固定床吸附废水中Cr（Ⅵ）离子的数学模型

研究了２种煤质活性炭对不同浓度６价铬离子溶液的吸附，应用固定床吸附动力学模型，Ｍａｒｑｕａｄ方法非线性回归固定床吸附流出曲线数据，获得了铬离子在活性炭上的扩散传质系数。结果发现，孔扩散系数ＤＰ强烈地依赖于铬离子入口的浓度，随着入口浓度升高，孔扩散系数变小。     

液固体系固定床吸附器流出曲线预测模型──活性炭吸附水中酚的研究

建立了液固体系的固定床吸附预测模型,并用正交配置法获得了模型方程的数值解,实验测定了苯酚在活性炭上的静态和动态吸附数据,采用Marquadt法优化固定床吸附流出曲线数据,得到了不同浓度条件下的表面扩散系数及其变化规律,并据此预测了其他操作条件下的穿透曲线,预测曲线与实验结果相符甚好．     

煤沥青基球形活性炭苯酚吸附动态研究

本文采用煤沥青制备了吸附性能良好的球形活性炭，并用动态法研究了苯酚在其上的吸附，获得了苯酚—活性炭体系的吸附等温线及传质扩散系数，这些参数被用于理论预测固定床吸附器的苯酚吸附流出曲线，结果表明实验结果能与理论预测相符甚好，动态法研究吸附能获取对吸附工程设计有益的设计参数。     

低浓度三氯乙烯活性炭吸附净化及数值模拟

对低浓度三氯乙烯在活性炭固定床中的吸附净化作了系统研究。测定了三氯乙烯-空气-活性炭系统吸附等温线及在40×120mm活性炭固定床中穿透曲线;建立了三氯乙烯活性炭固定床吸附数学模型并用此预测了穿透曲线,实验与计算结果对比表明模型预测与实验结果吻合良好。     

一种改进的LDF模型及其在活性炭吸附中的应用

以固相表面扩散模型为基础,研究了活性炭在不同吸附质浓度下单颗粒的吸附速率与吸附量之间的关系,以及颗粒内浓度分布随时间的变化过程。结合文献对LDF模型的假设,认为吸附初期对吸附剂颗粒内浓度分布做抛物线假设误差较大,吸附初期颗粒表面浓度分布梯度偏低,使得吸附速率降低,并提出了改进后的LDF模型,最后结合固相表面扩散模型和活性炭颗粒吸附SO₂固定床穿透实验曲线进行了验证。结果表明,采用改进后的LDF模型作为推动力方程的穿透曲线模型能够更加准确地描述实验过程。本文的研究结果能够为活性炭吸附过程提供理论依据和模型参考。     

活性炭吸附处理含酚废水的研究进展

含酚废水对环境和生物有较大危害,是一种常见的化工废水。活性炭作为良好的吸附剂被广泛用于污水处理,也常被用于吸附处理含酚废水。最新的研究集中于开发利用各种含碳原材料,并探究活性炭制备和改性方法,以改善活性炭对酚类的吸附性能。部分机理研究则关注活性炭的孔隙结构和表面官能团及其对吸附酚类性能的影响。本文从活性炭的制备和改性出发,归纳整理活性炭吸附酚类的特性和机理,分析吸附过程的主要影响因素,并对研究发展方向进行推论和展望。分析表明含碳量高的原材料适合制备活性炭,尤其是含碳废弃物。活性炭的苯酚吸附性能受比表面积和表面官能团的共同影响,这对于活性炭的制备和改性有指导意义。活性炭吸附苯酚的具体应用中,需要控制粒度、pH、温度、吸附时间和竞争吸附等影响因素。     

生物质基活性炭处理含酚废水研究进展

介绍了活性炭吸附酚类物质的动力学和热力学机理,简述了近几年活性炭处理含酚废水的相关实践,并对生物质基活性炭的制备、表面改性,吸附饱和活性炭的再生技术、与其它水处理技术联合使用的情况等进行了归纳。认为对于活性炭处理含酚废水的技术应用,需要在高效生物质基活性炭的制备工艺基础上,探索最佳的吸附处理工艺技术,并与其它废水处理技术相结合,开展进一步的研究。     

对二甲苯在活性炭固定床上的吸附动力学

研究了对二甲苯在活性炭固定床上的吸附动力学。考察了初始浓度、气体流量、床层长度等因素对吸附透过曲线的影响。同时,采用Yoon—Nelson模型对吸附透过曲线进行线性回归分析。实验结果表明,随着初始浓度的增大,透过时间缩短,吸附量增大：气体流最对透过曲线的形状影响不大：床层长度基本不影响透过曲线;Yoon-Nelson模型可以较好的模拟固定床吸附过程。     

