碳纳米管氧化对水中微量异狄氏剂的吸附性能影响

碳纳米管表面经强酸氧化处理,管体发生解体,分散,形成碳纳米管胶体,用于去除水中低浓度持久性有机污染物异狄氏剂。扫描电镜观测表明,氧化后的碳纳米管团簇被分散开,碳纳米管被打断;红外光谱测试曲线表明,硝酸氧化后的碳纳米管表面引入了大量含氧官能团。氧化前后的碳纳米管对异狄氏剂的吸附实验研究表明,氧化后碳纳米管的吸附性能优于原始碳纳米管吸附性能,且等温吸附曲线均呈线性。     

Studies Relating to Removal of Arsenate by Electrochemical Coagulation: Optimization,Kinetics, Coagulant Characterization

The present investigation aims to remove arsenate [As(V)] by electrochemical coagulation using mild steel as anode and cathode. The results showed that the optimum removal efficiency of 98.6% was achieved at a current density of 0.2 A dm^?2, at a pH of 7.0. The effect of current density, solution pH, temperature, co-existing ions, adsorption isotherm, and kinetics has been studied. Kinetics reveals that the removal of arsenate by electrochemical coagulation is very rapid in the first 15 min and remains almost constant with the progress of reaction. The adsorption kinetics obeys the second-order rate expression. An equilibrium isotherm was measured experimentally and the results were analyzed by Langmuir, Freundlich, Dubinin- Redushkevich, and Frumkin using the linearized correlation co-efficient. The characteristics parameters for each isotherm were determined. The Langmuir adsorption isotherm was found to fit the equilibrium data for arsenate adsorption. Temperature studies showed that the adsorption was endothermic and spontaneous in nature.     

Kinetic and Thermodynamic Studies of the Adsorption of Several Anionic Dyes From Water Samples on Magnetite-Modified Multi-Walled Carbon Nanotubes

In this study magnetite-modified multi-walled carbon nanotubes (MMMCNTs) were used as an adsorbent for the removal of four anionic dyes from aqueous solutions. Batch studies were performed to address various experimental parameters for the removal of these dyes. Kinetic studies showed that the adsorption of dyes on MMMCNTs was almost a rapid process. Quasi equilibrium was reached in 45 min. Pseudo-first-order and pseudo-second-order models were applied to fit the experimental data and the results show that the adsorption of dyes followed the pseudo-second-order kinetic model. The thermodynamic analysis indicates an increase in the temperature resulted in increasing the dyes adsorption capacity of the adsorbent indicating the process to be endothermic.     

多壁碳纳米管氟化改性新方法研究

以聚四氟乙烯（PTFE）高温热解产生的含氟气体作为氟化剂与多壁碳纳米管（MWCNTs）反应制备了氟化多壁碳纳米管（F-MWCNTs）,并运用红外光谱（FTIR）、扫描电镜（SEM）、X-射线衍射（XRD）、接触角测试等手段对其进行了检测。结果显示,多壁碳纳米管表面有C-F键生成,样品结构未遭破坏且疏水性得到改善,取得了较好效果。与以氟气作氟化剂的传统方法相比,该方法操作更简单安全、成本更低,有望应用于工业化生产。     

碳纳米管吸附水体污染物的研究进展

碳纳米管是一种新型纳米材料,可分为单壁碳纳米管和多壁碳纳米管两种类型,具有独特的物理和化学性质,其应用研究已成为当前的研究热点。文章介绍了碳纳米管的结构和性质,综述了碳纳米管对水体中金属离子、无机非金属离子以及有机物脂肪烃、芳烃、胺、酚等物质的吸附研究进展,并展望了碳纳米管在吸附方面的应用前景。     

Cross-Linking of Multi-Walled Carbon Nanotubes with Polyethylene Glycol

In this paper a new approach to cross-link two individual multi-walled carbon nanotubes (MWCNTs) by a nucleophilic substitution of brominated MWCNTs using polyethylene glycol anion was introduced. The functionalized MWCNTs were characterized using thermogravimetric analysis (TGA), energy-dispersive X-ray (EDX) spectroscopy, transmission electron microscopy (TEM), and Fourier transform infrared (FT-IR) spectroscopy. It is found that polyethylene glycol act as cross-linking agents to interconnect or cross-link the MWCNTs within and among the bundles, as demonstrated by TEM analysis, and few defects will be induced to the nanotube sidewalls. After cross-linking of PEG, the functionalized MWCNTs are still insoluble in any solvent; however, the morphologies of the cross-linked MWCNTs were largely intact, undoubtedly which will provide a useful way to construct nanoscale devices with MWCNTs in the future.     

