Characteristics of Nonafluorobutyl Methyl Ether (NFE) Adsorption onto Activated Carbon Fibers and Different-Size-Activated Carbon Particles

The characteristics of adsorption of 1,1,1,2,2,3,3,4,4-nonafluorobutyl methyl ether (NFE), a chlorofluorocarbon (CFC) replacement, onto six different activated carbon; preparations (three activated carbon fibers and three different-sized activated carbon particles) were investigated to evaluate the interaction between activated carbon surfaces and NFE. The amount of NFE adsorbed onto the three activated carbon fibers increased with increasing specific surface area and pore volume. The amount of NFE adsorbed onto the three different-sized-activated carbon particles increased with an increase in the particle diameter of the granular activated carbon. The differential heat of the NFE adsorption onto three activated carbon fibers depended on the porosity structure of the activated carbon fibers. The adsorption rate of NFE was also investigated in order to evaluate the efficiency of NFE recovery by the activated carbon surface. The Sameshima equation was used to obtain the isotherms of NFE adsorption onto the activated carbon fibers and different-sized-activated carbon particles. The rate constant k for NFE adsorption onto activated carbon fibers was larger for increased specific surface area and pore volume. The rate of NFE adsorption on activated carbons of three different particle sizes decreased with increasing particle diameter at a low initial pressure. The adsorption isotherms of NFE for the six activated carbons conformed to the Dubinin-Radushkevich equation; the constants BE(0) (the affinity between adsorbate and adsorbent) and W(0) (the adsorption capacity) were calculated. These results indicated that the interaction between the activated carbon and NFE was larger with the smaller specific surface area of the activated carbon fibers and with the smaller particle diameter of the different-sized-activated carbon particles. The degree of packing of NFE in the pores of the activated carbon fibers was greater than that in the pores of the granular activated carbons. Copyright 2000 Academic Press.     

High-pressure DSC study on the hydriding and dehydriding of Mg/C nanocomposites

High-pressure DSC was applied to study the hydriding and dehydriding behavior of Mg 95 mass%–C 5 mass% composites, synthesized by ball milling with two different kinds of carbon additives (activated carbon derived from apricot stones AS and from bean pods BP) and magnesium with different particle sizes. The composites containing finer magnesium experience absorption capacity deterioration with hydriding/dehydriding cycling, but for the Mg–AS, this worsening is in lower degree compared to Mg–BP. The activated carbon derived from the AS, used for the composites preparation, has more pronounced positive effect on the hydrogen sorption characteristics of magnesium (with both finer and coarser particles), compared with the carbon derived from BP, due to its better protection of the Mg surface from oxidation and particles agglomeration during hydriding/dehydriding cycling.     

Fe-K/AC催化氧化脱硫剂制备及反应机理研究

采用正交实验法制备了负载铁、钾的活性炭(Fe-K/AC)热煤气催化氧化脱硫剂,考察了活性组分铁、钾含量、二价铁和三价铁比例、煅烧温度对催化氧化脱硫反应活性的影响。由正交实验极差分析可知,各因素影响程度依次为:钾含量>铁含量>煅烧温度> Fe²⁺/Fe³⁺,最优制备条件为,铁含量0.5%、钾含量5.0%、煅烧温度600 ℃、Fe²⁺/Fe³⁺比0.5。通过对脱硫剂的孔隙结构和表面形貌分析可知,活性炭表面负载的铁金属氧化物具有催化氧化硫化氢生成单质硫的活性,碱金属氧化物具有协同作用,可以改变表面酸碱性,促进硫化氢的催化转化,但过高的金属氧化物负载量会阻塞孔道,减小反应比表面积,从而降低脱硫剂的反应活性。     

炭在熔融碳酸盐中的直接电化学氧化性能

研究了活性炭粉在熔融碳酸盐中的直接电化学氧化性能. 通过线性扫描伏安曲线的测试发现, 将炭粉用酸处理, 碳酸盐中的炭含量、炭粒径、反应温度和反应气氛均会对活性炭的电化学氧化性能产生影响. 研究结果表明, 用HCl处理活性炭, 升高反应温度, 适当增加炭含量及炭粒子粒径和通入N2气均会提高活性炭的电化学氧化活性. 经HCl处理的、炭含量为15 g和炭粒径<100 μm的活性炭在850 ℃下、在N2气保护下和电位扫描速率为20 mV/s时的开路电位(OCP)为-1.40 V, 在-0.4 V下的电流密度可达到200 mA/cm2.     

