纸质活性炭纤维的制备及性能表征

通过KOH活化纸巾制备活性炭纤维, 比表面积高达1388 m²/g. 用制得的活性炭纤维作为吸附剂进行亚甲基蓝吸附实验研究,用Langmuir和Freundlich吸附模型分析实验数据,并研究pH值对活性炭纤维吸附亚甲基蓝影响. 活性炭纤维吸附速率更适于Pseudo-second-order动力学模型,相关系数高达0.998. 整个浓度变化区间Langmuir吸附等温线比Freundlich吸附等温线更适合实验数据. 所制备活性炭纤维对亚甲基蓝最大平衡吸附量为520 mg/g,实验发现,pH值越高活性炭纤维对亚甲基蓝吸附量越大.     

气体临界温度以上吸附平衡的预测研究

采用容积法测定了CH4和N2 在微孔活性炭K0 2上的吸附平衡数据 ,温度为 2 73～ 333K ,压力为 0～12MPa .提出了一个可以从单一气体吸附等温线预测其它条件下吸附平衡的理论模型 .该模型考虑了临界温度以上吸附相密度和饱和吸附量与温度的关系 ,并采用孔径分布来表征吸附剂表面吸附势场的不均一性 ,局部方程使用Langmuir描述 .利用此模型预测了CH4和N2 在K0 2活性炭上的吸附平衡 ,在所研究的温度、压力范围内的整体预测偏差不超过 3% .另外 ,对文献中不同实验条件下气体临界温度以上的吸附平衡进行了研究 ,在较宽的范围内也取得了很好的预测结果     

ICP-OES研究活性炭无纺布对镉的吸附

重金属污染是一个相当严重的环境问题。镉具有很强的生物毒性和不可降解性,对生态环境和人体健康有极大威胁,被列为优先控制污染物。环境中镉的主要污染源是电镀、采矿和化学工业等部门的废水,如何简单高效去除水中的镉,有重要的社会意义和经济意义。目前,水中重金属的去除方法有化学沉淀、膜分离、离子交换、吸附、电解等,其中吸附法因简单高效而广泛应用。活性炭纤维是一种新型活性炭,孔径小且均匀,表面官能团发达,吸附性能好,逐步应用于水处理领域。以电感耦合等离子体光谱为检测手段,佐以比表面积分析,X射线衍射,元素分析和傅里叶变换红外光谱,研究比较了三种活性炭纤维(纤维炭网、活性炭无纺布、活性炭纤维毡)的结构特点及其对水中镉的吸附性能。三种活性炭纤维结构基本类似,具有较发达的孔隙结构。活性炭无纺布极性较强,表面有丰富的羟基、羧基、醛基等含氧官能团,对水中镉的吸附作用最大。因此,选择活性炭无纺布为吸附剂进行后续实验。研究了活性炭无纺布吸附镉的影响因素,如溶液pH,吸附时间等。溶液pH影响吸附剂表面电荷及水中镉的存在状态。水中镉的去除效率随溶液初始pH的增大而增大,在较低pH时,吸附剂与Cd2+间存在静电斥力,同时H+和Cd2+存在竞争吸附,pH>9时,镉的去除是吸附与沉淀协同作用的结果,选择pH为6～7。在吸附的初始阶段,活性炭无纺布对Cd2+的吸附量迅速增加,10 min时,吸附率达到72%。随着吸附位点逐渐被Cd2+所填充,吸附速率逐渐变慢,300 min时,吸附容量基本无变化,吸附趋于平衡。优化了镉的吸附条件后,进行等温吸附实验和动力学实验。结果表明,25 ℃时,吸附时间为300 min,pH 6.0条件下,当镉的平衡浓度在20.00 mg·L-1时,活性炭无纺布对镉的单位质量吸附量和单位比表面积吸附量分别是3.04 mg·g-1和0.035 mg·m-2。用Langmuir方程(R2=0.997, K_L =1.796 L·mg-1)和Freundich方程(R2=0.895, K_F=0.918 L·mg-1, n=2.12)拟合活性炭无纺布对镉的等温吸附数据,Langmuir方程计算的理论吸附量为3.07 mg·g-1,与实验值相当,并且线性系数更高,说明该体系的吸附符合Langmuir方程,主要为单分子层吸附。Langmuir分离因子介于0和1之间,表明活性炭无纺布对镉的吸附容易进行。用准一级动力学方程、准二级动力学方程、颗粒内扩散方程和Elovich方程四种动力学模型拟合吸附过程。在吸附的前5 min,镉在活性炭无纺布上的吸附符合颗粒内扩散方程(R2=0.985),吸附主要受颗粒内扩散控制。在吸附的5～300 min,颗粒内扩散方程拟合较差。整个吸附过程符合准二级动力学方程(R2=0.999,k₂=0.367 g·mg-1·min-1),Elovich方程(R2=0.981,a=0.271 mg·g-1, b=0.083 mg·g-1·(lg min)-1)和准一级动力学方程(R2=0.927,k₁=0.008 8 min-1)次之,颗粒内扩散方程(R2=0.785)最差。活性炭无纺布对镉的吸附过程是一种化学作用为主的吸附过程。对5.00 mg·L-1含镉水样,活性炭无纺布投放量为10 g·L-1时,吸附后水中镉的浓度小于0.10 mg·L-1,符合《污水综合排放标准》(GB 8978-1996)。活性炭无纺布可同时吸附镉,铜,铅,铬等重金属离子,选择性较差。但在电镀、采矿等实际废水中重金属种类复杂,适当提高吸附剂投放量,可同时去除多种重金属。利用活性炭无纺布吸附处理含镉水样,处理效果好、操作简单,可以作为去除水中镉的吸附剂,为含镉废水的处理提供了技术支持和理论基础。     

