Adsorption of Radon and Water Vapor on Commercial Activated Carbons

Abstract

Equilibrium adsorption isotherms are reported for radon and water vapor on two commercial activated carbons: coconut shell Type PCB and hardwood Type BD. The isotherms of the water vapor were measured gravimetrically at 298 K. The isotherms of radon from dry nitrogen were obtained at 293, 298, and 308 K while the data for the mixture of radon and water vapor were measured at 298 K. The concentrations of radon in the gas and solid phases were measured simultaneously, once the adsorption equilibrium and the radioactive equilibrium between the radon and its daughter products were established. The shape of the isotherms was of Type III for the radon and Type V for the water vapor, according to Brunauer's classification. The adsorption mechanism was similar for both the radon and the water vapor, being physical adsorption on the macropore surface area in the low pressure region and micropore filling near saturation pressure. The uptake capacity of radon decreased both with increasing temperature and relative humidity. The heat of adsorption data indicated that the PCB- and the BD-activated carbons provided a heterogeneous surface for radon adsorption. The equilibrium data for radon were correlated with a modified Freundlich equation.     

Water Vapor Adsorption and Desorption on Materials Hydrothermally Solidified from Clay Minerals

Water vapor isotherms were examined and ¹H-magic-angle spinning nuclear magnetic resonance (¹H-MAS NMR) analysis was conducted to determine the amount of water vapor adsorbed and desorbed on hydrothermally solidified materials derived from clay minerals. The amount of water vapor adsorbed and desorbed decreased with increasing mesopore volume of the materials, which disagreed with the estimation obtained using the Kelvin equation. Water vapor was physisorbed on alumina-like sites in the materials. An increase in the binding energy between water vapor and the materials led to an improvement in the water vapor adsorption–desorption properties of materials.     

乙醇-水体系在马铃薯粉吸附剂上的气相吸附过程研究

利用固定床吸附柱(φ25 mm×900 mm)对乙醇-水体系在马铃薯粉吸附剂中的气相吸附过程进行了研究,研究了不同条件下乙醇-水体系在马铃薯粉中吸附的透过曲线。结果表明,在本试验条件下,生产能力和透过时间随温度降低、粒径变小、进料流量降低和床层高度增加而增大。在乙醇-水体系进料流量为3 mL/min左右、床层温度80℃、吸附剂粒径245～350μm、床层高度700 mm和进料乙醇体积分数94.5%条件下,每1 000 g马铃薯粉吸附剂可脱水得到无水乙醇205.1 g。马铃薯粉吸附性能良好,再生容易,具备作为生物质吸附剂制备无水乙醇的潜力。     

Binary Adsorption of n‐Butane or Toluene and Water Vapor

To clean the air in cars of noxious gases by adsorption, predominantly activated carbon is used. The height of the activated carbon layer is especially small in cabin air filtration. As test substances for adsorptive filters in cabin air filtration, toluene and n‐butane are prescribed in several engineering standards, e.g., ISO TS 11155‐2. In the study presented, the differences in binary adsorption between toluene or n‐butane and water vapor are investigated with emphasis on adsorption equilibrium and kinetics at temperatures between 15 °C and 33 °C, and relative humidity varying between 0 % and 90 %. The range of input concentrations is from 2 ppm_V up to 80 ppm_V.     

Synthesis of Super-Microporous Aluminosilicate Having Excellent Water Vapor Adsorption Property as an Adsorbent for an Adsorption Heat-Pump

The synthesis of super-microporous aluminosilicate with a pore diameter of 14.6 Å has been achieved, by means of synthesis under specified conditions with a skeletal material comprising TMOS and a small quantity of sodium aluminate, and a conventional alkyl-trimethylammonium halide (C₁₀TMABr) as a template. This super-microporous aluminosilicate has an adsorption capacity of 0.2 ml/g at a relative water vapor pressure of 0.2, and thus is promising as an adsorbent for an adsorption heat-pump.     

水蒸气透过率、透过量与透过系数的应用

详细介绍了3项透湿性参数——水蒸气透过率、透过量和透过系数的定义、应用范围以及相互之间的差异和换算关系,同时对于目前国际国内标准中定义不清晰的情况给予了说明。     

Methanol Vapor Adsorption on Silica and Soda-Lime-Silica Glass

Methanol vapor adsorption isotherms on vitreous silica and soda-lime-silica glasses were measured by gas chromatography in the low-pressure region of the physical adsorption isotherms after the adsorbents had been degassed in a dry atmosphere at successively higher temperatures. The isosteric heats of adsorption indicate that after strong degassing treatments each methanol molecule is adsorbed by the formation of a single hydrogen bond with the surface, but after low-temperature degassing more than one hydrogen bond is formed for each adsorbed molecule.     