Adsorption of phenol by oil-palm-shell activated carbons

Steam activated carbons from oil-palm shells were prepared and used in the adsorption of phenol. The activated carbon had a well-developed mesopore structure which accounted for 45% of the total pore volume. The BET surface area of the activated carbon was 1183 m²/g and a total pore volume of 0.69 cm³/g using N₂ adsorption at 77 K. The adsorption capacity of the activated carbon for phenol was 319 mg/g of adsorbent at 298 K. The adsorption isotherms could be described by both the Langmuir-Freundlich and the Langmuir equations. The adsorption kinetics consisted of a rapid initial uptake phase, followed by a slow approach to equilibrium. A new multipore model is proposed that takes into account of a concentration dependent surface diffusion coefficient within the particle. This model is an improvement to the traditional branched pore model. The theoretical concentration versus time curve generated by the proposed model fitted the experimental data for phenol adsorption reasonably well. Phenol adsorption tests were also carried out on a commercial activated carbon known as Calgon OLC Plus 12×30 and the agreement between these adsorption data and the proposed model was equally good.     

Magnetic mesoporous carbon for efficient removal of organic pollutants

Carbon materials such as activated carbons have been used in the field of water and wastewater treatments. However, the lack of mesopore and, particularly, the difficulty in recovering the spent carbon limited their applications. In this work, magnetic mesoporous carbon microspheres were synthesized by impregnating iron oxide precursors in the mesoporous carbon followed by the in situ conversion of the precursors into magnetite nanoparticles. The as-synthesized carbon microspheres with a high surface area of 742?m²/g and large mesopores of ～4.4?nm exhibited an excellent adsorption capacity for aqueous organic pollutants. The superparamagnetic microspheres with a saturation magnetization of 7.15 emu/g can be easily separated from the treated solution by external magnetic field.     

不同碳源合成Na2MnPO4F/C及其作为锂离子电池正极材料的性能

采用湿法球磨和原位热解碳包覆相结合的方法, 分别以硬脂酸、柠檬酸、聚乙二醇-6000 (PEG-6000)、β-环糊精为碳源, 制备了不同结构的Na₂MnPO₄F/C 复合材料, 并研究了它们作为锂离子电池正极材料的电化学行为. 通过X射线衍射(XRD)、扫描电镜(SEM)、BET比表面积测试、恒流充放电等表征手段, 比较和分析了产物的结构、形貌及电化学性能. 研究结果表明, 由不同碳源制备的材料在形貌和颗粒尺寸上有明显差异, 进而对它们的电化学性能造成很大影响. 影响电化学性能的关键因素在于材料一次颗粒的大小. 其中, 以柠檬酸为碳源制备的样品呈现出典型的微纳结构和最小的一次颗粒(10-40 nm). 并给出最佳的电化学性能: 在1.5-4.8 V电压范围内, 以5 mA·g^-1充放电电流获得的首次放电比容量约为80 mAh·g^-1, 且循环稳定性良好.     

电池正极材料Li3V2(PO4)3/C的水热合成和性能

以LiOH·H2O, NH4VO3, NH4H2PO4 和麦芽糖等为原料, 采用水热法合成了碳包覆的磷酸钒锂化合物, 考察了碳含量对材料电化学性能的影响. 利用XRD, TEM, SEM和恒流充放电测试等手段对产物的结构、 形貌和电化学性能进行表征. 结果表明, 在650℃煅烧的样品为单一纯相的单斜晶体结构. 晶体颗粒分布为100~300 nm, 粒度分散均匀, 分散性良好, 无团聚现象, 且在颗粒表面包覆了一层无定形碳, 这有利于改善材料的导电率. 含碳量为10.23%的样品, 在倍率1.0C的电流密度下, 在3.0~4.3 V电压范围内, 样品的首次放电比容量高达118.8 mA·h/g, 循环15圈后放电比容量为115.1 mA·h/g, 容量保持率为96.88%.     

Adsorption of some toxic elements from water samples on modified activated carbon,activated carbon and red soil using neutron activation analysis

A simple and sensitive method for the determination of some metalloids and heavy metals in water samples is presented. The method is based on the preconcentration of the attachment of chelating functionalities with metalloids and toxic metals irreversibly and targeted towards toxic metals adsorbed on modified activated carbon, activated carbon and red soil particles at pH 3.0–9.0±0.2, followed by quantitative determination using instrumental neutron activation analysis (INAA), on the absorbers. Attachment results from attraction that may be physical, chemical, electrical, or a combination of all three. The efficient removal of metalloids and toxic metals, especially arsenic, chromium and mercury is anticipated. The adsorption capacity of the chemically modified activated carbon materials was evaluated for the above mentioned metalloid and toxic metal ions in the presence of iron ions and simulated water samples. Red soil particles containing iron was utilized in the control of oxidation-reduction reaction with metalloids and toxic metals. The preconcentration of the elements of interest on red soil particles, activated carbon and modified activated carbon at different depths, pH and oxidation states was investigated. The results obtained showed good agreement with certified values giving relative errors of less than 10%.     

