Light and Electron Microscopy Studies of the Visible Diffusion Zone of Mild Steel Pack Cyanided in Processed Cassava Leaves

This study investigates the microstructure of the processed cassava leaves. Standard parts machined from low visible diffusion zone formed in low carbon steel pack cyanided using carbon steel were pack cyanided by high temperature in-situ diffusion of nascent carbon and nitrogen into austenite. Formation of a visible diffusion zone was confirmed after observation with a Reichert-Jung Polyval optical microscope coupled with Zeiss AxioCam ICc 1 camera. High magnification Scanning Electron Microscope （SEM） imaging of the visible diffusion zone was done with a CamScan Series 2 scanning electron microscope. The zone was found variable in depth as measured from a representative position. The structure of all samples consists of ferrite and pearlite as determined by optical and SEM examination. Resulting products were thus both tough and hard suitable for service environments requiring high resistance to both wear and impact failure.     

A Tool for Interrogation of Macromolecular Structure

Our program BABELPDB allows browsing and interrogating the native and derived structural features of biomacromolecules using data obtained from the Protein Data Bank （PDB）. Major features of BABELPDB are： （1） convert from PDB to other formats, （2） add or remove H-atoms, （3） strip the crystallization water molecules and （4） separate the ct-carbons （Cα）. The co-ordinates obtained with BABELPDB permit characterizing the presence of H-bonds. The algorithm for detecting H-bonds is implemented in our program TOPO for the theoretical simulation of the molecular shape, An example is given to illustrate the capabilities of the software： the calculation of the fractal dimension of the lysozyme molecule with （1.908） and without （1.920） H-atoms. The figures compare well with reference calculations performed with our version of program GEPOL and results from Pfeifer et al. For proteins, Cα-skeleton extracted with BABELPDB allows drawing the ribbon image, which determines their secondary structure.     

Numerical Study of Solid Iron Carburization in a Carbon Monoxide Atmosphere

The diffusion step during the high temperature carburization of a spherical iron particle in a carbon monoxide atmosphere is mathematically modeled and numerically simulated in this work. The continuity equation is numerically solved using a forward finite-differences scheme, and a temperature range of 1,486-1,664 K is considered. An integration time during which the solid iron particle is not yet melted is assumed. The programming code was verified using experimental results previously reported by other authors. Radial carbon concentration is determined for several temperatures, and the average carbon concentration in the particle is obtained by numerical integration.     

ZnCl2活化茄子秸秆制备活性炭及表征

以茄子秸秆为原料、ZnCl2为活化剂制备活性炭。通过正交实验方法确定了制备活性炭的最佳工艺条件,采用低温氮气吸附、BET、Langmuir和BJH理论对其孔结构进行了表征,利用红外光谱分析样品的表面官能团,扫描电镜观察表面形貌。结果表明以茄杆活性炭的最佳工艺条件:浸渍比为2,浸渍时间为8h,活化温度为550℃,活化时间为60min,所得的活性炭的碘吸附值为1270.06mg/g,亚甲基蓝吸附值为17.4mL/g;BET和Langmuir比表面积分别为1649.615和1851.649m2/g,吸附总孔容为0.488cm3/g,吸附平均孔径为2.241nm。     

Experimental Investigations of Hot Forging Die Surface Layer of Skd61 Steel in Die Sinking Electrical Discharge Machining

Electrical discharge machining is an important manufacturing process for tool mould and die industries. The results of the research about EDM show that the performance of die sink reduced due to a change in the material quality of the surface layer than the base material. The article presents the result of the study on the hot forging die surface layer of the SKD61 hot die steel （surface roughness, surface microscopic hardness, microscopic structure of the surface layer, EDS analysis of the surface layer） after die sinking electrical discharge machining using a tool of titanium and copper in oil dielectric.     

