用载钛改性活性炭纤维电极电吸附水中Cr(Ⅵ)

以溶胶-凝胶法制备TiO_2凝胶并涂敷在活性炭纤维表面,经高温处理后制得载钛改性活性炭纤维电极(TiO_2/ACF)。研究了TiO_2/ACF从废水中电吸附Cr(Ⅵ)的性能及吸附平衡后的再生,利用FT-IR、XRD和SEM对TiO_2/ACF材料表面进行表征。结果表明:在模拟废水pH=2.0、初始Cr(Ⅵ)质量浓度10 mg/L、电极电位0.6 V、极板间距9 mm、极板面积100 cm~2条件下,TiO_2/ACF对Cr(Ⅵ)的吸附效果最佳,吸附率接近100%,明显高于开路状态下的吸附率;活性炭纤维呈束状结构,其表面和束间分散有较多颗粒物,出现锐钛矿和金红石晶相,表明钛成功负载,其对Cr(Ⅵ)的吸附性能得以增强。     

高炉渣对铬离子的吸附特性研究

采用振荡吸附试验,研究了高炉渣用量、粒度、溶液pH值、吸附时间、溶液初始浓度等因素对去除Cr3 效果的影响。结果表明:高炉渣对溶液中的Cr3 有较强的吸附作用,按铬与高炉渣质量比为1:400投加高炉渣,铬的去除率达到97%以上,完全达到污水综合排放标准。在废水pH值4-12范围内高炉渣能够很好地适应Cr3 初始浓度的变化,对吸附去除Cr3 保持较高而稳定的吸附去除率。由于高炉渣表面带负电,而Cr(Ⅵ)是以阴离子团存在,故其对Cr(Ⅵ)的吸附去除能力远远低于Cr3 的吸附去除能力。     

TiCl_4-AlCl_3水解制备金红石TiO_2对Cr(Ⅵ)吸附研究

为研究金红石TiO_2对Cr(Ⅵ)的吸附,利用TiCl_4-AlCl_3水解制备球形的金红石TiO_2颗粒.在金红石TiO_2对Cr(Ⅵ)的吸附实验中,研究了时间、pH和Cr(Ⅵ)初始浓度对吸附的影响.利用伪一级、二级动力学模型和Webber-Morris模型对吸附动力学数据进行分析,并计算吸附过程的△G0,探究该吸附过程的机理.结果表明:金红石TiO_2对Cr(Ⅵ)的吸附平衡时间约为30 min,适宜的吸附pH值为5,平衡吸附容量随Cr(Ⅵ)初始浓度的增加而增加,当Cr(Ⅵ)浓度为800 mg/L时,吸附容量达到24.38 mg/g.吸附动力学更符合伪二级动力学模型,△Gθ的计算值为-5.679 kJ/mol,表明吸附过程为自发的化学反应过程. Webber-Morris模型拟合结果表明,金红石TiO_2对Cr(Ⅵ)的吸附主要以颗粒表面吸附为主.     

粉煤灰活性炭吸附含Cr废水试验研究

利用电厂粉煤灰可制备出具有较高吸附性能的粉煤灰活性炭.研究了不同pH值、投加量、时间、温度、溶液浓度、脱附方法条件下粉煤灰活性炭对Cr(Ⅵ)吸附性能的影响.结果表明,吸附反应为吸热过程;当粉煤灰活性炭掺入比为1∶250、pH值为2、25℃恒温振荡120 min时,粉煤灰活性炭最大吸附容量能达到4.67 mg/g;Cr饱和的粉煤灰活性炭,用0.05 mol/L浓度的NaOH脱附效果最佳,脱附率为129%.废弃印刷线路板湿式处理工艺中产生的废水,含Cr(Ⅵ)0.62 mg/L,在上述条件下,Cr(Ⅵ)去除率达95.16%;若在自然pH条件下,Cr(Ⅵ)的去除率能达到91.94%,均符合污水综合排放标准.粉煤灰活性炭用于含金属废水的处理有着广阔的应用前景.     