碳包覆LiFe0.5Co0.5PO4固溶体正极材料的制备及其电化学性能

分别以四水磷酸铁（FePO₄·4H₂O）和二水草酸亚铁（FeC₂O₄·2H₂O）为铁源,采用简单便捷的流变相法制备了碳包覆LiFe_0.5Co_0.5PO₄固溶体材料（LiFe_0.5Co_0.5PO₄/C,简称为LFCP/C）。采用X射线衍射（XRD）、扫描电镜（SEM）、透射电镜（TEM）、恒流充放电等测试手段对复合材料的物相、形貌结构和电化学性能进行了表征和测试。结果表明,2种铁源得到的材料均为橄榄石晶型结构且结晶度良好,二者在颗粒尺寸分布、碳包覆效果和电化学性能方面具有显著的差别。用作锂离子电池正极材料时,以FeC₂O₄·2H₂O为原料得到的LFCP/C具有更优异的电性能：在2.5~5.0 V电压范围内,0.1C倍率下（1C=150 mA·g^-1）,放电比容量为137.5 mAh·g^-1,在10C仍具有57.6 mAh·g^-1的放电比容量;0.5C循环100次后容量仍保持78.1%。该样品更佳的电化学性能主要得益于其更小的平均颗粒尺寸,更高的比表面积和理想的碳包覆效果。     

Carbon fiber microelectrodes modified with carbon nanotubes as a new support for immobilization of glucose oxidase

Carboxylated carbon nanotubes were coated onto carbon microfiber electrodes to create a micron-scale bioelectrode. This material has a high surface area and can serve as a support for immobilization of enzymes such as glucose oxidase. A typical carbon nanotube loading of 13???g?cm^?1 yields a coating thickness of 17???m and a 2000-fold increase in surface capacitance. The modified electrode was further coated with a biocatalytic hydrogel composed of a conductive redox polymer, glucose oxidase, and a crosslinker to create a glucose bioelectrode. The current density on oxidation of glucose is 16.6?mA?cm^?2 at 0.5?V (vs. Ag/AgCl) in oxygen-free glucose solution. We consider this approach to be useful for designing and characterizing surface treatments for carbon mats and papers by mimicking their local microenvironment.

Effects of particle size on the electrochemical performances of a layered double hydroxide, [Ni<Subscript>4</Subscript>Al(OH)<Subscript>10</Subscript>]NO<Subscript>3</Subscript>

In this paper, the electrochemical performances of a layered double hydroxide, [Ni₄Al(OH)₁₀]NO₃, of different particle sizes are studied. The results show that the particle size of the sample has evident effects on its discharge capacity at high current density, although a larger capacity may be observed for the bigger particles when they are discharged at lower current densities, e.g. 0.2 A g⁻¹. However, the capacity decreases more quickly than that of the sample in smaller particle size when the current density increases. For example, the discharge capacity of the smallest particle remains as high as 180 mAh·g⁻¹ even at very high current density, e.g. 4.0 A g⁻¹. The results also show that long time soaked electrodes in 7 mol l⁻¹ KOH have improved performance, especially for the hydrothermal samples. It also seems that there is an optimal size for materials, which can maintain their performance for longer time.     

Microstructure changes to iron nanoparticles during discharge/charge cycles

Iron nanoparticles that were synthesized by chemical reduction were used as the active material at the electrode, followed by measurement of their capacity during discharge/charge cycles. The discharge capacity of the first cycle was extremely high, 510 mAh/g-Fe, at a current density of 200 mA/g-Fe, indicating a marked increase in the capacity and the output current of iron electrodes when nanoparticles of iron, instead of micron-sized particles were used as the active materials. However, this capacity deteriorated rapidly during the discharge/charge cycles, while the size of iron nanoparticles increased, suggesting that the dissolution and re-crystallization of iron could have occurred during these cycles. A good correlation was found between the capacities and the surface areas of iron nanoparticles following each cycle. Our result further demonstrated that the capacity depends only on the surface area of iron particles, varying by 30 mAh with every 1 m² of iron.     