Construction of the composites of nitrogen and sulfur-doped porous carbon and layered double hydroxides and the synergistic removal of heavy metal pollutants

Layered double hydroxides (LDHs) composites (NSPC@LDH) were successfully prepared on nitrogen and sulfur-doped porous carbon (NSPC) by a simple co-precipitation method. The synergistic effect between the modified porous carbon and LDH enhanced its adsorption performance. Compared with pure LDH, the composite had a larger specific surface area (188.78 m²/g) and pore structure with a smaller crystallite size (4.56 nm). The porous carbon carrier effectively mitigated the aggregation effect of LDH. The maximum adsorption capacities of NSPC@LDH for Zn²⁺ (100 ppm) and Cu²⁺ (100 ppm) were 125.7 mg/g and 137.5 mg/g, respectively, which were 2.85 and 2.39 times the original LDH. The XRD and XPS studies of the adsorbent after adsorption revealed that surface complexation and physical adsorption played a dominant role in the removal of Zn²⁺ and Cu²⁺, and the introduction of N, S heteroatoms provided more active centers for heavy metal ions. Moreover, after five desorption cycles, NSPC@LDH still exhibited high removal efficiency. The results indicated that the synthesized NSPC@LDH composites have great potential for removing Zn²⁺ and Cu²⁺ from aqueous solutions.     

Porous Silicon： Volume-Specific Surface Area Determination from AFM Measurement Data

Porous silicon layers manufactured by using （100）, 1-5 ohm-cm p-type （boron doped） wafer by electrochemical etching in HF etanol solution. Photoluminescence （PL） spectra of anodically etched silicon obtained for different conditions studied and surface characteristics are investigated by AFM. This study gives a simple way to determine specific surface are of porous silicon which plays a major role with porosity for explaining the blue shift in photoluminescence peak. Properties such as specific surface area, pore size, and pore size distribution, the main surface properties of layer are investigated from AFM data which are important material characteristics in many processing applications. The ＂specific surface area＂ （Sspecific） generally defined as the area of solid surface per unit mass of material, solid volume or cross section area. From 3-D reconstructions of AFM data, the surface area and the volume of the porous layer can be estimated directly and volume-surface specific area is calculated. For porous silicon this feature can be defined as the total surface area per volume and given by the unit m2/cm3. The method is simple not need to construct a special set up for measurement and non destructive.     

Application of Ceramic Membranes for Regeneration of Detergent Cleaning Solutions

Pressure-driven membrane processes were investigated for the recovery of contaminated cleaning solutions （a single-phase detergent） emanating from a diary industry. The experiments were performed in a semi-pilot membrane installation in cross-flow regime. The filtration tests were carded out using tubular ceramic modules differing in cut-offvalue, with high resistance to chemical agents. The effect of long term filtration time and process conditions （transmembrane pressure, cross-flow velocity and temperature） on transport and separation properties of the modules was evaluated. The usefulness of ceramic modules for regeneration of a single-phase detergent for the purpose of its reuse in cleaning systems was revealed. The modules in a long-term filtration regime, due to their hydrophilic nature, were characterized by relatively low susceptibility to fouling. Rinsing modules with deionized water after filtration experiments helped significantly to restore their original permeability or cause even an increase of water flux in comparison with the stream of deionized water. The recovered spent detergent maintained its basic cleaning properties, i.e., high pH, high concentration of NaOH and low value of surface tension. Moreover, the ceramic modules showed high retention of specific milk components （protein and lactose） and organic matter expressed as chemical oxygen demand （COD）. It has been shown that the transport and separation properties of the modules were dependent on the process parameters, such as transmembrane pressure, cross-flow velocity and temperature.     

Acid Activation of Kulantau Vermiculite

Adsorptive properties of laminated material with widening structural cell are determined by dispersion, which is depends on crystalline vermiculite grid structure. Created sorbents developed porous by acid activation desirable choice minerals with an expanding structural cell. Significant role in the formation of advanced sorbent porosity is the formation of thin layers of amorphous phase between partial destruction of the elements of the original structure of vermiculite.     