液相流体在固定填充床中的轴向扩散

用传递函数法求出不同流速、不同装填条件下的固定床流体轴向扩散系数D_(ax),并采用Lax-Wendroff差分格式对固定床对流扩散偏微分方程进行了数值解,比较了轴向扩散系数对固定床流出曲线的影响。     

酸改性活性炭对甲苯、甲醇的吸附性能

分别用1 mol·L^-1硝酸、1 mol·L^-1盐酸、1 mol·L^-1硫酸对商业活性炭进行浸渍改性。采用比表面积及孔径分析仪、Boehm滴定、傅里叶转换红外光谱(FTIR)对活性炭的物化性质进行表征。以甲苯、甲醇为吸附质,在283 K下进行了固定床吸附实验。研究表明:酸改性能去除表面碱性基团,显著增加表面酸性含氧官能团的含量;酸改性活性炭的吸附量与其比表面积、总孔容、微孔孔容、表面总酸性官能团呈现出良好的线性关系;Langmuir方程比Freundlich方程更加适合描述甲苯、甲醇在活性炭上的吸附;甲醇在活性炭上为物理吸附,甲苯在活性炭上以物理吸附为主,与表面官能团之间的化学键作用能增强甲苯吸附量;甲苯、甲醇在活性炭上的微孔有效扩散系数的大小顺序为:AC-N>AC-1>AC-S>AC-C;并且甲醇的微孔有效扩散系数大于甲苯。     

大孔吸附树脂HZ816对红霉素的固定床吸附过程研究

在上柱质量浓度为2.31—6.56 mg/mL、流量为14.33—42.80 mL/h的范围内研究了固定床吸附柱中大孔吸附树脂HZ816对红霉素的动态吸附过程,考察了原料液质量浓度和进口流量等操作参数对穿透曲线的影响。并采用基于液膜及孔内扩散模型的动力学模型,同时考虑吸附树脂颗粒内外扩散阻力及轴向扩散的影响,研究了固定床上红霉素在大孔吸附树脂中的吸附动力学,并从穿透曲线回归得到液膜传质系数孔内扩散系数。结果表明,在实验范围内,该模型能较好地描述红霉素在HZ816树脂上的吸附过程,由模型拟合得到的液膜传质系数随着原料液质量浓度减小而增大,随着流量升高而增大;孔内扩散系数随着原料液质量浓度增大而减小,随着流量升高而减小。为采用大孔吸附树脂HZ816吸附技术分离纯化红霉素工艺提供了实验和理论基础。     

Modeling hydrogen fluoride adsorption by sodium fluoride

In the current study, hydrogen fluoride (HF) adsorption onto the sodium fluoride pellets is modeled. For this purpose a two-dimensional, non-isothermal model was developed and the governing equations were solved numerically. The contributions of diffusion transport in axial and radial directions also were considered in mathematical formulations. The model results of effluent concentration and breakthrough curves of HF were compared with the experimental data obtained in a lab-scale adsorption unit, reported in our previous work [1]. The results indicate while the feed gas velocity decreases, the HF adsorption capacity on NaF is significantly enhanced and there is a delay in breakthrough time. The adsorption capacity of HF on NaF decreases slightly when inlet HF concentration increases. Moreover, the model results were compared with the obtained results from a one-dimension model. This comparison indicates that one-dimensional model can well predict the HF dynamic adsorption behavior for lab-scale fixed beds. Comparing the experimental breakthrough curves of HF adsorption on NaF pellets with the model results shows the ability and accuracy of the model with maximum 7.82% errors.     

活性炭吸附提取氰化亚金离子的数学模拟

以含金工业废水的处理装置为研究对象及镍离子代替氰化亚金离子,对Φ0.2 m×0.5 m吸附柱中活性炭吸附氰化亚金离子进行数学模拟,得到不同条件下氰化亚金离子的吸附柱穿透曲线和吸附负荷分布曲线. 结果表明,当氰化亚金离子的进料流量为0.001 m3/s,进料浓度为 7.614′10-5 kmol/m3,传质系数为0.001 s-1时,吸附床层开始穿透时间为47.61 h,完全被穿透时间为124.14 h;增大进料流量和进料浓度可提高床层被穿透的速度,而当传质系数≥0.001 s-1时,氰化亚金离子吸附穿透曲线不再随传质系数增大而变化.     

