用实验吸附等温线和计算机分子模拟表征中孔分子筛MCM-41

首先比较了表征MCM 4 1的两个势模型对吸附等温线的影响 .发现在一维势模型中 ,低压部分的吸附应与选用的势模型的势阱深度有关 ,而毛细凝聚发生的位置与孔壁在离壁面较远处与流体分子的相互作用的强弱有关 .然后作者使用了一个“混合”的势模型 ,即采用作者提出的势函数表征孔壁中氧原子对MCM 4 1中流体分子的作用 ,而采用Tjatjopoulos等提出的势函数近似地表征MCM 4 1表面硅醇基团以及一些未知因子对流体分子的作用 .虽然这种势模型仍然是一维的 ,但这种势模型将孔壁内氧原子的作用和表面上非均匀性分开考虑 ,具有较明确的物理意义 .通过计算机模拟与实验数据的比较发现 ,这种势模型可以较好地拟合氮气在MCM 4 1中的吸附等温线 .

玻尔兹曼因子等温线对气液相变与临界系数的数学描述

应用气体的玻尔兹曼因子方程和液体的玻尔兹曼因子方程共同描述等温压缩二氧化碳气体的全过程，可以得到与安德鲁斯实验实测等温线完全一致的玻尔兹曼因子等温线．特别是，在低于临界温度时，玻尔兹曼因子等温线可以如实地描述从气体体系到气体与液体共存的非均匀体系，再到液体体系的等温压缩全过程；客观地表述了气、液相变与临界系数的自然变化规律；彻底地解决了“范氏方程给出的曲线不包含气、液共存的信息”等缺陷问题．

A Mathematical Method for Determination of Absolute Adsorption from Experimental Isotherms of Supercritical Gases

A mathematical method was proposed for the determination of absolute adsorption from experimental isotherms. The method is based on the numerical equality of the absolute and the excess adsorption when either the gas phase density or the amount adsorbed is not quite considerable. The initial part of the experimentalisotherms, which represents the absolute adsorption, became linear with some mathematical manipulations. The linear isotherms were reliably formulated. As consequence, either the volume or the density of the supercritical adsorbate could be determined by a non-empirical way. This method was illustrated by the adsorption data of supercritical hydrogen and methane on a superactivated carbon in large ranges of temperature and pressure.

Tungsten removal from molybdate solutions using chelating ion-exchange resin:Equilibrium adsorption isotherm and kinetics

The equilibrium adsorption isotherm and kinetic of the sorption process for W and Mo on macro chelating resin D403 were investigated on single Na2 Mo O4 and Na2WO4 solutions.The sorption isotherm results show that the adsorption process of W obeys the Freundlich model very well whereas the exchange process with Mo approximately follows the Henry model.The kinetic experiments show that the intraparticle diffusion process was the rate-determining step for W sorption on the resin,and the corresponding activation energy is calculated to be 21.976 k J/mol.

Improved analytic methods for coal surface area and pore size distribution determination using 77 K nitrogen adsorption experiment

77 K nitrogen adsorption was the most widely used technique for determining surface area and pore size distribution of coal. Brunauer–Emmett–Teller(BET) and Barrett–Joyner–Halenda(BJH) model are commonly used analytic methods for adsorption/desorption isotherm. A Chinese anthracite coal is tested in this study using an improved experimental method and adsorption isotherm analyzed by three adsorption mechanisms at different relative pressure stages. The result shows that the micropore filling adsorption predominates at the relative pressure stage from 6.8E 7 to 9E 3. Theoretically, BET and BJH model are not appropriate for analyzing coal samples which contain micropores. Two new analytic procedures for coal surface area and pore size distribution calculation are developed in this work. The results show that BET model underestimates surface area, and micropores smaller than 1.751 nm account for 35.5% of the total pore volume and 74.2% of the total surface area. The investigation of surface area and pore size distribution by incorporating the influence of micropore is significant for understanding adsorption mechanism of methane and carbon dioxide in coal.

Dye removal using some surface modified silicate minerals

The objective of this work is to study the efficiency of some surface modified phyllosilicate minerals （bentonite and glauconite） in the removal of dyes from textile waste water. It is found that complete dye removal was achieved by using 10-25g modified glauconite from solutions having a dye concentration of 10-50 mg/L. Adsorption data were modeled using Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherms. Adsorption capacities and optimum adsorption isotherms were predicted by linear regression method. The analysis of experimental isotherms showed that Langmuir isotherm reasonably fit the experimental data in the studied concentration range for the adsorption of dye onto glauconite mineral surface where Freundlich isotherm fit the experimental data for the adsorption of dve onto bentonite mineral surface.

Adsorption of Naphthol Green B on unburned carbon：2-and3-parameter linear and non-linear equilibrium modelling

The study deals with adsorption of Naphthol Green B on two unburned carbons and the parent coal,from which the UCs have been created in a fluidised-bed power station.Particular attention has been paid to the adsorption equilibrium modelling:experimental data has been analysed using 2-parameter(Langmuir,Freundlich) and3-parameter(Redlich-Peterson) isotherms — both linear and non-linear regressions have been used for the estimation of the isotherm parameters.In the case of both UCs,the Langmuir isotherm model provides the worst fit,whereas 2-parameter Freundlich and 3-parameter Redlich-Peterson models are both good,from which 3-parameter Redlich-Peterson isotherm provides slightly better results(despite the penalty used for the higher number of parameters).In the case of both UCs,the linear regression of Freundlich and Redlich-Peterson models provides good results(comparable with non-linear regressions).Unlike both UCs,the best fit of the experimental data from the adsorption on the coal has been achieved by the Langmuir isotherm model.The results based on the Freundlich or Redlich-Peterson model were(in this case) somewhat worse.