Equilibrium and kinetic studies of copper adsorption by activated carbon

Copper adsorption by granular activated carbon is reported in this paper. The experimental section includes titrations of activated carbon, as well as equilibrium and kinetic studies of copper adsorption. The potentiometric titration results show that the point of zero charge is 9.5, and that the surface charge increases with decreasing pH. The adsorption of copper strongly depends on solution pH and increases from 10 to 95% at pH ranging from 2.3 to 8. A dramatic increase in pH and emission of small gas bubbles are observed during the experiments, which may result from adsorption of hydrogen ion and/or reduction-oxidation reactions. The two-pK triple-layer model is employed to describe copper adsorption. KINEQL, an adsorption kinetics algorithm, is used to represent the experimental data, and it is found that the model can describe reasonably well the experimental measurements of surface charge, adsorption equilibrium, and adsorption kinetics. Calculations show that formation of the surface-metal complexes SO⁻Cu²⁺ and SO⁻CuOH⁺ (a hydrolysis product of SO⁻Cu ²⁺) in the outer layer around the surface of carbon results in removal of copper ion. It is also found that mass transfer controls the adsorption rate, and that adsorption occurs in the micropore region where both external mass transfer and diffusion are important.     

SiO2/SnO2复合凝胶对丙酮和氨气的吸附动力学研究

应用溶胶－凝胶法制备了SiO2/SnO2复合凝胶，测定了红外光谱，采用静态吸附法测定了不同组成的SiO2/SnO2复合凝胶对丙酮气体和氨气的吸附动力学曲线。结果表明，SiO2与SnO2凝胶的复合有利于气体的吸附，在凝胶中含有一定的羟基是吸附性强的根源。数据拟合得到的吸附动力学方程分别为x=c1(1-exp(-c2t)和x=c′1t/(1 c2′t)的形式，说明SiO2/SnO2复合凝胶对丙酮气体和氨气的吸附机理分别具有单活性位和双活性位吸附特征。     

Noncovalent functionalization of carbon nanotubes with porphyrins: meso-tetraphenylporphine and its transition metal complexes

Noncovalent functionalization of carbon nanotubes with meso-tetraphenylporphine (H2TPP) and its metal(II) complexes NiTPP and CoTPP was studied by means of different experimental techniques and theoretical calculations. As follows from the experimental adsorption curves, free H2TPP ligand exhibits the strongest adsorption of three porphyrins tested, followed by CoTPP and NiTPP. At the highest porphyrin concentrations studied, the adsorption at multi-walled carbon nanotubes was about 2% (by weight) for H2TPP, 1% for CoTPP, and 0.5% for NiTPP. Transmission electron microscopy observations revealed carbon nanotubes with a variable degree of surface coverage with porphyrin molecules. According to scanning electron microscopy, the nanotubes glue together rather than debundle; apparently, a large porphyrin excess resulting in polymolecular adsorption is essential for exfoliation/debundling of the nanotube ropes. The nanotube/porphyrins hybrids were studied by infrared and Raman spectroscopy, as well as by scanning tunneling microscopy. Electronic structure calculations were performed at the B3LYP/LANL2MB theoretical level with the unsubstituted porphine (H2P) and its Co(II) complex, on one hand, and open-end armchair (5,5) (ANT) and zigzag (8,0) (ZNT) SWNT models, on the other hand. The interaction of H2P with ANT was found to be by 3.9 kcal mol(-1) stronger than that of CoP. At the same time, CoP+ZNT complex is more stable by 42.7 kcal mol(-1) as compared to H2P+ZNT According to these calculated results, the free porphyrins interact less selectively with zigzag and armchair (i.e., semiconducting and metallic) nanotubes, whereas the difference becomes very large for the metal porphyrins. HOMO-LUMO structure, electrostatic potential and spin density distribution for the paramagnetic cobalt(II) complexes were analyzed.     

H2O2活化聚酰亚胺碳纳米纤维无纺布及其储电性能

聚酰亚胺碳纳米纤维无纺布经双氧水在氮气氛中750℃活化,使其比表面积增大,从而改善其储电性能.通过透射电镜观察活性碳纳米纤维的尺寸、形貌和结构;采用次甲基蓝水溶液吸附法测定活化碳纳米纤维的比表面积;用CHI660B电化学工作站测定该活性碳纳米纤维电极的储电性能.结果显示：活化后碳纳米纤维具有更大的比表面积,表面粗糙,电极材料的储电性能随活化程度的提高而增大;聚酰亚胺碳纳米纤维电极具有良好的超级电容器特性,在1 mol/L的H2SO4电解液中,经6 h活化后的碳纳米纤维电极具有良好的电荷储存能力,比电容量达到174.2 F/g.     