壳聚糖/磁性甘蔗渣生物炭复合材料对Cr(Ⅵ)的吸附特性

研究了壳聚糖/磁性甘蔗渣生物炭复合材料的制备及从模拟废水中吸附Cr(Ⅵ),采用SEM、FTIR、BET法对普通甘蔗渣和复合材料的结构进行表征。结果表明:壳聚糖/磁性甘蔗渣生物炭复合材料为团状结构,表面有大量微孔,并有许多孔隙穿插其中,化学结构较普通甘蔗渣有较大改变;在废水Cr(Ⅵ)初始质量浓度50 mg/L、废水pH=2、反应温度25℃、复合材料投加量8 g/L、吸附时间12 h条件下,Cr(Ⅵ)吸附去除率为98.7%,最大吸附量为8.779 6 mg/g;Langmuir等温吸附模型能反映吸附过程,吸附以单层吸附为主可用准二级动力学方程描述,吸附分快速吸附与慢速吸附2个阶段。     

用聚吡咯改性电解锰渣去除废水中的六价铬

研究了用聚吡咯(PPY)改性电解锰渣(EM R)制备吸附材料EM R-PPY并用以从废水中吸附去除Cr(Ⅵ),考察了吸附时间、初始Cr(Ⅵ)质量浓度、吸附剂加入量、溶液pH对EMR-PPY吸附去除Cr(Ⅵ)的影响,探讨了吸附过程的动力学和热力学.结果表明:在废水pH=2.0、EMR-PPY加入量1 g/L、初始Cr(Ⅵ)质量浓度150 mg/L条件下,Cr(Ⅵ)去除率达99.6％;吸附过程符合准二级动力学模型和Langmuir等温吸附模型,平衡状态下,理论最大吸附量为269 mg/g;吸附机制主要包括Cr2 O2-7与N+之间的静电作用、对Cr(Ⅵ)的还原作用、Cr2 O2-7与Cl-之间的离子交换作用;3次循环再生后,EMR-PPY对Cr(Ⅵ)的吸附量仍保持在100 mg/g以上,仍可继续使用.     

纳米ZnO的制备及吸附溶液中U(Ⅵ)的性能研究

研究了以尿素作沉淀剂,十二烷基硫酸钠作表面活性剂,采用均匀沉淀法制备纳米ZnO并采用静态试验法研究纳米ZnO吸附溶液中U(Ⅵ)的性能,考察了溶液pH、固液质量体积比、反应温度、接触时间和U(Ⅵ)初始质量浓度对纳米ZnO吸附溶液中U(Ⅵ)的影响。结果表明:纳米ZnO对溶液中的U(Ⅵ)有较好的吸附效果;室温下,纳米ZnO吸附U(Ⅵ)的最佳条件为溶液pH=6.0,接触时间80min,固液质量体积比0.5g/L,U(Ⅵ)初始质量浓度30mg/L;最佳条件下,纳米ZnO对U(Ⅵ)的吸附率达(96.32±1.47)%,吸附量为(57.79±0.89)mg/g,其吸附行为符合Freundlich和Temkin等温吸附模型,吸附机制为不均匀多层吸附为主、表面单层吸附为辅。     

对羟基苯甲酸存在下TiO2粉末光催化还原Cr(Ⅵ)的动力学研究

研究了对羟基苯甲酸存在下TiO2光催化还原Cr(Ⅵ)过程中不同对羟基苯甲酸浓度、Cr(Ⅵ)初始浓度及溶液初始pH值对Cr(Ⅵ)光降解速率的影响，认为TiO2悬浮体系能有效地光催化还原水溶液中的Cr(Ⅵ)离子，并得出TiO2光催化还原Cr(Ⅵ)过程符合L—H动力学模型。反应体系中的Cr(Ⅵ)初始浓度及初始pH值对TiO2光催化还原Cr(Ⅵ)过程的速率有较大的影响。酸性条件有利于Cr(Ⅵ)的光催化还原。对羟基苯甲酸具有芳香族化合物的特殊结构，对TiO2光催化还原Cr(Ⅵ)过程有显著的促进作用。     