Application of response surface methodology for optimization of nano-TiO2 preparation using modified sol–gel method

Nano-sized TiO₂ was prepared using sol–gel process in microemulsion combining with solvent thermal technique. Response surface methodology was applied to optimize water/Triton X-100 molar ratio (w), n-hexanol/TX-100 molar ratio (m) and acetyl acetone/tetrabutyl titanate molar ratio (p) to influence the particle size (d), surface area (S), adsorptive capacity (G) and photocatalytic reaction rate (k). The relationship between responses (d, S, G and k) and preparation conditions (w, m and p) are followed second order polynomial equation and the coefficient is above 0.96. The smaller particle size, the bigger surface area it is accompanying the higher adsorption capacity and photocatalytic activity. The optimized experimental condition is w of 5.54, m of 7.41 and p of 0.44 with predicted particle size of 18.08 nm, surface area of 90.45 m²/g, adsorptive capacity of 9.63 mg/g and reaction rate of 0.12 min^?1.     

A New Approach for Controlling Mesoporosity in Activated Carbon by the Consecutive Process of Air Oxidation,Thermal Destruction of Surface Functional Groups,and Carbon Activation (the OTA Method)

A new and simple method, based entirely on a physical approach, was proposed to produce activated carbon from longan fruit seed with controlled mesoporosity. This method, referred to as the OTA, consisted of three consecutive steps of (1) air oxidation of initial microporous activated carbon of about 30% char burn-off to introduce oxygen surface functional groups, (2) the thermal destruction of the functional groups by heating the oxidized carbon in a nitrogen atmosphere at a high temperature to increase the surface reactivity due to increased surface defects by bond disruption, and (3) the final reactivation of the resulting carbon in carbon dioxide. The formation of mesopores was achieved through the enlargement of the original micropores after heat treatment via the CO₂ gasification, and at the same time new micropores were also produced, resulting in a larger increase in the percentage of mesopore volume and the total specific surface area, in comparison with the production of activated carbon by the conventional two-step activation method using the same activation time and temperature. For the activation temperatures of 850 and 900 °C and the activation time of up to 240 min, it was found that the porous properties of activated carbon increased with the increase in activation time and temperature for both preparation methods. A maximum volume of mesopores of 0.474 cm³/g, which accounts for 44.1% of the total pore volume, and a maximum BET surface area of 1773 m²/g was achieved using three cycles of the OTA method at the activation temperature of 850 °C and 60 min activation time for each preparation cycle. The two-step activation method yielded activated carbon with a maximum mesopore volume of 0.270 cm³/g (33.0% of total pore volume) and surface area of 1499 m²/g when the activation temperature of 900 °C and a comparable activation time of 240 min were employed. Production of activated carbon by the OTA method is superior to the two-step activation method for better and more precise control of mesopore development.     

Determination of surface ζ‐potential and isoelectric point of carbon surfaces using tracer particle suspensions

Carbon materials are widely used in a range of applications from biomaterials to sensing and electronics. Many of these applications rely on the ability to control carbon/water interfacial properties, in particular, surface charge density. This work reports a study of the electrokinetic properties of amorphous carbon thin films as a function of pH and surface chemistry. Surface ζ‐potential (SZP) and isoelectric point were determined using the tracer particle method. Initially, the use of sulfonated and amine‐terminated latex bead suspensions as tracer particles for the determination of SZP of reference polymer surfaces was validated. The tracer particle method was then applied to the determination of SZP and isoelectric point of macroscopic carbon surfaces with different surface chemistry. Highly graphitic and sp³‐rich hydrogenated carbon surfaces were found to display negative SZP, as expected for hydrophobic surfaces. The isoelectric point of the most highly graphitic surface was found to be pH_iso = 3.7. Surface oxidation of these films resulted in a decrease of SZP at all pH values and in a downshift of pH_iso to values lower than 1.5, consistently with the presence of surface acidic groups arising from oxidation. Results indicate that the specific choice of acid/base chemistry for the tracer particles does not significantly affect either SZP or pH_iso determinations. These results show that the tracer particle method in combination with widely available latex beads as tracers can be applied for the determination of carbon SZP as a function of pH. Copyright © 2017 John Wiley & Sons, Ltd.     