Adsorption of dimethyl methylphosphonate on metal impregnated carbons under static conditions

Active carbon, grade 80 CTC, of surface area 1199m(2)/g, 12x30 BSS particle size and coconut shell origin was impregnated (5%, W/W) with various impregnants such as Cu(II) 1,1,1,5,5,5-hexafluoroacetylacetonate, Cu(II) 1,1,1-trifluoroacetylacetonate, 1-phenylbute-1,3-dione-2-oxime plus Cu(II) using incipient wetness technique. These impregnated carbons along with active carbon (Grade 80 CTC) and whetlerite were studied for the adsorption of dimethyl methylphosphonate (DMMP) at 33+/-1 degrees C under static conditions. Cu(II) 1,1,1,5,5,5-hexafluoroacetylacetonate impregnated carbon system showed highest uptake (68.5%, W/W) of DMMP amongst all the carbon systems, however, active carbon with higher surface area could adsorb 61.5% (W/W) of DMMP under same conditions. It indicated that the adsorption by Cu(II) 1,1,1,5,5,5-hexafluoroacetylacetonate impregnated carbon was not only due to physisorption but chemisorption as well. Kinetics of adsorption was also studied and various parameters such as equilibration time, equilibration capacity, rate constant (k), diffusional exponent (n) and constant (K) were determined. Carbons with and without DMMP exposure were also studied using IR and TGA techniques. Reaction products were analyzed using gas chromatography coupled with mass spectrometry (GC/MS) and found to be methyl methylphosphonic acid (MMPA) and methylphosphonic acid (MPA) for Cu(II) 1,1,1,5,5,5-hexafluoroacetylacetonate impregnated carbon.     

全组分木质活性炭球的制备及其乙烯吸附性能研究

目的 制备全组分木质活性炭球,应用于乙烯吸附,筛选出乙烯吸附效果最好的活性炭球制备工艺。方法 以木材液化物为原料,探究不同的固化时间对制备的全组分木质活性炭球微观形貌的影响,利用场发射扫描电子显微镜观察其微观结构,通过氮气吸附-解析等温线计算样品孔径分布及其比表面积;使用气相色谱仪,结合乙烯吸附标准曲线,分析时间及吸附剂用量对4种活性炭球吸附乙烯性能的影响。结果 随着固化时间的增加,碳球表面趋于光滑、内部结构越来越致密,石墨化程度逐渐提高,比表面积和孔容逐渐减小。当固化时间为0.5 h时,比表面积高达2 073 m²/g,乙烯吸附量高达197.99 mg/g,约3 h达到吸附平衡。结论 全组分木质活性炭球能有效吸附乙烯气体,固化时间太长,活性炭球内部孔隙减少,不利于吸附乙烯气体。活性炭球孔容越大,乙烯吸附效果越好。     

用稻壳制备亚甲基蓝高吸附容量的超高比表面积活性炭

活性炭因具有高比表面积和丰富的孔结构而被广泛应用于吸附水处理中的污染物。稻壳具有独特的组成和微观结构, 是制备活性炭的优质碳源。以稻壳为原料, 利用过饱和KOH溶液的预活化和活化双重作用, 在不同温度下制备出超高比表面积活性炭。随着活化温度的升高, 活性炭的比表面积和总孔容逐渐增大。900 ℃下制得的活性炭具有超高比表面积, 达到3600 m²/g, 总孔容为3.164 cm³/g, 明显优于商用活性炭(YP-80, 比表面积为1310 m²/g, 总孔容为0.816 cm³/g)。具有最高比表面积的稻壳活性炭对亚甲基蓝的最大吸附量达到983 mg/g, 几乎是YP-80 (525 mg/g)的两倍。通过吸附动力学拟合, 吸附亚甲基蓝的过程与拟二级动力学模型一致, 表明该过程为化学吸附。     

Novel carbon felt composites with pyrocarbon deposited on carbon fiber: Hierarchical microstructure for improved phenol-adsorption

