Mass transfer mechanisms in fixed-bed adsorption of erythromycin

The equilibrium and kinetic characteristics of the adsorption of erythromycin to Sepabeads SP825 were determined. The equilibrium data in a batch system was well described by a Langmuir isotherm. The separation performance was investigated in a fixed-bed system with respect to the adsorption superficial velocity, ionic strength and pH. A mathematical model was used to simulate the mass transfer mechanism, taking film mass transfer, pore diffusion and axial dispersion into account. The model predictions were consistent with the experimental data and were consequently used to determine the mass transfer coefficients.     

Dynamic modeling of fixed-bed adsorption of flue gas using a variable mass transfer model

This study introduces a dynamic mass transfer model for the fixed-bed adsorption of a flue gas. The derivation of the variable mass transfer coefficient is based on pore diffusion theory and it is a function of effective porosity, temperature, and pressure as well as the adsorbate composition. Adsorption experiments were done at four different pressures (1.8, 5, 10 and 20 bars) and three different temperatures (30, 50 and 70 °C) with zeolite 13X as the adsorbent. To explain the equilibrium adsorption capacity, the Langmuir-Freundlich isotherm model was adopted, and the parameters of the isotherm equation were fitted to the experimental data for a wide range of pressures and temperatures. Then, dynamic simulations were performed using the system equations for material and energy balance with the equilibrium adsorption isotherm data. The optimal mass transfer and heat transfer coefficients were determined after iterative calculations. As a result, the dynamic variable mass transfer model can estimate the adsorption rate for a wide range of concentrations and precisely simulate the fixed-bed adsorption process of a flue gas mixture of carbon dioxide and nitrogen.     

MODELING ERYTHROMYCIN ADSORPTION TO THE MACROPOROUS RESIN SEPABEAD SP825

We examined the adsorption of aqueous erythromycin (EM) to the macroporous resin Sepabead SP825 in a series of batch experiments. The equilibrium data were well described by a Langmuir isotherm. The free energy, enthalpy, and entropy of adsorption were calculated, and a film and pore diffusion model was used to simulate the mass transfer mechanism, taking into account diffusion across the liquid film surrounding individual particles and diffusion within the resin particle. The model predictions were consistent with the experimental data and consequently were used to determine the mass transfer coefficients.     

基于改进型吸附等温线模型的空气预纯化TSA双层床模拟

为了掌握空气中CO2和水蒸气在空分装置双层床变温吸附(TSA)纯化器中的动态吸附特性,通过LDF传质假设及非绝热假设,建立了一维二元稀组分系统的双层床TSA过程数学模型。一种改进型的多组分等温线模型用于描述水蒸气的Ⅱ型吸附等温线以及水蒸气和CO2混合物的吸附平衡关系。通过对比模拟结果与TSA纯化器的现场监控数据发现,基于改进型等温线模型的模拟结果与现场数据吻合良好。最后对多种工况下的TSA纯化器中的温度、浓度及吸附量床层分布和穿透曲线进行了数值模拟和分析。     

活性炭纤维填充床内多组分竞争吸附

建立了活性炭纤维填充床内多组分竞争吸附传质动力学模型 ,采用正交配置方法求解数学模型以预测突破曲线 ,从理论上探讨了竞争吸附平衡及吸附质在填充床内的轴向弥散、纤维内扩散和纤维外对流传质等因素对强、弱吸附组分突破曲线的影响。在间歇和填充床吸附器内进行了脱除水溶液中酚类化合物的实验 ,测定了活性炭纤维吸附水溶液中苯酚和氯代苯酚的吸附等温线 (间歇吸附 )以及苯酚和氯代苯酚在活性炭纤维填充床内竞争吸附时的突破曲线 ,并与模型计算值进行了比较。结果表明 ,吸附质在活性炭纤维内扩散和纤维外对流传质阻力不是填充床内吸附过程的控制步骤 ,而轴向弥散影响显著 ,不可忽略     

Theoretical and experimental SO2 adsorption onto pistachio-nut-shell activated carbon for a fixed-bed column

The adsorption and desorption behaviours of SO₂ onto activated carbons, which were prepared from pistachio-nut shells, were studied theoretically and experimentally in a fixed-bed column. A mathematical model considering non-equilibrium, non-isothermal and non-adiabatic effects for a single gas adsorbate on a fixed-bed system was derived and the model was solved by a finite-difference method. A linear driving force (LDF) approximation is used for heat and mass transfer rates. The temperature-dependent Langmuir equilibrium isotherm is used to represent gas–solid equilibrium isotherm. The theoretical study was conducted to compare the present model with the isothermal and adiabatic model. The effects of inlet concentration, flow rate and temperature were studied experimentally. These experimental data showed that the breakthrough time decreased with increasing feed concentration, increasing flow rate and increasing temperature and the trends were correctly predicted by the model calculations.     

