Adsorption Isotherm Model for Analyzing the Adsorption Characteristics of Water Vapor to Commercially Available Silica Gel Adsorbents for Adsorption Desalination Applications

Tritium release in nuclear fusion power plants must be recovered as efficiently as possible in air cleanup system (ACS). In conventional ACS, the tritium gas is oxidized by catalysts, and then tritiated water vapor is collected by adsorbents, whereas which has a problem related to large ventilation force required to overcome high pressure drop in catalyst and adsorbent beds. Honeycomb-type catalyst and adsorbent offer a useful advantage in terms of their low-pressure drop, and honeycomb-type adsorbent using sepiolite-binder is feasible ability for application of ACS. In this study, we examined adsorption characteristics of water vapor on the building material, zeolitic materials using sepiolite-binder, for honeycomb-type adsorbent by changing temperature and concentration of water vapor, in comparison with those for conventional pebble-type adsorbent, and the experimental data were evaluated using Langmuir and Freundlich isotherm models. Each type of adsorbent includes mainly zeolite-4A. Adsorption capacity of zeolitic materials for both adsorbents gradually decreased with decreasing partial pressure of water or increasing temperature, and experimental data are found to fit Langmuir than Freundlich. The maximum adsorption capacity of water vapor on zeolitic material for honeycomb-type adsorbent, which was calculated by Langmuir isotherm model, is comparable to that for pebble-type adsorbent, and heat of water adsorption on zeolitic material for honeycomb-type adsorbent was higher than that for pebble-type adsorbent. These results indicate that honeycomb-type adsorbent using sepiolite-binder is applicable to ACS.

This research proposes a new isotherm model that is derived for adsorption of clustering and condensable vapors on mesoporous ceramics. The adsorption characteristics of water vapor on both experimental data and isotherm model were investigated over the relative pressure ranging from 0 to 0.95. The applicability of the model was evaluated by significance of fitting parameters. For each adsorption isotherm there are five parameters (m, qf, Kf, qm and Km). The comparison of modeling fit with experimental data was used as the methodology for selecting the most informative and the best-fitting model. The experimental testing results showed that this model is able to describe all possible behaviors of the water adsorption isotherm displaying type IV classification. The model is based on the forming and growth of the water molecule clusters and capillary condensation mechanism in mesopore. The findings suggest a significant tool for understanding the behavior of water adsorption in humidity-control porous ceramics.

Adsorption characteristics of water vapor on ferroaluminophosphate for desalination cycle

Adsorption characteristics of water vapor on the hypercrosslinked polymeric adsorbent

Adsorption Characteristics of Water and Silica Gel System for Desalination Cycle Oscar Rodrigo Fonseca Cevallos An adsorbent suitable for adsorption desalination cycles is essentially characterized by a hydrophilic and porous structure with high surface area where water molecules are adsorbed via hydrogen bonding mechanism. Silica gel type A++ possesses the highest surface area and exhibits the highest equilibrium uptake from all the silica gels available in the market, therefore being suitable for water desalination cycles; where adsorbent’s adsorption characteristics and water vapor uptake capacity are key parameters in the compactness of the system; translated as feasibility of water desalination through adsorption technologies. The adsorption characteristics of water vapor onto silica gel type A++ over a temperature range of 30 C to 60 C are investigated in this research. This is done using water vapor adsorption analyzer utilizing a constant volume and variable pressure method, namely the Hydrosorb-1000 instrument by Quantachrome. The experimental uptake data is studied using numerous isotherm models, i. e. the Langmuir, Toth, generalized Dubinin-Astakhov (D-A), Dubinin-Astakhov based on pore size distribution (PSD) and Dubinin-Serpinski (D-Se) isotherm for the whole pressure range, and for a pressure range below 10 kPa, proper for desalination cycles; isotherms type V of the International Union of Pure and Applied Chemistry (IUPAC) classification were exhibited. It is observed that the D-A based on PSD and the D-Se isotherm models describe the best fitting of the experimental uptake data for desalination cycles within a regression

Adsorption characteristics of water vapor on Li 2ZrO 3

Effect of the pore structure characteristics of coal samples on the dynamic adsorption of water vapor

Characterization of silica gel-based composites for adsorption cooling applications

