Adsorption Isotherms,Kinetics, and Desorption of 1,2-Dichloroethane on Chromium-Based Metal Organic Framework MIL-101

Adsorption equilibrium and kinetics of 1,2-dichloroethane on a chromium-based metal-organic framework MIL-101 were studied. Desorption activation energies of 1,2-dichloroethane on the MIL-101 were measured using temperature program desorption (TPD) experiments. Results showed that the adsorption capacity of the MIL-101 for 1,2-dichloroethane is 19 mmol/g at 288 K, being much higher than those of some activated carbon, zeolite, and MWCNTs. The isotherms of 1,2-dichloroethane were well fitted by the Langmuir equation. The isosteric heat and diffusion coefficients of 1,2-dichloroethane adsorption on the MIL-101 were separately within the range of 42.0–61.6 kJ/mol and range of 0.854–2.246 × 10^?10 cm²/s. TPD spectra exhibited two types of adsorption sites on the MIL-101 with desorption activation energy of 48.6 and 87.6 kJ/mol separately. Multiple recycle runs of 1,2-dichloroethane adsorption-desorption at 298 K (10 mbar for adsorption and 0.05 mbar for desorption) showed the 1,2-dichloroethane adsorption on the MIL-101 is highly reversible, and desorption efficiency is up to 98.42%.     

Adsorption of Chlorinated Hydrocarbon Pollutants on Silica Gel

Abstract

A survey of indoor air pollutants was conducted. The removal of six chlorinated hydrocarbons, including methyl chloride, methylene chloride, chloroform, carbon tetrachloride, 1,1,1-trichloroethane, and tetrachloroethylene was performed using adsorption methods. The equilibrium uptakes of the six indoor pollutants on silica gel were determined gravimetrically at 25°C and at pressures up to saturation. The modified potential theory proposed by Dubinin and coworkers was used to correlate the adsorption data.     

水中1,1,1-三氯乙烷的三种去除工艺方法

该文对水中1,1,1-三氯乙烷的三种去除方法进行了研究。结果表明曝气吹脱能有效去除水中1,1,1-三氯乙烷。当初始浓度为14 mg/L时,曝气流量越大,去除率越高,在固定的曝气流量下,曝气时间越长,去除效果越好,当曝气时间达到35 min时去除率达到100%;当气水比为3.5时,剩余污染物浓度可以满足国标限值要求;在相同的曝气流量下,1,1,1-三氯乙烷去除效果随着温度的升高而增大;pH值对1,1,1-三氯乙烷去除无影响。水源水条件下,当1,1,1-三氯乙烷初始浓度为1 mg/L、粉末活性炭投加量为20 mg/L、吸附时间为120 min时,1,1,1-三氯乙烷吸附达到平衡,30 min去除率达42%。1,1,1-三氯乙烷初始浓度为5 mg/L,煮沸,2 min后即可达到国标限值以下,5 min后去除率可达80%。     

Dynamic Analysis of Diffusion and Adsorption of Water‐Miscible and Water‐Immiscible Organic Vapors in Soil

A dynamic analysis of the diffusion and adsorption of water‐miscible volatile organic compounds (methanol and acetone) and water‐immiscible volatile organic compounds (benzene and toluene) in a soil pellet has been performed experimentally by using the single pellet moment technique. The experiments were conducted in a one‐sided single pellet adsorption cell at a temperature of 30 °C and varying relative humidities (0, 20, and 40 %). The results obtained with dry and wet systems showed that volatile organic tracers were adsorbed reversibly onto the soil. The overall adsorption equilibrium constants of both water‐miscible and water immiscible volatile organic compounds decreased with relative humidity. The sorption of water‐immiscible VOCs (benzene) onto soil was found to be much less than that of water‐miscible VOCs (methanol). The effective diffusivity of water‐immiscible volatile organic vapor (benzene) in the soil did not show a considerable change with relative humidity. In contrast, there was an appreciable change in the effective diffusivity for water‐miscible VOCs (methanol) with moisture.     

BUBBLE TEMPERATURE MEASUREMENTS ON THE BINARY MIXTURES FORMED BY 1,2-DIMETHYLBENZENE WITH SOME CHLOROETHANES AND CHLOROETHYLENES AT 95.8 KPA

Bubble temperatures at 95.8?kPa over the entire composition range were measured for the binary mixtures formed by 1,2-dimethylbenzene with 1,2,-dichloroethane, 1,1,1-trichloroethane, 1,1,2,2-tetrachloroethane, trichloroethylene, and tetrachloroethylene using a Swietoslawski type ebulliometer. The liquid phase composition versus temperature measurements are accurately represented by the Wilson model.     