改性生物质活性焦碳管吸附剂汞吸附性能实验研究

本文以稻壳为原料,经H_3PO_4活化、HBr溶液改性,制得用于吸附管离线采样法测试烟气汞浓度的颗粒活性炭,其BET比表面积达853.017 m~2/g,超过一种商业活性炭。将其制成碳吸附管后,在模拟烟气固定床试验装置上进行碳管法烟气汞浓度测试。结果表明:改性稻壳基颗粒活性炭的汞吸附性能与商业活性炭相当,碳吸附管的第二段汞穿透率RB5%,测量相对误差满足EPA 30B碳管法测量精度要求,本文研制的活化改性稻壳焦颗粒活性炭可作为碳管汞吸附剂用于燃煤锅炉烟气中汞的检测分析。     

用格子Boltzmann模型模拟激波现象

根据微观和宏观之间的质量、动量、能量守恒准则,建立了一个两维的D2Q13格子Boltzmann模型,可从该D2Q13模型出发推导出宏观的流体力学方程,所得动量方程和Navier-Stokes方程相比,在黏性输运项上有明显的改进,用该模型对冲击波在障碍物表面上的折射和反射现象的数值模拟都得到了比较满意的结果,而且数值稳定性也很好.证明了D2Q13模型的适宜性 关键词： Boltzmann模型 分布函数 冲击波 流体力学方程     

低温容器内活性炭吸氢性能的模拟研究

以石墨片微元构建活性炭的结构模型,采用巨正则蒙特卡罗(GCMC)方法从微观研究H2在以活性炭为基的复合吸氢剂中的吸附特性,获得了不同条件下复合吸氢剂对H2的吸附过程.结果表明,氧化物吸氢剂修饰对活性炭材料的表面化学性能影响较大,引入之后使其吸氢量增加了一倍以上;氧化物吸氢剂嫁接在活性炭上的不同位置吸氢效果不同,以双键连...     

D4006大孔树脂对水溶液中克百威吸附的热力学

采用分光光度法研究了D4006型大孔树脂对克百威的吸附行为.结果表明克百威在D4006树脂上的吸附量随着温度的升高而减少,吸附过程为放热的物理吸附过程.Freundlich等温方程能很好地描述两种树脂对克百威的吸附.     

一个完全守恒的格子Boltzmann模型

利用六角形格子离散的方法,使得每个六角形Cell里含有 3种不同运动速度的粒子微团,宏观物理量用这些粒子微团的矩来定义.根据微观和宏观之间的质量、动量、能量守恒准则,建立了一个二维的D2Q19格子Boltzmann模型,从该D2Q19模型出发可推导出宏观的流体力学方程组.用该模型对冲击波在障碍物组表面上的折射现象进行数值模拟,并将计算结果与实验进行了比较.     