Effect of Dispersed Multi-Walled Carbon Nanotubes on Mixed Matrix Membrane for O2/N2 Separation

Mixed matrix membranes (MMMs) consisting of multiwalled carbon nanotubes (MWCNTs) embedded within polyetherimide were prepared. Surfactants of different charges were utilized to disperse the nanotubes through a simple non-covalent approach. The characterization results suggest that proper selection of the dispersing agent contributed to better dispersion of nanotubes. The MMMs exhibited improved thermal stability and mechanical strength, which indicate the improvement of dispersion and compatibility within the polymer matrix. The resulting membrane exhibited permeance improvement of O₂ and N₂ as much as 87.7% and 120% respectively compared to that of neat polyetherimide. The results implied that Triton-X100 treated MWCNTs is a promising filler to enhance gas permeability.     

Friedel盐对废水中低浓度Cd2+的吸附动力学

以合成的Friedel盐(FS, 3CaO×A12O3×CaCl2×10H2O)为吸附剂,研究了FS去除废水中Cd2+的反应动力学和等温吸附特性. 考察了FS盐用量、温度及Cd2+初始浓度对Cd2+去除的影响. 结果表明,FS用量为0.03 g/L时,在室温下对废水中初始浓度为10 mg/L的Cd2+的去除率大于94.34%,吸附容量可达301.9 mg/g,吸附主要以离子交换吸附为主,最终形成Cd4Al2(OH)12Cl2(H2O)4×xH2O及Cd4Al2(OH)12Cl2×4H2O化合物. 利用一级动力学模型关联了反应动力学数据,得到速率常数k=0.049 min-1,吸附行为较符合Langmuir等温吸附方程.     

Powdered Activated Carbon Separation from Water by Foam Flotation

Abstract

Powdered activated carbon was separated from dilute aqueous suspensions (200–1000 mg/L) by foam flotation using surfactants (anionic or cationic). The effects of surfactant type, pH value of the suspension, initial carbon and surfactant concentrations, flotation time, and air flow rate on the dispersed-air flotation of powdered activation carbon were investigated. In optimum conditions the powdered activated carbon separation was almost complete. The ζ-potential of powdered activated carbon was also measured in the presence and absence of surfactants. Finally, carbon flotation was examined after the carbon had adsorbed chromate ions from an acidic solution (pH 2). Almost complete separation of Cr(VI)-loaded carbon was obtained by using an anionic surfactant.     

多壁碳纳米管在水泥浆中的分散性

分别采用聚羧酸减水剂、聚乙烯吡咯烷酮（PVP）、洗衣粉（XYF）等3种表面活性剂并结合超声波分散方法,研究了多壁碳纳米管（MWCNTs）在水中和水泥浆中的分散性及其对水泥强度的影响,采用人工观察和扫描电子显微镜分别评价了MWCNTs在水中的分散性和在水泥硬化体中的分布情况。结果表明：单独采用减水剂为分散剂并在超声波分散条件下,MWCNTs在水中和水泥浆中容易发生团聚,无法起到增强作用;在超声波分散作用下,采用PVP和XYF为分散剂能够显著提高MWCNTs在水中和水泥浆中的分散性,PVP大幅度提高了水泥硬化体强度,但XYF却使强度大幅度降低,这是因其具有的较强起泡功能使水泥硬化体中的气泡量增加、气孔尺寸提高,并形成一些较大孔隙,从而显著降低了水泥石的密实性。     

Novel batch reactor design for the adsorption of arsenate on chitosan

BACKGROUND: The sorption of arsenate, a poison of acute toxicity found in natural waters, onto chitosan, a biosorbent derived from waste seafood shells has been studied. A batch adsorber design model was developed to determine how much chitosan adsorbent is required to reduce the arsenate concentration in solutions to the WHO standard of 10 µg L^?1. RESULTS: A series of batch kinetic experiments has been carried out at different initial pH values. The initial arsenate sorption appears to be completed after 30 min, however, a steady reversible reaction takes place resulting in the desorption of arsenate over 48 h. These phenomena in the batch kinetic data have been correlated simultaneously using the newly developed pseudo‐first order reversible model. Two batch reactor design models have been developed and compared. The first model is a conventional approach based on the equilibrium isotherm capacity equation. A second batch adsorption reactor design is based on the principle of contacting time required, t_max, for the chitosan to achieve its maximum adsorption capacity, q_max. The practical outcome from the second batch adsorber model results in a saving in adsorbent mass per batch of approximately 39.4%, 96.2% and 92.3% chitosan adsorbent at pH conditions of 3.5, 4.0 and 5.0, respectively. CONCLUSION: The adsorbent cost and handling costs are reduced in the second batch adsorber model. There is also a significant savings in the batch turnaround time required in the batch adsorber design when the design is based on the maximum adsorption capacity rather than the equilibrium adsorption capacity. Copyright © 2010 Society of Chemical Industry     

取向多壁碳纳米管的制备及其在染料敏化太阳能电池中的应用

使用经少量氯铂酸处理过的金属钛板作为基底,采用化学气相沉积法获得多壁碳纳米管。扫描电镜观察表明,经过氯铂酸处理过的钛板比未经过处理的钛板表面粗糙度低,获得的碳纳米管有一定取向性。将这种复合体系用作染料敏化太阳能电池的对电极,制作电池并测量其光电性能。与使用未经处理的多壁碳纳米管／钛板对电极的电池相比,使用经过氯铂酸处理...     