Bubble Temperature Measurements On The Binary Mixtures Of sec-butanol With Chloroethanes And Chloroethylenes At 94.6kpa

Bubble point temperatures at 94.6 kPa over the entire composition range are measured for the binary mixtures formed by sec-butanol with 1,2,-dichloroethane, 1,1,1,-trichloroethane, 1,1,2,2-tetrachloroethane, trichloroethylene, and tetrachloroethylene, making use of a Swietoslawski-type ebulliometer. The liquid phase composition versus temperature measurements are found to be well represented by the Wilson model.     

用单颗粒色谱法测定颗粒内的各种速率参数——(Ⅱ)CO变换反应动力学参数的测定

运用统计矩理论推导出催化剂颗粒内气体吸附常数、有效扩散系数和反应速率常数与实验矩之间的关联式.在常压及高至340℃的温度下,用常规的热导池鉴定器测定了Co在B110催化剂中的有效扩散系数、吸附平衡常数以及变换反应CO十H_2O=H_2十CO_2的反应速度常数.它为化学反应工程基础研究提供了一种新型的、有效实用的实验技术.     

活性炭对不同有机物吸附性能的影响

通过活性炭对不同分子结构的有机物一阳离子嫩黄和苯酚、不同水体环境中苯酚的吸附,以及对水源水中挥发性有机物和可提取有机物的吸附规律研究结果表明,活性炭对水体中有机物的吸附量不仅与有机物的分子结构有关,而且与水体中有机物种类的多寡有关,水体中的各种有机物在活性炭上存在竞争吸附,对于挥发性有机物,随分子量的增大,其在活性炭上的吸附量越大;而对可提取有机物,随分子量的增大,其吸附量反而减小。     

Mechanism of acetic acid transfer from aqueous sodium chloride solutions to some orgranic solvents

Salting out of acetic acid from aqueous solutions containing various concentrations of sodium chloride into some organic solvents has been studied at various temperatures. The solvents include cyclohexane, carbon tetrachloride, 1,2-dichloroethane, isopropyl ether, 2-pentanone and 1-heptanol. The results are consistent with a transfer mechanism involving monomer partitioning, dimerization and dimer return to the aqueous phase. Factors favoring monomer partitioning such as rise in both temperature and salt level retard dimer return, a process which is found to be significant in dimerization-enhancing solvents. The sensitivity of various solvents towards salt effect increases in the order 1-heptanol < isopropylether < 1,2-dichloroethane < 2-pentanone < cyclohexane < carbon tetrachloride which generally parallels in the reverse order the extent of stabilization of the acid by various solvent interactions.     

ADSORPTION EQUILIBRIUM OF CARBON TETRACHLORIDE ON DRY SOILS

Vapor phase adsorption equilibrium of carbon tetrachloride, a priority pollutant, on dry soils was studied at 288, 293, and 298 K. Using a gravimetric adsorption apparatus, adsorption /desorption isotherms of carbon tetrachloride were generated on two different soil samples. The effects of temperature and soil characteristics were examined. Isosteric heals of adsorption were calculated and heat curves were constructed.

Adsorption isotherms of carbon tetrachloride on dry soil samples were Type II, indicating formation of multilayers of adsorbate on the soil particle surface. Considerable hysteresis effects, associated with capillary condensation, were observed upon desorption. Thermal data confirmed that the adsorption of carbon tetrachloride vapor on soil was primarily physical adsorption. Heat curves showed that the soil samples had energetically heterogeneous surfaces. A positive correlation between The soil's specific surface area and its sorption capacity was observed. Clay content and pore size were also dominating factors.

The experimental data were correlated by the Polanyi Potential, the BET, and the GAB models in order to provide input lo fate and transport models predicting the degradation or movement of volatile organic pollutants in soil. The BET equation gave accurate data fit, within a deviation range of 2·63-5·40%, for up to 40% of the saturation pressure. The GAB equation provided superior fit of the data for the entire relative pressure range. Absolute error percentages from the GAB model ranged from 1·77 to 5·38%. Results followed the Potential Theory satisfactorily and led to a single temperature-independent characteristic curve.     