活性炭在高真空多层绝热中液氮温度下的吸气性能

通过实验获得了活性炭在液氮温度下对N2和H2两种气体的吸附等温线。结果表明:活性炭对N2的吸附效果非常好,对H2的吸附效果较差,相同平衡压力下对N2的吸附量比对H2的吸附量高出2～3个数量级,且在活性炭外包上绝热材料能大大提高其对气体的吸附能力,尤其是对N2的吸附量能提高2～3个数量级,对H2的吸附量也能提高1倍以上。用temkin吸附式对吸附等温线进行拟合,得到了活性炭在10-4～10Pa范围内适用的对N2和H2两种气体的吸附等温方程式。     

银纳米颗粒对四苯基卟啉Q带荧光寿命的延长

文章报道了吸附在银纳米颗粒表面的四苯基卟啉(TPP)的Q带荧光寿命的变化.实验发现将银纳米颗粒的表面等离激元共振吸收峰调至与TPP的Q吸收带共振时,会使TPP的Q带荧光寿命得到延长.这是由于银纳米颗粒对表面的光电场有较大的表面等离激元共振增强效应,而处于激发态的TPP分子有较高的极性,这种增强的光电场会对有较高极性的TPP分子有稳定作用,所以延长了其Q带寿命.这对于以卟啉为光敏剂的光动力治疗有重要的意义.     

Characterization of partially sintered ceramic powder compacts using fluorinated gas NMR imaging.

We use nuclear magnetic resonance (NMR) imaging of C2F6 gas to characterize porosity, mean pore size, and permeability of partially sintered ceramic (Y-TZP Yttria-stabilized tetragonal-zirconia polycrystal) samples. Conventional measurements of these parameters gave porosity values from 0.18 to 0.4, mean pore sizes from 10 nm to 40 nm, and permeability from 4 nm(2) to 25 nm(2). The NMR methods are based on relaxation time measurements (T(1)) and the time dependent diffusion coefficient D(Delta). The relaxation time of C2F6 gas is longer in pores than in bulk gas and it increases as the pore sizes decrease. NMR yielded accurate porosity values after correcting for surface adsorption effects. A model for T(1) dependence on pore size that accounts for collisions between gas molecules and walls as well as surface adsorption effects is proposed. The model fits the experimental data well. Finally, the long time limit of D(Delta)/D(o), where D(o) is the bulk gas diffusion coefficient is useful for measuring tortuosity, while the short time limit was not achieved experimentally and could not be used for calculating surface-area to volume (S/V) ratios.     

Surface heterogeneity effects of activated carbons on the kinetics of paracetamol removal from aqueous solution

The removal of a compound with therapeutic activity (paracetamol) from aqueous solutions using chemically modified activated carbons has been investigated. The chemical nature of the activated carbon material was modified by wet oxidation, so as to study the effect of the carbon surface chemistry and composition on the removal of paracetamol. The surface heterogeneity of the carbon created upon oxidation was found to be a determinant in the adsorption capability of the modified adsorbents, as well as in the rate of paracetamol removal. The experimental kinetic data were fitted to the pseudo-second order and intraparticle diffusion models. The parameters obtained were linked to the textural and chemical features of the activated carbons. After oxidation the wettability of the carbon is enhanced, which favors the transfer of paracetamol molecules to the carbon pores (smaller boundary layer thickness). At the same time the overall adsorption rate and removal efficiency are reduced in the oxidized carbon due to the competitive effect of water molecules.     

Factors influencing activated carbon-polymeric composite membrane structure and performance

Hybrid carbon-polymeric composite membranes were synthesized by an immersion-precipitation method using polysulfone as polymer precusor and activated carbon dissolved in dimethyl formamide as casting solution. Surface analysis by scanning electron microscopy (SEM) allowed studying the morphology of membranes as a function of synthesis conditions (carbon loading and particle size). Membrane porosity distribution and mean pore size were obtained numerically using IFME^® program.Effect of casting conditions over carbon was also investigated by SEM.Hybrid membrane performances were characterized in terms of water and oligomeric flux in a continuous operation mode. Selective rejection of dextranes of high molecular weight was obtained. Results showed that permeability for composite membranes is influenced basically by loading and activated carbon particle size, giving rise to materials with a better performance than non-hybrid ones for this application.     