Equilibrium and kinetics of adsorption of Ca(Ⅱ) ions onto KCTS and HKCTS

The adsorption of Ca（ II ） ions from aqueous solution by ehitosan a-ketoglutaric acid （KCTS） and hydroxamated chitosan a-ketoglutaric acid （HKCTS） was studied in a batch adsorption system. The Langmuir and Freundlich adsorption models were applied to describing the equilibrium isotherms, and isotherm constants were determined. The kinetics of the adsorption with respect to the initial Ca（II） ions concentration, temperature and pH was investigated. The pseudo-first-order and second-order kinetic models were used to describe the kinetic data and the rate constants were evaluated. The results show that the experimental data fit well to the Langmuir isotherms with a high correlation coefficient （R2）. The pseudo-second-order rate expression provides the best fitting kinetic model. The pseudo second-order kinetic model is indicated with the activation energy of 26.22 kJ/mol and 6.16 kJ/mol for KCTS and HKCTS, respectively. It is suggested that the overall rate of adsorption of Ca（ II ） ions is likely to be controlled by the chemical process.

Simulated moving bed separation of tocopherol homologues:simulation and experiments

Chromatograms of tocopherol homologues were obtained by a column of analytical size (inner diameter (ID) 0.46 cm cm×10 cm) packed with silica gel. Adsorption isotherms and film mass-transfer coefficient were estimated from the chroma-tograms by using a general rate model, which considers axial dispersion, external mass-transfer and intraparticle diffusion. Based on the obtained isotherms and mass-transfer coefficient, the separation process of tocopherol homologues on simulated moving bed (SMB) was simulated using the same model. According to the simulated results, a mixture of α-, γ-, δ-tocopherols and other impurities was separated on an SMB equipment. The SMB equipment was composed of 8 columns of ID 2 cm×10 cm, with 2 columns in each section. The solid phase was silica gel, and the mobile phase was n-hexane/2-propanol (99/1 by volume). γ-and δ-tocopherols of purity greater than 98% were obtained with recovery greater than 98%. The effects of operating conditions (flow rates and switching time) on the performance of SMB were studied by both simulation and experiments. It was found that all the simulation results were quite close to the experimental results. We conclude that process development and optimization of operating conditions of SMB by simulation are feasible.

Carbon dioxide sorption and diffusion in coals:Experimental investigation and modeling

CO2 sorption and diffusion in coal are closely related to the occurrence of coal and gas outburst,geological sequestration of CO2 in coalbeds,and enhancing coalbed methane recovery by injecting CO2.Hence,it is significant to investigate the sorption properties and diffusion models of CO2 in coal.Here we used a newly designed experimental apparatus at Peking University to investigate the sorption and diffusion properties of CO2 in natural coal samples from Dashucun Mine and Wutongzhuang Mine in Handan city,Hebei province,and Jinhuagong Mine in Datong city,Shanxi province,and obtained CO2 sorption isotherms and diffusivity models.The results indicate that,in a certain pressure range,CO2 sorption isotherms for the coal samples are consistent with the Langmuir model,which assumes that monolayer sorption occurs at the interface between coal matrix and CO2 molecules,and the sorption isotherms feature nonstandard hyperbolas in mathematics.At the same pressure and temperature,as the vitrinite content increases,coal adsorbs more CO2 molecules.The relation between the sorption capacity and the coal rank may be described as a "U-type" trend,and medium rank coal has the least sorption capacity.The bulk diffusivity of CO2 in coal is not constant;in the range of CO2 mass fraction greater than 1%,it increases roughly linearly with increasing mass fraction of CO2 adsorbed(or CO2 partial pressure) in coal.CO2 diffusivity in coal is approximately 10-4 to 10-2 mm2/s in magnitudes,and the diffusivity ranges in coal samples are 3×10-4 to 8×10-3 mm2/s from Dashucun Mine,2×10-4 to 4×10-3 mm2/s from Wutongzhuang Mine,and 2×10-4 to 4×10-3 mm2/s from Jinhuagong Mine.The results of the CO2 sorption and diffusion study can be applied to help predict and prevent coal and gas outburst as well as to evaluate the feasibility in geological sequestration of CO2 and to enhance coalbed methane recovery.

Adsorption Models and Structural Characterization for Activated Carbon Fibers

The nitrogen adsorption isotherms at 77.69 K were measured for two samples of activated carbon fibers and their microstructures were investigated. Among established isotherm equations, the Dubinin-Radushkevieh equation showed the best agreement with the experimental data, while the Langmuir equation showed a large deviation when employed at low relative pressures. The MP method, t-method and as-method were used to analyze the pore size distribution. The calculated average pore widths and BET （Brunauer-Emmett-Teller） surface areas for the sample A-13 were 0.86 nm and 1 286.60 m^2/g, while for the sample A-16, they were 0.82 nm and 1 490.64 m^2/g. The sample with larger pore width was more suitable to be used as additive in chemical heat pumps, while the other one could be used as adsorbent in adsorption refrigeration systems .