Investigation of the kinetics for the photosynthesis of methylchloroform

In this work the photochemical chlorination of 1,1-dichloroethane to 1,1,1-trichloroethane in the gas-phase is investigated. It can be shown, that in the analysis of this reaction system exponential equations for the reaction rates are in practice superior to equations based on mechanistical considerations. The use of lower reactant concentrations leads to higher selectivities for this reaction; quantum yields of 10⁴ and more permit the use of weak lamps.     

Utilization of mesoporous molecular sieves synthesized from natural source rice husk silica to Chlorinated Volatile Organic Compounds (CVOCs) adsorption

The adsorption of trichloroethylene (TCE), tetrachloroethylene (PCE), and carbon tetrachloride was studied over our synthesized mesoporous material, MCM-41, from rice husk silica source, abbreviated as RH-MCM-41. More than 99% silica for RH-MCM-41 synthesis was extracted from rice husk under refluxing in HBr solution and then calcined at 873 K for 4 hours. RH-MCM-41 possessed surface area around 750-1,100 m²/g with a uniform pore size with an average diameter of 2.95 nm, narrow range of pore distribution and somewhat hexagonal structure, similar to properties of parent MCM-41. The adsorption of CC1₄ to RH-MCM-41 was stronger than that of TCE and PCE. The adsorption capacity of RH-MCM-41 for CVOCs (chlorinated volatile organic compounds) was higher than commercial mordenite and activated carbons.     

REMOVAL OF TOLUENE AND DICHLOROMETHANE FROM AQUEOUS PHASE BY GRANULAR ACTIVATED CARBON (GAC)

Chlorinated hydrocarbons and aromatics constitute the major class of volatile organic compounds that contaminate groundwater. In this study, the equilibrium uptake and column dynamics for the adsorption of dichloromethane (as a typical chlorinated hydrocarbon) and toluene (as a representative of aromatic compounds) from aqueous phase on coal-based granular activated carbon (GAC) were investigated. The adsorption isotherms were measured in a temperature range of 20–40°C. The experimental data obtained were correlated with several adsorption isotherm models. The Langmuir model was well adapted to describe the dichloromethane adsorption on GAC, while the adsorption of toluene on GAC was found to be well described by the Langmuir-BET hybrid model in the stated temperature range with R-squared value of about 0.99. The variations in adsorption breakthrough curves of toluene and dichloromethane with respect to operational parameters such as initial concentration, flow rate, column length, and temperature were investigated. The experimental breakthrough curves of both adsorbates are well fitted by Yan's model with high accuracy (R-squared value of 0.98–99) in most cases.     

Greenhouse Gas Adsorptivity of Horn-Shaped Carbon Nanotubes over Nitrogen: Equilibrium Study

The synthesis of horn-shaped carbon nanotubes using carbon tetrachloride as carbon source was carried out by solvothermal method at 200°C for 2 h. The scanning and transmission electron microscopic characterization of the obtained product showed the formation of horn-shaped carbon nanotubes with irregular wall structure having inner diameter of ～105 nm and length of ～1 µm. The equilibrium gas adsorption properties of horn-shaped carbon nanotubes derived from carbon tetrachloride were successfully investigated for CO₂, CH₄, and N₂ at 288, 303, and 318 K. Horn-shaped carbon nanotubes possess better CO₂ adsorption capacity (2.53 mmol/g) with high capacity selectivity (14.7) and equilibrium selectivity (59.1) over N₂ at 288 K. The detailed adsorption study with estimation of physical parameters such as Henry's constant and heat of adsorption identifies the horn-shaped carbon nanotubes as a potential adsorbent material in the field of CO₂ storage and separation.     

ADSORPTION OF AUTOMOTIVE PAINT SOLVENTS ON ACTIVATED CARBON: III. EQUILIBRIUM ADSORPTION OF BINARY MIXTURES

The use of activated carbon adsorption systems to remove volatile organic compounds released during automobile paint spray operations has received considerable attention in the past few years. In this paper, adsorption equilibria of eight automotive paint solvent pairs on activated carbon are presented. The data were obtained at total vapor concentrations of 365 ppm by volume, typical of those found in automobile assembly plant spraybooth exhaust air. Correlations of the data using two different modifications of the Polanyi adsorption potential theory in order to accommodate multicomponent equilibria are also presented and discussed. The correlations evaluated predict equilibrium compositions reasonably well for some binary mixtures. However, neither of the methods evaluated appeared to be satisfactory to correlate the equilibrium composition of all of the vapor pairs studied. A possible explanation for this behavior is that very small errors in the data available for the adsorption of pure components result in substantial changes in the predicted binary mixture compositions.     