固定床动力学模型在离子交换过程中的应用

为了掌握所选的Thomas模型,Yoon-Nelson模型和Adams-Bohart模型在固定床米格列醇离子交换过程中的应用情况,实验借助对不同质量浓度的米格列醇溶液在定量树脂和固定流速下研究其在固定床中离子交换过程,并通过对透过曲线实验数据分析来验证相关固定床动力学模型在此过程中的有效性。结果表明:固定床上样液质量浓度增大,达到平衡饱和点的时间将缩短,传质区长度增大,吸附率变小,上样液质量浓度在8 mg/mL时吸附量达到最大;用动力学模型拟合透过曲线的过程参数,结果表明Thomas模型和Yoon-Nelson模型具有较好的相关系数,Thomas模型的速率常数和最大吸附量值随着上样液质量浓度的降低而增大,Yoon-Nelson模型的速率常数随着上样液质量浓度的降低而减小,且在Yoon-Nelson模型中计算得到的透过曲线中出口质量浓度与上样质量浓度比值为1/2时所对应的计算值和实验值相差很小,Thomas模型和Yoon-Nelson模型可用于该过程的离子交换性研究。     

红霉素在大孔树脂上的吸附动力学研究

采用液膜及孔内扩散模型,模拟不同温度和不同红霉素(EM)初始浓度条件下,大孔吸附树脂HZ816及XAD16吸附红霉素的动态吸附曲线,并获得液膜传质及孔内扩散系数;考察了温度及溶质浓度对红霉素在两种树脂中吸附动力学的影响.结果表明,在实验范围内,红霉素在HZ816和XAD16两种树脂上的吸附平衡数据满足Langmuir吸附等温线方程,液膜及孔内扩散模型能较好地描述红霉素在两种树脂上的吸附动力学,同时,模型拟合得到的液膜传质系数随着温度的升高而增大,随着初始浓度的增大而增大,孔内扩散系数随着温度的升高而增大,随着初始浓度的增大而减小.     

AB-8大孔树脂对葡萄籽原花青素的吸附过程

研究葡萄籽原花青素粗提液在AB-8大孔树脂上的吸附过程,建立了AB-8大孔树脂吸附原花青素的相平衡方程和动态吸附模型,计算了不同流速、不同进料浓度下的总传质系数、传质区长度及穿透时间。实验结果表明,原花青素静态吸附符合Langmuir吸附等温方程式;AB-8树脂对原花青素的动态吸附属于外扩散控制过程;穿透时间计算值与实验值一致。建立的数学模型可用于指导实际生产操作,为吸附柱的设计提供参考。     

Simulation and validation of ethanol removal from water in an adsorption packed bed: Isotherm and mass transfer parameter determination in batch studies

Preferential adsorption of ethanol from ethanol/water mixtures in batch equilibrium and kinetic experiments were carried out on a commercially available activated carbon adsorbent Filtrasorb 600 (F‐600). A model based on finite difference method was developed and employed to determine the mass transfer parameters and equilibrium behaviour for the adsorption of ethanol from simple batch systems. The estimates of the adsorption isotherm along with the mass transfer parameters were used to simulate the transient performance that could be expected in a packed bed under various operating conditions (feed flow rate, feed concentration, and particle size). The applicability of the simulation results were found to be a good match with experimental packed bed experiments over the entire range of operating conditions tested.     

固定床吸附分离C_8芳烃的数学模型

以自制和进口Y型合成沸石在室温下液相吸附分离对二甲苯-乙苯二元体系,研究固定床吸附分离C_8芳烃的数学模型.数模中的传质速率方程用总传质系数表征其传质特点,结合相平衡和物料衡算方程,进行数值积分,得到的理论透过曲线与实验曲线相近.为了进一步探索吸附过程动力学和传质机理,对液相控制、固相控制和固液相联合控制三种数学模型进行了初步探索和比较,发现固相控制模型更适合本研究体系.     

EPA和DHA在超临界流体色谱柱中的传质动力学

用超临界流体色谱 (SFC)法研究了EPA和DHA在C18上的吸附和传质性能 .建立了色谱动力学模型并获得了模型参数 ,较好地拟合了实验流出曲线 .结果表明吸附平衡、轴向弥散、流体相传质和颗粒内有效扩散都是影响SFC分离EPA和DHA的重要因素     

Development of design charts for fixed-bed adsorption

A mathematical model of the dynamic behaviour of non-isothermal fixed-bed adsorbers has been developed which takes into account the various mass and heat transfer resistances. Comparison of experimental and simulated results confirms that the model can predict the adsorption and desorption breakthrough curves of an adiabatically operated column, using only equilibrium data and tortuosity factors obtained from single pellet experiments. A simplified model with a reduced number of parameters was derived by investigation of the dimensionless transfer parameters under industrial conditions. It becomes evident that the main transfer mechanisms are convective heat and mass transfer in the bulk flow and diffusion within the pores of the particle. Dimensionless effluent concentration is expresses in terms of dimensionless time, a transport parameter, a non-isothermal parameter, the adsorption equilibrium and the inlet and initial concentrations and temperatures in the simplified model. For a chosen system of adsorbate and adsorbent, design charts can be developed by computer simulation, to determine graphically the breakthrough time as a function of significant process parameters, i.e. the dimensionless transfer parameter and the feed concentration.     