钢渣负载羟基磷灰石复合材料对水溶液中铀的去除性能

采用溶胶—凝胶法制备出钢渣负载羟基磷灰石复合材料,并通过静态试验方法探讨pH、复合材料投加量、反应时间及铀初始浓度对复合材料吸附水溶液中U(Ⅵ)的影响。结果表明,复合材料对U(Ⅵ)具有较好的去除性能,在pH=4、投加量0.4g、反应时间120min的条件下,对初始浓度5mg/L的水溶液中U(Ⅵ)的去除接近完全,对应吸附量为1.25mg/g。复合材料对U(Ⅵ)的吸附过程为化学吸附,符合准二级动力学模型(R~2=0.996 9);Langmuir吸附等温线模型拟合(R~2=0.999 1)表明,吸附过程为吸附剂表面上的单层吸附;且通过R_L(R_L 0.063)的计算表明,复合材料对U(Ⅵ)的吸附极其接近不可逆吸附。     

零价纳米铁批处理水中Cr(Ⅵ)的研究

[目的]研究纳米零价铁(NZⅥ)对水中Cr(Ⅵ)的脱除效果及影响Cr(Ⅵ)脱除的主要因素.[方法]以Cr(Ⅵ)为研究对象,采用NaBH<,4>液相还原Fe<'3+>制备纳米级零价铁(NZVI),分析了0.01、0.03、0.04、0.05、0.07 g的NZVI对初始浓度为10.0、20.0、30.0、50.0、70.0 mg/L,温度分别为15、20、25、30、40℃,pH分别为3、5、7、8、9条件下的Cr(Ⅵ)去除率的影响.[结果]纳米零价铁可在极低投加量下有效去除溶液中Cr(Ⅵ),在25℃、pH为5、常压、恒温振荡器转速200 r/min、NZVI加入量0.05 g/100 ml的条件下,水体中20 mg/LCr(Ⅵ)的去除率大于90%.[结论]纳米零价铁能快速去除水体中Cr(Ⅵ),溶液pH,Cr(Ⅵ)初始浓度,温度,投加量等是影响Cr(Ⅵ)脱除的主要因素.     

含氮有机物对活性碳纤维还原吸附银的影响

用H3PO4、ZnCl2等活化剂分别制备了两种化学活化的活性碳纤维（HPSACF和ZCSACF）,并通过水蒸汽活化制备了水蒸气活化活性碳纤维（SACF）。研究了它们对水溶液中Ag(NH3)2^ 的还原吸附性能,并与活性碳（AC）的还原吸附进行了比较。不同方法制备的活性碳纤维（ACF）对Ag(NH3)2^ 的还原吸附能力有显著的差异,以磷酸活化法制备的ACF的还原能力最强,而AC有一定的还原吸附能力。含氮有机物的吸附对活性碳纤维或活性碳的还原吸附能力有很大的影响,一般而言,吸附至碳吸附剂上的对硝基苯酚和苯胺可促进AC、SACF和HPSACF的还原能力,且苯胺的促进作用大于硝基苯酚的促进作用。     

Sulfur Impregnation on Activated Carbon Fibers through H2S Oxidation for Vapor Phase Mercury Removal

Sulfur was impregnated onto activated carbon fibers (ACFs) through H2S oxidation catalyzed by the sorbent surface in a fixed-bed reactor. By changing the temperature and duration of the sulfur impregnation process, ACFs with different sulfur contents were developed. Characterization of ACFs before and after sulfur impregnation was conducted by surface area analysis, energy dispersive X-ray analysis, thermogravimetric analysis, X-ray photoelectron spectroscopy, and temperature programmed desorption. Vapor phase mercury adsorption experiments were carried out in a fixed-bed reactor. Sulfur was impregnated mainly as elemental sulfur and the amount of sulfur deposited on the ACF increased with an increase in impregnation temperature. Higher temperature leads to more uniform sulfur distribution inside the sorbent pores. The impregnation process can be explained by a combination of pore filling and monolayer adsorption, with the former mechanism predominating at low temperatures. In the absence of sulfur, the mercury adsorption capacity can be correlated with surface area and pore volume.     