Synergistic effect of nitrogen and molybdenum on activated carbon matrix for selective adsorptive Desulfurization: Insights into surface chemistry modification

This study reports the synthesis of mesoporous metal-modified nitrogen doped activated carbon (AC-N-Mo) from date seeds by ZnCl₂ activation and its applicability for selective adsorptive desulfurization of dibenzothiophene (DBT). The AC-N-Mo exhibits higher adsorption capacity for DBT at 100 mg-S/L with the maximum removal percentage of 99.7 % corresponding to 19.94 mg-S/g at room temperature than the unmodified carbon with 17.96 mg-S/g despite its highest surface area and pore volume of 1027 m²g^?1 and 0.55 cm³g^?1 respectively. The adsorption capacity breakthrough follows the order AC-N-Mo > AC-Mo > AC > AC-N. Also, AC-N-Mo displays excellent selectivity in the presence of aromatics (toluene, naphthalene, and 1-methylisoquinoline). The enhancement in the DBT uptake capacities of AC-N-Mo is attributed to the synergistic effect of nitrogen heteroatom that aids the dispersion of molybdenum nanoparticles on carbon surface thereby improving its surface chemistry and promising textural characteristics. The kinetic studies showed that the DBT adsorption proceeds via pseudo-second order kinetics while the isotherm revealed that Langmuir fit the data more accurately for the adsorbents. The physical properties (surface area, pore volume, particle size, etc.) and chemical properties (carbon content, etc.) of as-prepared adsorbents namely; AC, AC-N, AC-N-Mo, and AC-Mo were characterized by N₂– physisorption, X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Spectroscopy/Energy Dispersive Spectroscopy (SEM/EDS), Raman Spectroscopy (RS), Fourier Transform Infrared Spectroscopy (FTIR) and Ammonia-Temperature-Programmed Desorption (NH₃-TPD).     

Potassium bromate modification of the granular activated carbon and its effect on nickel adsorption

Granular Activated Carbon (GAC), a commercial adsorbent for the removal of heavy metals was treated chemically with potassium bromate for it’s surface modification and it’s adsorption capacity was investigated with nickel ions. There was an increase in the adsorption capacity of the modified carbon by 90–95% in comparison to the raw granular activated carbon towards nickel ion adsorption. Potassium Bromate oxidation treatment was employed for a period of about 30 mins initially followed by 60 mins and the oxidized carbons were adsorbed with nickel ions. Metal sorption characteristics of as received and modified activated carbons were measured in batch experiments. Batch adsorption was successfully modeled by Langmuir Isotherm Model which indicates monolayer adsorption. The adsorption isotherms also fit well to the Freundlich Model. Effects of pH of initial solution, time of oxidation and mode of treatment on the adsorption process were studied. Experimental results showed that metal uptake increased with an increase in pH and oxidation time. The samples were characterized by Scanning Electron Microscope (SEM) studies and surface area analyzer.     

Effects of activation conditions on the structural and adsorption characteristics of pinecones derived activated carbons

This study was conducted to understand and optimize the activation process for the production of a low-cost activated carbon (AC) using a renewable and plentiful biomass waste, pinecones. This was achieved by tracking the changes in porous structure, surface chemistry and adsorption properties of the AC produced using different activating agents, activation temperatures, holding times and heating rates. Generally, produced ACs were predominantly microporous with small external surface area and were different in terms of H/C and O/C ratios. Study of Pb²⁺ cations adsorption on these samples proved the high affinity of the pinecones derived ACs to this cation. The best adsorption behaviour was recognized in sample prepared by impregnation with H₃PO₄ at weight ratio of 2, then heating at 400?°C for 2?h at 5?°C/min heating rate. This sample possessed the highest BET surface area (1335 m²/g). The adsorption process obeyed the pseudo-first-order and Freundlich model slightly better than the pseudo-second-order kinetics and Langmuir model. The high Langmuir maximum adsorption capacity of 418?mg/g supports the applicability of the produced AC for the removal of Pb²⁺ cations from wastewater.     

聚苯胺炭复合载体制备的钯催化剂对甲酸的电催化氧化

制备了导电高分子聚苯胺与活性炭的复合载体(PAnC),用PAnC作为载体制备的钯催化剂性能优于单独活性炭作为载体制备的催化剂。此外掺杂十二烷基磺酸钠制备的聚苯胺碳载体(PAnC-S)具有比PAnC更低的电荷传递电阻,10~25 nm的介孔数量明显增加,比表面积增大到94.9 m²/g。PAnC-S与PAnC粒径均匀,粒径均在30 nm左右。以PAnC-S和 PAnC为载体制备的钯催化剂比活性炭作载体制备的钯催化剂具有更大的电化学比表面积,分别为84.7和62.6 m²/g。对甲酸的氧化具有更高的电化学活性和稳定性。