CR型吸附剂对蔗糖和还原糖的吸附特性

本文提出液相色谱技术测定吸附相平衡常数和传质系数参数的估值模型，测定蔗糖还原糖在碱土金属型的ＣＲ型吸附剂上的吸附相平衡常数和总传质系数。结果表明：吸附相平衡常数随温度的升高而下降，吸附剂的选择性也随之下降；液固相间的总传质系数随温度的升高而增大，并随流速的增大而增大。在三种ＣＲ型吸附剂中，ＣＲ－２型吸附剂有较好的传质动力学性能和对还原糖吸附有较大的选择性。     

Isotherm parameters and intraparticle mass transfer kinetics on molecularly imprinted polymers in acetonitrile/buffer mobile phases

The equilibrium isotherm and the intraparticle mass transfer kinetics of the enantiomers of the template were investigated on an Fmoc-L-tryptophan (Fmoc-L-Trp) imprinted polymer at different pHs and water concentrations in acetonitrile/aqueous buffer mobile phases. The equilibrium isotherm data were measured using frontal analysis at . The adsorption energy distribution was found to be trimodal, with narrow modes. Consistent with this distribution, the adsorption data were modeled using a tri-Langmuir isotherm equation and the best estimates of the isotherm parameters were determined. The intraparticle mass transfer parameters were derived by comparing the profiles of experimental overloaded bands and the profiles calculated using the isotherm model and the lumped pore diffusion (POR) model of chromatography. These results showed that different adsorption and mass transfer mechanisms exist in mobile phases made of acetonitrile/aqueous buffer and of acetonitrile/acetic acid solutions.     

Study on mass transfer of ethyl acetate in polymer adsorbent by experimental and theoretical breakthrough curves

A new polymeric adsorbent with highly hypercrosslinked structure was developed for the removal of VOCs from polluted air. The purpose of this work is to obtain the intraparticle mass transfer coefficient of the adsorbent particles. Adsorption experiments for obtaining breakthrough curves were carried out with a fixed bed system. A dynamic mathematical model for the fixed bed adsorption system was developed. By model fitting, the overall mass transfer coefficient was determined when the deviation error was minimum. Then, the intraparticle mass transfer coefficient of the adsorbent was determined when the external mass transfer resistance was eliminated at higher velocities. Furthermore, a linear relationship of the intraparticle mass transfer coefficient and equilibrium coefficient at lower inlet gas concentrations range was correlated. Moreover, an equation for predicting external mass transfer coefficient at low Reynolds number range at room temperature was obtained.     

The Adsorption of Pollutants by Peat,Lignite and Activated Chars

The ability of peat, lignite and activated chars made from peat and lignite to adsorb dyes and metals from wastewater and NO₂ from air was investigated. Equilibrium isotherms were determined to assess the maximum adsorption capacity of the adsorbents for the pollutants. Kinetic studies for the adsorption of dyes and metal ions onto the adsorbents were undertaken in agitated batch adsorbers. Mass transport models were tested to predict the concentration decay curves in batch adsorbers. The models tested were single resistance models based on the assumption of a single external mass transfer coefficient and two resistance models which included an internal diffusion coefficient and an external mass transfer coefficient. The surface phenomena which influence the extent and the rate of uptake have been studied. The equilibrium capacity data conform to Langmuir plots. A previously proposed model was used to evaluate the external single resistance mass transfer model and was successfully applied to predict the adsorption of metal ions in single component systems under batch conditions. It has been shown that the assumption of negligible intraparticle diffusion is valid and that external film diffusion is the rate limiting step in describing the adsorption processes at high sorbent loadings. The same type of result is not observed for the adsorption of coloured organic matter onto peat where the sorption processes cannot be successfully modelled by use of a single resistance model and a two resistance model incorporating internal diffusion is required. The surface phenomena which influence the extent and the rate of uptake of NO₂ have been studied. The type of chars produced and the activation processes affect the adsorption. As activation increases, micropore volume and surface area increase and the maximum capacity of the adsorbent increases. Surface area alone is not the only parameter which affects equilibrium uptake. © 1997 SCI.     

固定床吸附烷烃中芳烃的模拟

本文在实验研究烷烃中少量芳烃的固定床吸附动态过程的基础上,进行模型化计算,分别用线性推动力和孔扩散两种固定床吸附模型,拟合得出总传质系数,液膜传质系数和孔扩散系数,两种模型的拟合计算结果表明：在本文的实验条件范围内,传质推动力可用线性推动力表示。总传质阻力由液膜传质阻力和颗粒相传质阻力的共同作用而形成,它随着温度,浓度和流量的降低而增加,孔扩散系数与流量无关。     

余热制冷吸附床的一个新传热传质模型

在既考虑吸附剂颗粒内部的传质阻力,又考虑吸附剂颗粒之间的外部传质阻力的前提下,建立了余热吸附制冷系统中吸附床的三维非平衡传热传质数学模型,它包括加热/冷却流体传热模型、换热管传热模型、肋片传热模型、吸附剂颗粒床传热传质模型4部分;通过对模型的数值求解,获得了吸附床内部的温度演变曲线和性能指标,与实验结果基本吻合。