱金属离子电池碳材料负极的储能机理及特点,系统综述了木质素衍生炭材料在碱金属离子电池负极材料中的最新研究进展,重点总结了其合成策略、结构特征、储存机理以及其电化学性能等,指出了层间距调控、碳层排序和表面功能化与电化学性能之间的构效关系。此外,拓展概述了木质素衍生炭材料的发展前景和面临的挑战,为木质素衍生炭材料的下一步研究和开发提供参考。     

Carbon/SnO2/carbon core/shell/shell hybrid nanofibers: tailored nanostructure for the anode of lithium ion batteries with high reversibility and rate capacity

A carbon/SnO(2)/carbon core/shell/shell hybrid nanofibrous mat was successfully prepared via single-spinneret electrospinning followed by carbonization and hydrothermal treatment. The morphology and structure of carbon/SnO(2)/carbon hybrid nanofibers were characterized by field-emission scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, wide-angle X-ray diffraction and X-ray photoelectron spectroscopy, and their electrochemical properties were studied as an anode in lithium ion batteries (LIBs). It is shown that the designed hybrid nanofibrous mat exhibits excellent electrochemical properties, including high reversible capacity with high columbic efficiency and impressive rate capacity. The greatly enhanced electrochemical performance is mainly due to the morphological stability and reduced diffusion resistance, which are induced by both the carbon core and deposited carbon skin. Furthermore, the embedded and de-aggregated SnO(2) nanoparticles in the carbon phase, which are less than 10 nm in size, provide large numbers of reaction sites for lithium ions and ensure complete alloying with them.     

Use of inorganic catalysts in production of carbon fibres. Properties of the sorbents obtained

The efficiengy of using diffeent inorganic catalytic additives in fabrication of carbon fibre mateials was evaluated by TGA. The important possibility of obtaining CFM with a high yield on the existing equipment at the Svetlogorsk Khimvolokno Industrial Association was demonstrated. The structure and properties of TS and NS carbon materials fabricated with the technology developed were investigated by methods of mercury porosimetry, electron microscopy, cryosorption of nitrogen, sorption of benzene vapors, and sorption of large organic ions. The possibility of using the developed carbon sorbents in purification of virus-containing solutions and for removal of organic contaminants from aqueous solutions was investigated.St. Petersburg State University of Technology and Design. Translated from Khimicheskie Volokna, No. 6, pp. 27–31, November–December, 1996.     

盐酸预处理对浒苔基活性炭电化学性能的影响

传统工艺制备的活性炭微孔足够,但中孔、大孔含量缺乏,导致其用作超级电容器电极材料时电化学性能水平较低。为解决这一问题,采用盐酸对炭化前浒苔原料进行预处理。酸处理去除了原料中大部分的杂质金属,其中,海藻酸钙与盐酸发生化学反应形成了蛋壳初始孔,酸溶性碱金属离子与盐酸发生置换反应形成了无规则初始孔隙,明显增加了活性炭的中孔含量。实验结果表明：盐酸预处理后的活性炭比表面积明显增加,由2273m²/g增至3166m²/g,孔容由2.10cm³/g增至3.82cm³/g,中孔率显著提高,改善了孔结构的连通性,促进了电解质离子在材料内部的扩散;当电流密度为0.1A/g时,经过酸洗处理的活性炭比电容高达359F/g,比原样活性炭比电容的293F/g增长了23%,超级电容器等效串联电阻很小,表现出良好的电化学性能。     