ABS/碳纳米管抗静电复合材料的制备与表征

通过微乳液聚合的方法将聚苯胺(PANI)接枝到酸化碳纳米管表面,再将原始碳纳米管、酸化碳纳米管、PANI接枝碳纳米管及纯PANI分别添加到丙烯腈-丁二烯-苯乙烯塑料(ABS)中。运用红外光谱、X射线衍射、透射电子显微镜对不同阶段的碳纳米管进行了表征;扫描电子显微镜观察发现,PANI接枝碳纳米管在ABS基体中的分散性优于原始碳纳米管;电性能结果表明,在相同添加量的情况下,PANI接枝碳纳米管与其他填料相比,抗静电效果最佳。     

卧式加压溶气泡沫分离水溶液中低含量蛋白质

以大豆蛋白为目标蛋白,蛋白水溶液为模拟体系,采用卧式加压溶气泡沫分离装置考察了原料液流量、pH值、溶气水流量等因素对蛋白质脱除率的影响,并根据其分子结构特征从过程工程视角分析了以卧式泡沫分离装置由水中去除的优势.结果表明,最佳操作条件为:原料液浓度8mg/L,原料液流量50L/h,pH值4.5,溶气水流量275L/h,该条件下水中蛋白质的脱除率可达90.5%.     

Greenhouse Gas Adsorptivity of Horn-Shaped Carbon Nanotubes over Nitrogen: Equilibrium Study

The synthesis of horn-shaped carbon nanotubes using carbon tetrachloride as carbon source was carried out by solvothermal method at 200°C for 2 h. The scanning and transmission electron microscopic characterization of the obtained product showed the formation of horn-shaped carbon nanotubes with irregular wall structure having inner diameter of ～105 nm and length of ～1 µm. The equilibrium gas adsorption properties of horn-shaped carbon nanotubes derived from carbon tetrachloride were successfully investigated for CO₂, CH₄, and N₂ at 288, 303, and 318 K. Horn-shaped carbon nanotubes possess better CO₂ adsorption capacity (2.53 mmol/g) with high capacity selectivity (14.7) and equilibrium selectivity (59.1) over N₂ at 288 K. The detailed adsorption study with estimation of physical parameters such as Henry's constant and heat of adsorption identifies the horn-shaped carbon nanotubes as a potential adsorbent material in the field of CO₂ storage and separation.     

Radial Corrugations of Multi-Walled Carbon Nanotubes Driven by Inter-Wall Nonbonding Interactions

We perform large-scale quasi-continuum simulations to determine the stable cross-sectional configurations of free-standing multi-walled carbon nanotubes (MWCNTs). We show that at an inter-wall spacing larger than the equilibrium distance set by the inter-wall van der Waals (vdW) interactions, the initial circular cross-sections of the MWCNTs are transformed into symmetric polygonal shapes or asymmetric water-drop-like shapes. Our simulations also show that removing several innermost walls causes even more drastic cross-sectional polygonization of the MWCNTs. The predicted cross-sectional configurations agree with prior experimental observations. We attribute the radial corrugations to the compressive stresses induced by the excessive inter-wall vdW energy release of the MWCNTs. The stable cross-sectional configurations provide fundamental guidance to the design of single MWCNT-based devices and shed lights on the mechanical control of electrical properties.     

Alpha-Cypermethrin Pesticide Adsorption on Carbon Aerogel and Xerogel

Carbon aerogel (CA) and xerogel (CX) are proposed for pesticide adsorption as new carbon adsorbent materials. These materials are prepared by polycondensation of resorcinol and formaldehyde in Na₂CO₃ catalysis, followed by a drying step, in CO₂ supercritical or normal conditions to obtain organic aerogel or xerogel, and a pyrolytic step to obtain CA or CX. Adsorption experiments were carried out in batch conditions under magnetic stirring. Adsorbent quantity and grain size, pH, and temperature, and alpha-cypermethrin concentration influence on the adsorption efficiency were considered. The optimum parameters were established to be as follows: 0.01 g adsorbent, d < 0.025 mm, and 318 K. In all cases, CA proved to be more efficient than CX for alpha-cypermethrin removal from water samples. Equilibrium (Langmuir and Freundlich isotherms), kinetics (pseudo-first- and pseudo-second-order, intra-particle diffusion, and liquid film diffusion models) and thermodynamics of the considered adsorption process were discussed in detail. Equilibrium was best described by the Langmuir isotherm, while the kinetic of the process was best described by the pseudo-second-order model. Thermodynamic parameters showed that alpha-cypermethrin adsorption is an endothermic process.