1,1,2-三氯乙烷生产工艺的研究进展

1,1,2-三氯乙烷在化学工业中十分重要,可以用来作溶剂、萃取剂、杀虫剂,并且可以用于医学领域起麻醉作用,也可以是制作修正液的原料以及用来生成1,1-二氯乙烷。综述了氯乙烯氯化法、塔式合成法、1,2-二氯乙烷反应精馏法、利用烯烃混合废气法、共沸精馏法等1,1,2-三氯乙烷的生产方法。     

Structure and adsorption properties of activated carbon aerogels

Activated carbon aerogels (ACAs) with excellent microporosity (e.g., 0.44 cm³/g) and mesoporosity (e.g., 1.72 cm³/g) were prepared by CO₂ activation. Their structures were investigated with transmission electron microscopy and N₂ adsorption–desorption analysis. Subsequently, their adsorption properties toward organic vapors were studied with static and dynamic adsorption experiments. The micropores of the ACAs had stronger adsorption ability than those of normal porous carbons. Furthermore, the condensation of organic vapors in the mesopores of ACAs greatly enhanced their equilibrium adsorption at high relative pressures. As a result, the adsorption capacities of organic vapors on the typical ACAs prepared were about 2–3 times greater than those on normal porous carbons. In addition, they also possessed excellent adsorption dynamics and outstanding desorption and regeneration properties. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Sorption and diffusion of volatile organic compounds in polydimethylsiloxane membranes

Sorption and diffusion of ethanol, 1,1,1-trichloroethane (TCA), and trichloroethylene (TCE) were investigated in polydimethylsiloxane (PDMS) membranes using a gravimetric technique. The thermodynamic equilibrium and kinetic properties were evaluated at temperatures of 25, 100, and 150°C. The sorption isotherms for TCA and TCE can be correlated well using the Flory-Huggins model. However, a three parameter Koningsveld-Kleinjtens variation to the Flory-Huggins equation is required for correlation of the ethanol isotherm. The solubility coefficients of TCA and TCE increase with activity, but it remains almost constant for ethanol. The calculated sorption energies reveal high positive heat of mixing for ethanol. TCA and TCE sorption in PDMS decreases strongly with temperature as opposed to ethanol. Clustering function analysis is used to explain the anomalous ethanol sorption and diffusion behavior in PDMS. TCA and TCE diffusivities do not exhibit large variations with volatile organic compound activity. However, ethanol demonstrates a maxima in its diffusivity at activities where it has minimum clustering tendencies. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 165–175, 1998     

Specific adsorption of tetraalkylammonium cations on the 1,2-dicloroethane/water interface

Interfacial tension was used to study the electrochemical properties of the interface between LiCl in water and tetraalkylammonium tetraphenylborate in 1,2-dichloroethane. The interfacial tension decrease with decreasing of the size of the cation of the organic supporting electrolyte on the order TBA⁺ < THA⁺ < THpA⁺ < TOA⁺. The decrease of interfacial tension is also observed at the electrocapillary maximum the potential of which (potential of zero charge) shift towards more positive values in the order TBA⁺ > THA⁺ > THpA⁺ > TOA⁺. This fact maybe an evidence that there is an increase of adsorption when the alkyl chain length of the organic cation is reduced.     

Heterogeneous Adsorption Characteristics of Volatile Organic Compounds (VOCs) on MCM‐48

Abstract

This work focuses on the fundamental studies of heterogeneous adsorption characteristics of mesoporous adsorbent. MCM‐48 was synthesized to investigate the adsorption properties of eight different volatile organic compounds (benzene, cyclohexane, n‐hexane, toluene, methanol, acetone, methyl ethyl ketone (MEK), and trichloroethylene (TCE)). The gravimetric method was used to measure the adsorption equilibrium amount. Several simple and reliable methods such as isosteric enthalpy of adsorption, thermodynamic properties, condensation pressure, organophilicity, and adsorption energy distribution were evaluated to understand the surface heterogeneity of the VOCs+MCM‐48 adsorption system. This work shows that the unique features of the VOCs+MCM‐48 adsorption system are highly dependent on the adsorption step, ionization potential, and Debye dipole moment of VOCs.