Simulation of Levulinic Acid Adsorption in Packed Beds using Parallel Pore/Surface Diffusion Model

The adsorption of levulinic acid in fixed beds of basic polymeric adsorbents at 22 °C was studied under various operating conditions. A general rate model which considers pore diffusion and parallel pore/surface diffusion was solved numerically by orthogonal collocation on finite elements to describe the experimental breakthrough data. The adsorption isotherms, and the pore and surface diffusion coefficients were determined independently in batch adsorption studies. The external film resistance and the axial dispersion coefficient were estimated by the Wilson‐Geankoplis equation and the Chung‐Wen equation, respectively. Simulation elucidated that the model which considers parallel diffusion successfully describes the breakthrough behavior and gave a much better prediction than the model which considers pore diffusion. The results obtained in this work are applicable to design and optimizes the separation process.     

Analysis of some adsorption experiments with activated carbon

A simple method is proposed whereby the film transfer coefficient and coefficient of diffusion in the particles may be determined from finite bath adsorption experiments. The method also makes it possible to separate pore and surface diffusion. Under certain conditions it is also possible to determine the influence of particle phase concentration on the surface diffusivity. The method is based on models describing the instationary diffusion in the solids. Data from six different adsorption systems were analysed using this method. The adsorbed components were: phenol, paranitrophenol, parachlorophenol, bensoic acid, phenylacetic acid and 2-4-dichlorophenoxyacetic acid. In all systems surface diffusion was the determining transport mechanism in the particles. In the system phenol and phenylacetic acid the surface diffusion coefficient increased by about a factor 3 with an increase in surface concentration of about 40%. For parachlorophenol the increase was somewhat less. For the other systems there was no significant increase. The increase in diffusivity is explained by a decrease in bonding forces with increasing concentration.     

Kinetic analysis of phenol adsorption from aqueous systems

The kinetic adsorption of mixtures of phenolic compounds onto a polymeric adsorbent from aqueous solutions was studied. Experimental data for single‐component solutions were obtained and fitted to a parallel diffusion model. Effective diffusion coefficients were related to liquid‐phase diffusion and surface diffusion. The effect of solute concentration and salinity on these parameters was also analysed. Van Laar's equation is proposed to evaluate the influence of concentration on diffusion. The adsorption kinetics for phenol and pcresol mixtures at different initial concentration ratios were determined and correctly adjusted to the mentioned kinetic model. Results confirm that adsorption from multicomponent aqueous solutions is a surface diffusion‐controlled process.     

Solution to the homogeneous surface diffusion model for batch adsorption systems using orthogonal collocation

A solution to the homogeneous surface diffusion model has been developed and incorporated into a batch adsorption model based on external boundary layer mass transport and homogeneous diffusion. The model has been extensively tested using three experimental adsorption systems, namely, phenol on carbon, basic yellow dye on carbon and basic blue dye on silica. The effect of initial solute concentration and adsorbent mass has been studied in 23 batch experiments, which have been modelled using the collocation solution method to solve the homogeneous surface diffusion equation. The theoretical concentration decay curves show a high degree of correlation with experimental data.     

Adsorption of phenanthrene on activated carbons: Breakthrough curve modeling

The modeling of breakthrough curves obtained in the adsorption of phenanthrene as model compound on different activated carbons is described. All the runs were performed in a fixed bed reactor at atmospheric pressure, with a process temperature of 150 °C and low contaminant concentrations. Therefore, experimental conditions were similar to the observed in the flue gases of energy generation systems. This work is mainly focused on the study of how adsorbent characteristics (surface area and micropore size distribution) influence the kinetics of the adsorption process. First, equilibrium values are found from the breakthrough curves and they are satisfactory fitted to the Freundlich isotherm. Using the obtained equilibrium values together with the linear driving force model as kinetic expression, the breakthrough curve modeling is achieved. It was found that this model fits all the breakthrough curves and it is a useful tool for modeling purposes. Values for the phenanthrene surface and effective diffusion coefficients are calculated and reported, and a relationship with the microporosity is found. As it was expected, it is observed that the phenanthrene molecule finds kinetic restrictions for the diffusion in those carbons with narrow microporosity, especially in those with a mean pore diameter close to the molecular size.     

Dynamical adsorption in fixed bed

The behavior of an adsorbent fixed-bed had been investigated for irreversible equilibrium when the adsorption rate is limited by internal diffusion. Breakthrough curves equations has been established for spherical or cubic sorbent particles considering axial dispersion. It has been found out a linear law between the extrapolated breakthrough time and the inverse of adsorbate flowrate. That allows the evaluation of internal diffusion and axial dispersion coefficients.The breakthrough curves of propylene on 13X molecular sieves are interpreted accurately when it is admitted that the adsorption rate is limited by the action of combined internal and external difrusions and when the axial diffusion is taken into account.When the axial diffusion is neglected, the breakthrough curves can be also computed but the coefficients of mass transfer chosen for a good fitting do not agree with those predicted by classical formula.