Experimental Investigation and Modeling of Adsorption of Water and Ethanol on Cornmeal in an Ethanol‐Water Binary Vapor System

The adsorption capacity of water and ethanol on cornmeal in an ethanol‐water binary vapor system was investigated in a fixed‐bed apparatus for ethanol dehydration. Experiments were performed at temperatures of 82–100 °C for different relative humidities of ethanol‐water vapor. Adsorption equilibrium models, including those based on the adsorption potential theory of Polanyi and Sircar's model, have been used to fit the experimental data for water adsorption on cornmeal, and all gave good fits. For ethanol adsorption, pseudo‐equilibrium was defined as the mass adsorbed on the cornmeal within the time needed for the equilibrium for water on the same adsorbent. Based on this limiting condition, adsorption behaviors and mechanisms were analyzed.     

Leaching of E-Glass

The extraction of acid-soluble oxide constituents in E-glass fibers was studied as a function of acid strength and time. Leaching was found to be diffusion controlled. Surface area, moisture adsorption, and weight loss measurements show that the porous structure that results on leaching is controlled by acid strength and time. Polymerization occurring on leaching and aging accounts for structural changes in the porous product.     

水蒸气对MOFs材料吸附分离混合气影响的研究进展

实际工业过程中混合气的分离通常会受到水蒸气的影响,所以选择合适的固体吸附剂很重要。金属有机骨架(MOFs)材料是一类具有高比表面积、孔径可调等特点的新型材料。不同类型的MOFs材料与水的作用力不同,因此,水蒸气的存在对于该类材料的气体吸附和分离能力有着不同的影响。本文对近年来水蒸气对MOFs材料的气体吸附和分离影响的研究进行讨论。     

苯-水混合蒸气在活性炭上的二元吸附平衡

Adsorption equilibrium isotherms of benzene in the concentration range of 500-4000 mg·@m-3 on two commercial activated carbons were obtained using long-column method under 30℃ and different humidity conditions. Results show that the benzene and water vapors have depression effects upon the adsorption of each other and that the unfavorable effect of water vapor resembles its single-component isotherm on activated carbon. A competitive adsorption model was proposed to explore the depression mechanisms of the non-ideal, non-similar binary adsorption systems. A modified Polanyi-Dubinin equation was set up to correlate the binary adsorption equilibrium and to calculate the isotherms of benzene on activated carbon in presence of water vapor with considerable precision.     

Determination of Kinetics and Equilibria for Adsorption of Water Vapor on Single Zeolite Particles by a Magnetic Suspension Balance

In order to obtain kinetic and equilibrium data for the adsorption of water vapor on zeolite for use in packed bed adsorber simulations, experimental investigations have been conducted on single zeolite particles with the help of a magnetic suspension balance. The objective was, first, to present such data in a form that is accurate enough and as simple as possible for easier application of the packed bed model and, second, to investigate and discuss the potential of the magnetic suspension balance technique, comparing with more conventional methods.     

Effect of Organic Acids on E-Glass Fabric

E-glass fabric was treated with organic acids. Acid treatment leaches nonsiliceous ions from the glass structure via ion exchange. The degree of removal is determined by the strength of the acid and leaching time. The results, which are compared with those for mineral acids, show that the acid anion is involved in the leaching process.     

Water Adsorption on TiO2

Scanning Tunneling Microscopy (STM) studies and Density Functional Theory (DFT) investigations of the interaction of water with the rutile TiO₂ (110) surface are summarized. From high-resolution STM the following reactions have been revealed: water adsorption and diffusion in the Ti troughs, water dissociation in bridging oxygen vacancies, assembly of adsorbed water monomers into rapidly diffusing water dimers, and formation of water dimers by reduction of oxygen molecules. The STM results are rationalized based on DFT calculations, revealing the bonding geometries and reaction pathways of the water species on the TiO₂ (110) surface.     