Activated carbons have both hydrophilic surface oxygen functional groups, which act as primary adsorption centers for water vapor, and hydrophobic graphene layers on which nonpolar species are primarily adsorbed. The aim of this research was to investigate the effects of oxygen surface functional groups, in activated carbons, on the adsorption characteristics of water vapor. Activated carbon G was oxidized using nitric acid and then heat treated in the range 387-894 K to produce a suite of adsorbents with varying oxygen contents in the range 0.4-21.5 wt % daf, but very similar porous structure characteristics, thereby minimizing effects due to changes in porous structure. The type and concentration of surface oxygen groups present in each sample were assessed using TPD, FTIR, Boehm titration, and analytical methods. Water vapor adsorption at low relative pressure was dramatically enhanced by the presence of functional groups, in particular, carboxylic groups. Kinetic profiles for each pressure increment were modeled using a set of nested kinetic models, which allow the adsorption kinetics to be analyzed in relation to the adsorption mechanism. Relationships between water adsorption kinetics at low surface coverage and the type and concentration of oxygen surface functional groups were observed. A two component double exponential kinetic model was used when carboxylic groups were present in significant amounts with a slow kinetic component associated with adsorption on these groups. In the case of carbons where carboxylic groups were only present in, at most, relatively small amounts, a stretched exponential kinetic model was used and the rate constants in the low-pressure region decreased linearly with increasing Henry's Law constant and oxygen content. The results indicate the importance of adsorbate-adsorbent interactions in water adsorption kinetics and are consistent with a site-to-site hopping mechanism between functional groups.

At present, research on the influence of water on the physical properties of rocks is mostly focused on the macroscopic angle. Studies on nanoscale pore structure changes caused by water are few. Shale is characterized by good pore structure and high content of hydrophilic clay minerals susceptible to water. Based on this, in this paper the shale samples were obtained from underground layers 3000 m deep in Songliao Basin, Jilin Province, China. The sample parameters are measured by steam adsorption and nitrogen adsorption experiments under different soaking time conditions. The study shows that the pore structure of shale depends mainly on mineral composition and soaking time. With increase in soaking time, the amount of water vapor adsorption first decreases by 10% and then gradually increases. With water migration in the rock some pore structures are filled with shale particles. As the bubble time increases, the ion diffusion causes development of new pores and micro-cracks, and the adsorbed water vapor amount increases. At the microscopic scale, it is of great practical significance to study the nanoscale pore structure and adsorption characteristics of water vapor in the soft for different soaking time, and to further explore the stress characteristics, adsorption law, and gas migration in shale.

Adsorption characteristics of water vapor on honeycomb adsorbents

It is necessary to recover or process tritiated species that are extensively coexistent in nuclear fusion installations. A conventional way to recover tritium release to atmosphere is catalytic oxidation of tritiated species and adsorption of tritated water vapor on adsorbents with high surface areas. However, pressure loss would become more serious with increase in the size of adsorbent beds, which could lead to greater power needs for ventilation systems. Therefore, new adsorbents with low pressure loss and high surface areas need to be developed and utilized for such large-scale adsorption systems. Thus, the authors tested new types of adsorbents, which are gear-type and honeycomb-type pellet adsorbents. The experimental results reveal that the gear-type pellet adsorbents have larger adsorption capacity than the honeycomb-type pellet adsorbent. It was also found that the gear-type MS4A adsorbent possesses larger adsorption capacity than other adsorbents tested in this work. Furthermore, it was found that new types of adsorbents are lower pressure than conventional-type of adsorbents. Among the new adsorbents studied in this work, the gear-type MS4A adsorbent appears to be most promising for the application to the adsorption systems in terms of adsorption capacity and adsorption rate.

Adsorption Characteristics of Water Vapor on Sodium Chloride

The zeolite-filled membranes were made by a casting technique using polybutadiene and polydimethylsiloxane as the membrane material. The relationship between the dispersion state of zeolite in the membrane and the adsorption characteristics of water vapor were discussed. As the results, the equilibrium amount of water vapor adsorbed on zeolite in the membrane was approximately one-half the amount adsorbed on zeolite only. The adsorption rate of water vapor was dependent on the dispersion state of zeolite, the thickness of the membrane and the kinds of the membrane material. The modified particle-membrane diffusion model to describe the dispersion state of zeolite was presented on the basis of the transport through the membrane.

Measurement of adsorption characteristics of water vapor on medium- and low-rank coals and its influencing mechanism