Bending behavior of carbon nanotube-reinforced composites

The multi-scale modeling method was utilized to study the bending characteristics of a carbon nanotube (CNT) and CNT-reinforced composites.Through combining molecular dynamics and continuum mechanics,the tensional and flexural modulus of a CNT were calculated by a finite element model constructed by reticulate beams with solid cylinder shape and energy equal to C-C bonds.Then,another beam element with hollow cylinder shape and equivalent stiffness was utilized in place of a CNT in a matrix,thus,a multi-scale representative volume element (RVE) model of CNT-reinforced composite was established.Using this RVE model,the bending behavior of CNT-based composites Was analyzed.The influence of diameter D,length L,aspect ratio L/D,volume fraction,chiral of CNTs and shape of RVE as well as the arrangement of CNTs in matrix on the rein-forcement effect of flexural modulus of resultant nanocomposites were further discussed.The obtained data provide useful information for the design of CNT-reinforced composites.     

Improvement of Wear Resistance in Alumina Matrix Composites Reinforced with Carbon Nanotubes

Alumina matrix composites reinforced with carbon nanotubes (CNTs) fabricated by CNT purification, mixing, compaction, and sintering processes, and the effects of the CNT addition on wear resistance were investigated in relation to the relative density, hardness, and fracture toughness. Wear resistance and fracture toughness were measured by the dry sliding wear test method and the indentation fracture test method, respectively. Zero to ~3 vol pct of CNTs were homogeneously distributed in the composites, although some pores existed. The wear resistance and fracture toughness increased with an increasing CNT fraction, but the composite specimen containing 3.0 vol pct of CNTs hardly showed an increase over the specimen containing 2.25 vol pct of CNTs. Observations of worn surfaces revealed that the wear mechanism involved both the abrasive and delamination wear modes in the specimens containing 0 to ~0.75 vol pct of CNTs, whereas the surface was worn largely in an abrasive wear mode in the specimens containing 1.5 to ~3.0 vol pct of CNTs. This was because CNTs helped to change the delamination wear mode to the abrasive wear mode by preventing crack initiation and propagation at alumina grains. The fracture toughness increase provided beneficial effects in the resistance to crack initiation and propagation, the reduction in delamination wear on the worn surface, and the consequent improvement in wear resistance. Because the effect of the porosity increase due to the CNT addition unfavorably affected the improvement of wear resistance and fracture toughness in the specimen containing 3.0 vol pct of CNTs, the appropriate level of CNT fraction was 1.5 to ~2.25 vol pct.     

Hot Extrusion of A356 Aluminum Metal Matrix Composite with Carbon Nanotube/Al2O3 Hybrid Reinforcement

Over the years, the attention of material scientists and engineers has shifted from conventional composite materials to nanocomposite materials for the development of light weight and high-performance devices. Since the discovery of carbon nanotubes (CNTs), many researchers have tried to fabricate metal matrix composites (MMCs) with CNT reinforcements. However, CNTs exhibit low dispersibility in metal melts owing to their poor wettability and large surface-to-volume ratio. The use of an array of short fibers or hybrid reinforcements in a preform could overcome this problem and enhance the dispersion of CNTs in the matrix. In this study, multi-walled CNT/Al₂O₃ preform-based aluminum hybrid composites were fabricated using the infiltration method. Then, the composites were extruded to evaluate changes in its mechanical properties. In addition, the dispersion of reinforcements was investigated using a hardness test. The required extrusion pressure of hybrid MMCs increased as the Al₂O₃/CNT fraction increased. The deformation resistance of hybrid material was over two times that of the original A356 aluminum alloy material due to strengthening by the Al₂O₃/CNTs reinforcements. In addition, an unusual trend was detected; primary transition was induced by the hybrid reinforcements, as can be observed in the pressure–displacement curve. Increasing temperature of the material can help increase formability. In particular, temperatures under 623 K (350 °C) and over-incorporating reinforcements (Al₂O₃ 20 pct, CNTs 3 pct) are not recommended owing to a significant increase in the brittleness of the hybrid material.     

机械球磨与放电等离子体烧结制备碳纳米管/铜复合材料

采用机械球磨和放电等离子体烧结(SPS)工艺制备了碳纳米管(CNTs)/铜复合材料.利用SEM和TEM对材料组织和形貌进行了表征,研究了球磨时间、CNTs含量、SPS烧结压力对复合材料组织和性能的影响.结果表明:质量分数为1％的CNTs可在铜基体中获得良好分散;CNTs与铜基体界面结合良好,有利于应力在基体与CNTs之...     