缓冲吸附和变压吸附(PSA)系统油气回收技术研究

研究了双塔吸附对汽油储罐中挥发出油气的吸附效果,吸收剂采用硅胶和活性炭吸附。油气先经缓冲吸附系统,后经变压吸附处理。吸附剂在真空状态下,经新鲜空气吹扫作用下重生。在400kg吸附剂的PSA系统中,每小时可吸收20~46L汽油。排放气中,烃类体积浓度可达到低至0.01%。     

Effect of Water Vapor on Initial Sintering of Magnesia

The effects of water vapor on the initial sintering of magnesia powder compacts were studied from 800° to 1107°C. The magnesia was obtained by thermal decomposition of magnesium oxalate. Water vapor partial pressures from 8 × 10 ^–4 to 658 mm were used. Initial sintering occurred by a grain-boundary vacancy-diffusion mechanism with magnesium assumed to be the slow moving species. Increasing water vapor partial pressure increased sintering rates. A model based on the solubility of the hydroxide ion in MgO relates this increase to the increase in the cation vacancy concentration. The grain-boundary diffusion coefficient, D_G , varied with P _H2O. For partial pressures up to about 5 mm, n was approximately ½ and for partial pressures above 5 mm it was between 1.0 and 1.5. The activation energy for densification was 80 kcal/mole for partial pressures up to about 5 mm and 48 kcal/mole above this partial pressure.     

Effects of Water Vapor on Oxidation of Silicon Carbide

The rate of oxidation of silicon carbide was studied at different partial pressures of water vapor. The diffusion-rate constant was found to vary with the logarithm of the partial pressure of water vapor according to the theory of thin-film oxidation as proposed by Engell and Hauffe. The products of oxidation were cristobalite and tridymite, depending on the temperature. The diffusing species appeared to be the same in the presence of partial pressures of water vapor and in the presence of partial pressures of oxygen.     

Effect of Water Vapor on Dielectric Loss in MgO

A dielectric loss study of porous MgO indicates that H₂O absorption on MgO probably leads to the formation of surface defects as well as hydroxide ions. The ac conductivity, σ_ac followed the equation σ_ac=σ₁ + KP _H2O^0.27 from 550° to 800°C when the water partial pressure was varied between 7 × 10⁻⁵ and 3 × 10⁻² atm.     

Binary Adsorption Isotherms of Water and Ethyl Acetate Vapor for Materials Contained in a Box of a Tobacco Product

ABSTRACT

An experimental study has been carried out on the characteristics of binary adsorption isotherms of water and volatile flavor for typical materials used in a box of a tobacco product or cigarettes. Ethyl acetate chosen as a model for water–soluble volatile flavor. Binary adsorption isotherms for the tobacco, papers, filters, and activated carbons were measured with a flow–type multi–component adsorption system under the canstant conditions of temperature a t 303 K and vapor pressure of water a t 2.5 kPain the vapor pressure range of ethyl acetate from 0 to 4.2 kPa. A linear equation was applied to express the binary adsorption isotherms for the tobacco, papers and filters, while a Dubinin–Astakhov equation was applied for the activated carbons. The binary adsorption was characterized into three groups, depending on the selectivity as well as the mechanism of adsorption; i.e.(l) for tobacco and papers, water was adsorbed much greater rather than ethyl acetate, (2) for filters, ethyl acetate was adsorbed on the surface as great as water, (3) for activated carbons, ethyl acetate was adsorbed much greater onto their micropores rather than water. The results showed that ethyl     

Binary Adsorption Isotherms of Water and Ethyl Acetate Vapor for Materials Contained in a Box of a Tobacco Product

An experimental study has been carried out on the characteristics of binary adsorption isotherms of water and volatile flavor for typical materials used in a box of a tobacco product or cigarettes. Ethyl acetate chosen as a model for water-soluble volatile flavor. Binary adsorption isotherms for the tobacco, papers, filters, and activated carbons were measured with a flow-type multi-component adsorption system under the canstant conditions of temperature a t 303 K and vapor pressure of water a t 2.5 kPain the vapor pressure range of ethyl acetate from 0 to 4.2 kPa. A linear equation was applied to express the binary adsorption isotherms for the tobacco, papers and filters, while a Dubinin-Astakhov equation was applied for the activated carbons. The binary adsorption was characterized into three groups, depending on the selectivity as well as the mechanism of adsorption; i.e.(l) for tobacco and papers, water was adsorbed much greater rather than ethyl acetate, (2) for filters, ethyl acetate was adsorbed on the surface as great as water, (3) for activated carbons, ethyl acetate was adsorbed much greater onto their micropores rather than water. The results showed that ethyl