Cellulose Acetate/Activated Carbon Composite Membrane with Effective Dye Adsorption Performance

Abstract

Cellulose acetate (CA) and activated carbon (AC) were used as base material and additive, respectively, to prepare CA/AC composite membranes. By adjusting the AC content (5%, 10%, 15%, and 20%), the morphology and the adsorption capability of the samples for target dyes were studied. The results showed that the surface flatness and compactness of the barrier layer deteriorated with increasing AC content. In addition, the pore size and structures of the supporting layer became large due to the partial agglomeration of the AC in the CA. The relationship between adsorption time and adsorption capability was investigated. It was found that the 15% AC composite membrane possessed the highest adsorption efficiency for acid blue dye. The adsorption equilibrium was 58.69?mg/g for 60?mg/L acid blue dye at 120?min. For acid yellow and acid dark dye, the adsorption equilibria were 58.23 and 58.34?mg/g, respectively.     

Calculation method for particle mean diameter and particle size distribution function under dependent model algorithm

In total light scattering particle sizing technique, the relationship among Sauter mean diameter D32, mean extinction efficiency Q, and particle size distribution function is studied in order to inverse the mean diameter and particle size distribution simply. We propose a method which utilizes the mean extinction efficiency ratio at only two selected wavelengths to solve D32 and then to inverse the particle size distribution associated with (Q) and D32. Numerical simulation results show that the particle size distribution is inversed accurately with this method, and the number of wavelengths used is reduced to the greatest extent in the measurement range. The calculation method has the advantages of simplicity and rapidness.     

随机四参数法生成多孔介质及渗流模拟

本文基于多孔介质内流动的广泛应用背景,模拟了多孔介质渗流.采用随机四参数生长法生成了多孔介质模型,并对模型中的微小固相进行了过滤处理,将随机四参数生长法生成的多孔介质结合格子玻尔兹曼方法D2Q9模型模拟了压力驱动的多孔介质中的渗流.通过将模拟结果与著名的CK理论公式的计算结果进行比较,发现在孔隙率高时误差较小(cp=0...     

孤立碳颗粒聚团燃烧过程的研究

数值模拟气体流过孤立碳颗粒聚团的燃烧反应过程。计算表明穿过颗粒聚团的气体流量主要与颗粒聚团空隙率有关。当颗粒聚团空隙率小于0．8时,穿过颗粒聚团的气体流量可忽略不计。碳颗粒聚团内温度呈现迎来流面低、背流面高,两侧低中间高; CO和CO2含量呈现迎来流面低、背流面高,两侧低中间高的变化趋势;而O2含量迎来流面高、背流面低,两侧高中间低。颗粒聚团内不同位置的颗粒消耗的碳量不同。颗粒的相互团聚将降低碳的消耗量,同时也抑制碳颗粒燃烧过程NO和N2O的生成。     

Coalbed methane adsorption and desorption characteristics related to coal particle size

Effects of particle size on CH_4 and CO_2adsorption and desorption characteristics of coals are investigated at 308 K and pressures up to 5.0 MPa.The gas adsorption and desorption isotherms of coals with particle sizes ranging from 250 μm to 840 μm are measured via the volumetric method,and the Langmuir model is used to analyse the experimental results.Coal particle size is found to have an obvious effect on the coal pore structure.With the decrease of coal particle size in the process of grinding,the pore accessibility of the coal,including the specific surface area and pore volume,increases.Hence,coal with smaller particle size has higher specific surface area and higher pore volume.The ability of adsorption was highly related to the pore structure of coal,and coal particle size has a significant influence on coal adsorption/desorption characteristics,including adsorption capacity and desorption hysteresis for CH_4 and CO_2,i.e.,coal with a smaller particle size achieves higher adsorption capacity,while the sample with a larger particle size has lower adsorption capacity.Further,coal with larger particle size is also found to have relatively large desorption hysteresis.In addition,dynamic adsorption performances of the samples are carried out at 298 K and at pressures of 0.1 MPa and 0.5 MPa,respectively,and the results indicate that with the increase of particle size,the difference between CO_2 and CH_4adsorption capacities of the samples decreases.     

Surface effect on the size evolution of surface plasmon resonances of Ag and Au nanoparticles dispersed within mesoporous silica

The optical absorption has been investigated for silver and gold nanoparticles dispersed within the pores of monolithic mesoporous silica after annealing at different temperatures. It has been shown that with reduction of the particle size, the surface plasmon resonance position blue-shifts first and then red-shifts for silver/silica samples, but only red-shifts for gold/silica samples. This size evolution of the resonance is completely different from that previously reported for fully embedded particles. Based on the interaction of the particle surface with ambient air and the porosity at the particle/matrix interface, we present a multi-layer core/shell model and assume that the chemical adsorption of gas molecules from the air on the free surface of nanoparticles within the pores is mainly responsible for the observed size evolution of the resonance.