三维电极法去除配位电镀废水中的镍离子和铜离子

将颗粒状活性炭作为三维电极的粒子,采用三维电极法去除配位电镀废水中的镍离子和铜离子。考察了pH值、电流、极板间距、炭水比(粒子电极活性炭与处理水量的体积比)对镍离子和铜离子去除率的影响。在设定的范围内,镍离子和铜离子的去除率随pH值的升高呈现先升后降的变化趋势,随电流和炭水比的增大而升高,随极板间距的增大而降低。当废水中镍离子和铜离子的初始质量浓度分别为82.309 3mg/L和52.761 5mg/L、活性炭的体积为1 000mL、处理时间为2.0h时,最佳的处理工艺条件为:pH值4、电流0.6A,极板间距20cm,炭水比10∶9。此时,镍离子和铜离子的去除率分别为83.40%和86.20%。出水经过混凝沉淀后,镍离子和铜离子的去除率分别达到99.87%和99.68%,在出水中的质量浓度分别为0.107 2mg/L和0.169 3mg/L,出水水质达到《电镀污染物排放标准》(GB 21900—2008)中表2的排放限值。     

活性炭表面负载金属离子对其吸附苯并噻吩的影响

主要研究了活性炭表面负载不同的金属离子对其吸附苯并噻吩的影响.通过浸渍法分别将6种不同的过渡金属离子负载在活性炭表面上,用静态吸附法测定了苯并噻吩硫化物在改性活性炭上的吸附等温线,应用软硬酸碱理论分析和讨论了其吸附能力的差异.结果表明,活性炭表面负载Ag^＋、Ni^2＋、Cu^2＋或Zn^2＋离子,可提高活性炭吸附苯并噻吩硫化物的能力,而活性炭表面负载Fe^3＋或Co^3＋离子,反而降低了活性炭吸附苯并噻吩硫化物的能力,这主要是活性炭表面的酸碱性质发生变化.采用密度泛函数理论法计算结果表明,苯并噻吩的电负性χ为2.638,属软碱类物质;由于Ag^＋为软酸,活性炭负载Ag^＋离子,增加了其局部表面的软酸,从而增强了对苯并噻吩硫化物的吸附;由于Ni^2＋、Cu^2＋和Zn^2＋离子属交界酸,负载Ni^2＋、Cu^2＋、Zn^2＋离子增加了活性炭表面的交界酸,也在一定程度上提高了其表面对苯并噻吩硫化物的吸附;当活性炭表面负载了硬酸性Fe^3＋或Co^3＋离子,其局部表面硬酸增大从而降低了其对苯并噻吩的吸附.     

Simplistic hydrothermal synthesis approach for fabricating photoluminescent carbon dots and its potential application as an efficient sensor probe for toxic lead(II) ion detection

The past decade has witnessed a variety of members of the carbon family along with exposure of carbon dots due to their magnificent properties in sensing, bioimaging, catalytic applications, biomedical fields, and so on. Herein, we report the simple hydrothermal method to fabricate photoluminescent doped carbon quantum dots for the detection of noxious lead(II) ions. Lead(II) ion is very venomous for both the environment and human health for which its detection is demanded area in the research field. The as-prepared carbon dots show excellent photostability, low toxicity and significant photoluminescence properties along with good water solubility. Along with these properties, carbon dots have a quantum yield of approximately 15%. In the practical field of application, these carbon dots have been used as sensing probes for the detection of lead(II) ions with a detection limit of 60 nmol·L^–1. The fluorescence intensity of carbon dots was remarkably quenched in the presence of the lead(II) ion selectively among all the tested metal ions. Furthermore, we have studied the Stern–Volmer relationship for lead(II) quenching along with the explanation of the probable quenching mechanism. Ability of the doped carbon dots in heavy metal ions sensing in an environmental sample was demonstrated.     

Adsorption of zinc, cadmium and mercury ions from aqueous solutions on an activated carbon cloth

The adsorption of zinc, cadmium and mercury ions from aqueous solutions on an activated carbon cloth was studied as a function of their concentrations and solution pH. For that purpose, pertinent adsorption isotherm data was collected at different pH values. The amount of adsorbed zinc and cadmium ions increases while the amount of adsorbed mercury remains constant with an increase in the equilibrium pH of the solution. The adsorption mechanisms of metal ions on activated carbon cloth are discussed. Under the conditions investigated, these primarily involve adsorption of monovalent cations (Zn and Cd) or precipitation of metal hydroxides (Cd and Hg) on the activated carbon cloth tested.     