碳纳米管增强铝基复合材料的力学和物理性能

采用磁力搅拌与放电等离子烧结技术制备了碳纳米管(CNT)增强铝基复合材料.对试样进行了扫描电镜和透射电镜表征,测试了试样的力学性能、摩擦性能、电学性能和热学性能.当碳纳米管在试样中的质量分数为1%时,可在铝基体中均匀分布且CNT/Al界面结合良好,此时试样的抗拉强度和硬度较纯A1分别提高了29.4%和15.8%.在获得最佳力学性能强化和最佳减磨效果的同时.试样电导率较纯Al仅降低8.0%.碳纳米管可提高基体的热导率.但强化效果不明显.      

Preparation and CO conversion activity of ceria nanotubes by carbon nanotubes templating method

Ceria nanotubes with high CO conversion activity by means of carbon nanotubes as removable templates in the simple liquid phase process were fabricated under moderate conditions. The pristine CNTs were first pretreated by refluxing in a 30% nitric acid solution at 140 ℃ for 24 h, then dispersed in an ethanolic Ce（NO3）3.6H2O solution with ultrasonic radiation at room temperature for 1 h. Under vigorous stirring, NaOH solution was added drop by drop into the above ethanolic solution until the pH value was 10. The product was collected and repeatedly washed with ethanol and on drying at 60 ℃, the CeO2/CNT composites were obtained. Then, the as-prepared composites were heated at 450 ℃ in an air atmosphere for 30 min to remove CNTs. The ceria nanotubes were characterized by X-Ray Diffraction （XRD）, Transmission Electron Microscopy （TEM）, and X-Ray Photoelectron Spectrum （XPS）. The results showed that the ceria nanotubes were polycrystalline face-centered cubic phase and were composed of lots of dense cefia nanoparficles. The diameter of cefia nanotubes was about 40-50 nm. Catalytic activity of the product for CO oxidation was carded out at the region of 30-300 ℃ in a U-shaped quartz reactor with feeding about 0.15 g of the catalyst, which was loaded on Al2O3 carder. The inlet gas composition was 1.0% CO and 28% O2 with N2 as balance, and the rate of flow was kept at 40 ml/min. The catalytic products were analyzed by gas chromatography. The as-repared CeO2 nanotubes showed higher CO oxidation activity, which indicated that the morphology of ceria products affected the catalytic performance. The ceria nanotubes supported on Al2O3 demonstrated that conversion temperature for CO oxidation to CO2 was lower than that for bulk catalysts.     

Consolidation of Carbon Nanotube Reinforced Aluminum Matrix Composites by High-Pressure Torsion

Al-3 vol pct carbon nanotube (CNT) composites are fabricated by consolidation through high-pressure torsion (HPT) at room temperature. The densification behavior, microstructural evolution, and mechanical properties of Al/CNT composites are studied. The results show that density and microstructural homogeneity increase with increasing number of revolutions under a high pressure of 6 GPa. Substantial grain refinement is achieved after 10 turns of HPT with an average grain thickness of ~38 nm perpendicular to the compression axis of HPT. The Al/CNT composite shows a considerable increase in hardness and strength compared to the Al matrix. The strengthening mechanisms of the Al/CNT composite are found to be (i) grain refinement of Al matrix and (ii) Orowan looping. Raman spectroscopy and high-resolution transmission electron microscopy reveal that the structure of most of CNTs is changed during processing through mechanical milling and HPT.     

镀钨碳纳米管增强镁基复合材料的摩擦磨损性能研究

以羰基钨为前驱体, 采用金属有机化学气相沉积在碳纳米管表面镀覆了金属钨, 利用磁力搅拌混粉和放电等离子体烧结制备了镀钨碳纳米管增强镁基复合材料((W-CNTs) /Mg), 研究了W-CNTs质量分数对复合材料摩擦磨损性能的影响。结果表明: W-CNTs的加入可对镁基体起到降低摩擦系数、减少磨损量的作用; 当W-CNTs质量分数为0.75%时, 复合材料的摩擦系数和磨损量均最小, 分别较纯镁降低了43.7%和71.4%;增加或降低复合材料中的W-CNTs质量分数, 材料的摩擦系数、磨损量均将增大。(W-CNTs) /Mg复合材料的摩擦磨损性能高于CNTs/Mg复合材料。