Most models for fixed bed adsorbers have used either the homogeneoussolid or pore diffusion model for the pellets. When the adsorption isotherm is linear, the two models can lead to identical breakthrough curves. The conditions for this equivalence are presented here. It is shown that one of the bulk flow factors that was included in the formulation of one pore diffusion model will be significant only for feedstreams containing a relatively high concentration of adsorbate. The prosity factor of the pore model is shown to be very important, especially as the porosity decreases. The importance of the two diffusional models with respect to the predicted breakthrough curves is demonstrated. For comparable beds, it is shown that the breakthrough curve based on the homogeneous model is delayed with respect to that based on the pore model at early times, regardless of the shape of the isotherm. Finally, the various possible solutions for an irreverisble isotherm are reviewed for each of the models, and a solution is presented for the general case of a pore model with an outside film resistance.

Pore and solid diffusion models for fixed-bed adsorbers

 Many atmospheric chemicals occur in the gas phase as well as in liquid cloud droplets and aerosol particles Therefore, it is necessary to understand the distribution between the phases According to Henry's law, the equilibrium ratio between the abundances in the gas phase and in the aqueous phase is constant for a dilute solution Henry's law constants of trace gases of potential importance in environmental chemistry have been collected and converted into a uniform format The compilation contains 17 350 values of Henry's law constants for 4632 species, collected from 689 references It is also available at http://wwwhenrys-laworg 

/pdf/compilation-of-henry-s-law-constants-version-4-0-for-water-58il9q0ogv.pdf

Compilation of Henry's law constants (version 4.0) for water as solvent

A review of the mechanisms of solute sorption onto various biosorbents has been performed. The mechanisms have been subdivided into reaction based systems and diffusion based systems and the literature has been reviewed in accordance with these two groups. The range of solute-sorbent systems reviewed include metal ions, dyestuffs and several organic substances in aqueous systems onto a wide range of biosorbents and mineral earths. Extensive tables are presented summarising isotherm types, sorption capacities, kinetic models which have been applied particularly to biosorbent systems but also to many other adsorbent materials.

http://dns2.asia.edu.tw/~ysho/YSHO-English/Publications/PDF/Sep%20Pur%20Met29,%20189.pdf

Kinetics of pollutant sorption by biosorbents: review

The preparation of ultrahydrophobic and ultralyophobic surfaces using several techniques is described. Plasma polymerization of 2,2,3,3,4,4,4-heptafluorobutyl acrylate on poly(ethylene terephthalate) yields surfaces with water contact angles of θA/θR = 174°/173°. Argon plasma etching of polypropylene in the presence of poly(tetrafluoroethylene) renders surfaces with water contact angles as high as θA/θR = 172°/169°. Surfaces of compressed pellets of submicrometer, variable-diameter spherical particles of PTFE oligomers exhibit water contact angles of θA/θR = 177°/177°, methylene iodide contact angles of θA/θR = 140°/138°, and hexadecane contact angles of θA/θR = 140°/125°. We emphasize that contact angle hysteresis is more important in characterizing lyophobicity than is the maximum achievable contact angle. These surfaces are rough at the micrometer and submicrometer scales, and water drops roll easily on all of them. We make an intuitive argument that the topology of the roughness is important and contr...

Ultrahydrophobic and Ultralyophobic Surfaces: Some Comments and Examples

Adsorptive removal of phenol by bagasse fly ash and activated carbon: Equilibrium, kinetics and thermodynamics

Binary Langmuir and Freundlich isotherms for ideal adsorbed solutions

Theory for Irreversible and Constant-Pattern Solid Diffusion

The composition of the vapor phase over sulfuric acid has not been measured experimentally because of the low volatility of H/sub 2/SO/sub 4/. A method is described for calculating the partial pressures of H/sub 2/O, H/sub 2/ SO/sub 4/, and SO/sub 3/ based upon liquid-phase partial-molal thermodynamic quantities. Tables and graphs are provided which give the above partial pressures from --50 to 400 deg C at thirty-six compositions between 10 and 100 weight-percent acid. (auth)

/pdf/vapor-liquid-equilibria-for-aqueous-sulfuric-acid-1fzuhw18q6.pdf

Vapor-liquid equilibria for aqueous sulfuric acid

In two-phase flow operations, longitudinal dispersion (or axial mixing) has an undesirable effect on equipment performance, especially if a high degree of completion is needed. Mathematical solutions are developed for general and specific cases of longitudinal dispersion accompanying mass transfer or heat transfer, calculated from a simplified diffusion model that assumes a mean longitudinaldispersion coefficient and a mean velocity for each phase. Concentrations within the equipment and at the outlet are shown to depend upon four dimensionless parameters. These are functions of the dispersion rates and velocities, the equilibrium partition coefficient, and the true'' overall mass- transfer coefficient. Based upon computed tables now available, graphs are included to show how the parameters are related. An empirical correlation is given for exterior apparent NTU,'' which serves as a useful design factor. (auth)

Theodore Vermeulen

Papers

Binary Langmuir and Freundlich isotherms for ideal adsorbed solutions

Theory for Irreversible and Constant-Pattern Solid Diffusion

Vapor-liquid equilibria for aqueous sulfuric acid

Longitudinal Dispersion in Two-Phase Continuous-Flow Operations

Multicomponent Ion Exchange in Fixed Beds. General Properties of Equilibrium Systems