Binary component sorption of Cu(II) and Pb(II) with activated carbon from Eucalyptus camaldulensis Dehn bark

The objective of this work is to illustrate the potential in the use of activated carbon in the binary component sorption of copper and lead ions. Eucalyptus bark was used as a precursor for the activated carbon which was prepared through the phosphoric acid activation process. This activated carbon was then used for the sorption of copper and lead ions. The quantity of the metal ions in the solution was measured with the Flame & Graphite Furnace Atomic Adsorption Spectrophotometer. The results indicated that the optimal pH for sorption was 5. The maximum sorption capacities for Cu(II) and Pb(II) were 0.45 and 0.53 mmol g⁻¹. Carboxylic, amine and amide groups were found to involve in the sorptions of Cu(II) and Pb(II). A major mechanism for the uptake of both heavy metals was proven not to be ion exchange but adsorption. In binary component sorptions, activated carbon still could sorb Pb(II) in a greater amount than Cu(II). However, the presence of the secondary metal ions suppressed the sorption of the primary metal ions. There seemed to have a linear inverse dependency between the sorption capacity and the concentration of the secondary metal ion.     

A hierarchical porous carbon material for high power, lithium ion batteries

We synthesize a carbon anode material with unique nanostructure for high power lithium ion batteries. The carbon material is composed of numerous clusters of carbon nanobeads, and shows a macro-meso-micro hierarchical porous structure. This unique nanostructure appears to facilitate the rapid transfer of lithium ions and a very large ion adsorption. It exhibits a reversible capacity of 407.4 mAh g⁻¹ and its rate performance is drastically improved in comparison with that of the commercial graphite. The unique structure enables the anode to combine the advantages of both lithium ion batteries and electrochemical double layer capacitors, resulting in the good electrochemical performance.     

非平衡碘负离子转化二氧化碳

以直流脉冲负高压电晕放电形式,通过加入电子亲和能较高的碘气,在完全电负性离子体条件下资源化处理CO₂。考察了进气流量、高压放电频率和原料摩尔比对CO₂转化率的影响。结果表明:70℃时,利用碘负离子成功将CO₂还原生成了CI₄,其产率随着CO₂流量的增加而减少。当进气流量0.06 L·min^-1、放电频率9.608 kHz,n(I₂)/n(CO₂)为2.5时,CO₂转化率在碘负离子作用下达到88.71%。另外,对碘负离子和CO₂还原反应机理进行了初步探讨。     

Removal of sulfide ions from aqueous solutions using carbon- and silicon-containing sorbents

Sulfide ions are among the most common pollutants in natural waters. Sulfide sorption methods are widely used in the waste water treatment practice. The most promising sorbents for removing sulfide ions are porous carbon materials. In the present study we researched sorption capacity of the carbon- and silicon-containing samples of rice and buckwheat processing wastes, as well as the activated carbon, carbon fiber, chitosan and natural silicates toward the sulfide ions in aqueous solutions. It was found that the most effective sorbent from the studied ones is the carbon fiber Aktilen B (99%) and from plant wastes – carbonaceous sorbents obtained from rice straw (77–98%) and buckwheat (94%). We studied the physico-chemical and structural properties of the carbonaceous sorbent based on rice straw and it was found that this sample is amorphous and has a predominant microporous structure. At the concentration of sulfide ions ranging from 140 to 800?µg?l^?1, the studied sorbent reduces the amount of sulfide ions to 0.4–1.4 of the maximum permissible concentration and can be used for treating natural and post-treating waste waters.     

溶剂中金属离子对聚丙烯腈基碳纤维及其原丝的影响

金属离子的含量对碳纤维及其原丝的质量有很大的影响。分析了溶剂二甲基亚砜(DMSO)中金属离子含量对聚丙烯腈(PAN)原液聚合、原丝及碳纤维性能的影响。试验表明:DMSO中金属离子的存在,会在聚合源头处影响聚合反应,造成物料均一性、可纺性、可牵伸性下降,使原丝及碳纤维性能下降;而几种金属离子中,铁离子的干扰破坏性最大。