Carbon felt composites were prepared by chemical vapor deposition (CVD) method using Ni(NO₃)₂ as a catalyst and methane as a pyrocarbon precursor. The pyrocarbon which has been deposited on fiber surface increased gradually with increase in deposition temperature. Besides, the surface of the deposited pyrocarbon was seen to contain many micropores. The phenol-adsorption capability evaluation of the composites showed that the adsorption equilibrium was achieved in 90 min, and the maximum adsorption quantity reached was 13.37 mg/g. The Langmuir isotherm model was preferred in fitting the adsorption data compared with the Freundilch isotherm model. The theoretical maximum adsorption was calculated to be 17.45 mg/g. At pH = 5, the adsorption quantity was a minimum of 10.66 mg/g. Moreover, the phenol-adsorption quantity increased with increasing deposition temperature. The adsorption quantity on carbon felt composites without pyrolytic carbon deposition was minimum, being 9.11 mg/g, while that of carbon fiber produced at 950°C reached the maximum of 13.37 mg/g.     

A method for preparing ferric activated carbon composites adsorbents to remove arsenic from drinking water

Iron oxide/activated carbon (FeO/AC) composite adsorbent material, which was used to modify the coal-based activated carbon (AC) 12 x 40, was prepared by the special ferric oxide microcrystal in this study. This composite can be used as the adsorbent to remove arsenic from drinking water, and Langmuir isotherm adsorption equation well describes the experimental adsorption isotherms. Then, the arsenic desorption can subsequently be separated from the medium by using a 1% aqueous NaOH solution. The apparent characters and physical chemistry performances of FeO/AC composite were investigated by X-ray diffraction (XRD), nitrogen adsorption, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Batch and column adsorption experiments were carried out to investigate and compare the arsenic removal capability of the prepared FeO/AC composite material and virgin activated carbon. It can be concluded that: (1) the main phase present in this composite are magnetite (Fe(3)O(4)), maghemite (gamma-Fe(2)O(3)), hematite (alpha-Fe(2)O(3)) and goethite (alpha-FeO(OH)); (2) the presence of iron oxides did not significantly affect the surface area or the pore structure of the activated carbon; (3) the comparisons between the adsorption isotherms of arsenic from aqueous solution onto the composite and virgin activated carbon showed that the FeO/AC composite behave an excellent capacity of adsorption arsenic than the virgin activated carbon; (4) column adsorption experiments with FeO/AC composite adsorbent showed that the arsenic could be removed to below 0.01 mg/L within 1250 mL empty bed volume when influent concentration was 0.5mg/L.     

Removal of nickel ions from water by multi-walled carbon nanotubes

Multi-walled carbon nanotubes (MWCNTs) were produced by chemical vapor decomposition using acetylene gas in the presence of Ferrocene catalyst at 800 degrees C, and then oxidized with concentrated nitric acid at 150 degrees C. Both (as-produced and oxidized) CNTs were characterized by TEM, Boehm titration, N2-BET and cation exchange capacity techniques. The adsorption capacity for nickel ions from aqueous solutions increased significantly onto the surface of the oxidized CNTs compared to that on the as-produced CNTs. The effects of adsorption time, solution pH and initial nickel ions concentrations on the adsorption uptake of Ni2+ for both the as-produced and oxidized CNTs were investigated at room temperature. Both Langmuir and Freundlich isotherm models match the experimental data very well. According to the Langmuir model the maximum nickel ions adsorption uptake onto the as-produced and oxidized CNTs were determined as 18.083 and 49.261 mg/g, respectively. Our results showed that CNTs can be used as an effective Ni2+ adsorbent due to the high adsorption capacity as well as the short adsorption time needed to achieve equilibrium.     

掺氮多孔碳在二氧化碳吸附分离中的应用

CO₂作为温室气体, 其捕集和存储有着重要的现实意义。多孔碳材料掺杂N原子后可以极大地改变材料的表面化学性质, 增强表面碱性, 在CO₂吸附领域具有广泛的应用。基于N掺杂最新研究进展, 本文系统地介绍了原位、后处理等掺N方法和不同孔道结构对CO₂吸附分离或扩散传质的影响, 总结归纳了材料的物理结构参数、表面化学性质与CO₂吸附分离性能的关系, 指出了各种制备方法存在的问题及解决的方法, 为高性能的CO₂吸附剂的定向设计、制备以及工业化提供了理论参考。