Dynamics Of Water Adsorption Research Articles

Effect of heat transfer on the transient dynamics of temperature swing adsorption process

The effect of radial heat transfer on temperature swing adsorption (TSA) was studied by using an air-drying TSA experiment. The experimental dynamics of water adsorption and thermal regeneration in a fixed bed packed with zeolite 13X were used to evaluate the predicted results from the developed models. One- and two-dimensional models for energy balance with various equations describing internal velocity were compared in terms of the prediction of transient dynamics of TSA. Since the heat effect in adsorption step depended on the isosteric heat of adsorption, a dynamic simulation was performed under adiabatic, near-adiabatic, and constant wall temperature conditions. A com- parison between one- and two-dimensional models was also made under near-adiabatic condition, which reflected on the experimental condition. There was little difference between adsorption breakthrough curves predicted by the one- and two-dimensional models because the radial distribution of temperature was negligible at the adsorption step. In the case of the regeneration step, a small difference between two models was expected just at the early period of time because the radial effect disappeared with time. One-dimensional model could provide an adequate prediction of the transient dynamics in this system when the wall energy balance was included.

Adsorption dynamics of water in layered bed for air‐drying tsa process

In this study, the dynamics of water adsorption and thermal regeneration in the zeolite 13X bed was compared with that in the layered bed with zeolite 13X and silica gel. Based on the breakthrough and regeneration dynamics, the two-bed, two-step TSA (thermal swing adsorption) process was simulated in both the zeolite 13X bed and the layered bed.

Clustered water adsorption on the NaCl(100) surface

The adsorption dynamics of water on NaCl(100) is studied by molecular dynamics calculations as a function of coverage. We find that, starting from a critical coverage of about 1/2 monolayer, a coupling of the water dipoles sets in and the interaction between the water molecules wins over the interaction between adsorbate and substrate leading via percolation to formation of infinite cluster networks. This effect is confirmed qualitatively by surface sensitive optical second harmonic measurements with well-controlled water exposure. At a coverage of one bilayer, a two-dimensional ‘‘ice’’ structure is found to be stable. Simulated low-energy electron diffraction (LEED) patterns for this configuration are in excellent agreement with recent observation of a c(4×2) overstructure.

Water vapor adsorption and desorption isotherms of biologically active proteins.

Using a protein isolated from soy, a dynamic water adsorption method was developed and the data were compared with those obtained from a static gravimetric procedure. Both methods gave comparable results, showing that Type II isotherms with considerable hysteresis were obtained. However, the dynamic procedure was preferred since it provided data rapidly and used significantly less material. Using the dynamic method, water adsorption isotherms at 25 degrees C were also determined for four biologically active proteins: alpha-amylase, beta-glucuronidase, lipase, and urease. BET (Brunauer, Emmet, and Teller) parameters were calculated and the specific surface areas for the native, biologically active proteins were found to be similar, 238.4 +/- 20.2 m2/g. On the other hand, the specific surface area for the denatured soy protein isolate was 144.6 m2/g. Nevertheless, the heat of absorbance for all of the proteins examined was similar, suggesting that they have comparable degrees of hydrophilicity.

An examination of how exposure to humid air can result in changes in the adsorption properties of activated carbons

Dynamic water adsorption isotherms and methanol and hexane breakthrough curves have been measured for samples of ASC, BPL and 208A activated carbons under conditions appropriate to their use in vapor filters. The differences in performance between control and samples that had previously been exposed to air at RH 80% and 22°C is discussed in terms of surface oxidation. Comparison of the breakthrough of methanol vapor through samples of dry charcoal is a convenient way of monitoring surface changes.