P.T. John

Application of John's isotherm to predict the adsorption of a binary gas mixture from the adsorption of individual component gases

Abstract It is shown that one can predict the adsorption of a binary gas mixture from the adsorption of individual component gases by means of Johns isotherm. It is found that the slope and intercept of Johns adsorption isotherm for binary mixture is equal to mean of the slopes and intercepts of individual adsorption isotherms. The relation given by Lewis et al . may be used to prove the validity of the above method.

Micropore volumes of carbons by means of a new isotherm equation

Abstract The linearized form of the isotherm equation developed by John is given by log log P = C + n log v . The log v values corresponding to relative pressure 1, on the extrapolated straight line of the experimental plot of the above equation gave micropore volume in good agreement with the values obtained by Dubinin method, especially for microporous carbons giving Type 1 and extremely low pressure isotherms. It is shown mathematically that the new equation is fundamentally the same as Dubin equation.

The complete identity of the isotherm equations of dubinin and john for determination of the volume and degree of microporosity of carbon

Abstract Complete identity of adsorption isotherms of Dubinin and John is proved by showing that the slope D of Dubinin equation is equal to slope D0 of Dubinin type equation derived from Johns isotherm and also showing that the terms involved in D and D0 are fundamentally the same. It is shown that the degree of microporosity is proportional to n the slope of Johns isotherm. B the measure of microporosity in Dubinin equation is inversely proportional to n. The advantages of Johns isotherm are also given.

Characterization of structural parameters of porous materials by a new adsorption isotherm

A new adsorption isotherm equation, log logP=C+n logv, has been developed which characterizes many properties of the structure of porous materials, such as monolayer capacity of isotherms of Types I, II and IV, limiting micropore volume at extremely low pressure, degree and dispersion of micropores, mesopore surface area, mean pore size, etc. The equation has been successfully extended to binary and ternary mixtures, data for which have been obtained from the individual isotherms. It is also shown that a linear plot of the new isotherm implies that the distribution of adsorption volume with adsorption potential is Gaussian. Various other well know isotherm equations have been deduced from this new equation. The equation is direct and involves fewer mathematical calculations for solving the structural parameters of porous materials.

Determination of mesopore surface area in presence of micropores

A modified t-method known as tJ method, capable of finding mesopore surface area in absence or presence of micropores in which adsorption may be pressure dependent or pressure independent is described by the application of Johns adsorption isotherm equation.

A new criterion to determine the separation factor for the adsorption isotherm of a gas mixture

We show that the separation factor can be found by applying Johns adsorption isotherm of gas mixture

Determination of surface area/monolayer capacity or limiting micropore volume of carbons from binary and ternary mixtures

It is shown that one can predict the adsorption of binary and ternary mixtures in any percentage ratio from the adsorption of individual component gases by means of Johns isotherm equation. The surface area of mesoporous materials or the limiting micropore volume of microporous materials from binary and ternary mixture adsorption isotherms is given. The relation given by Lewis et al. may be used to prove the validity of the above method and determine the contribution of each component of the mixture.

Oil extrusion and constant pressure head methods to determine surface area of granular carbon powders

Abstract Surface area of granular powders such as carbon powders used in the manufacture of cinema arc carbon rods, brushes etc. was determined by the method of oil extrusion. The granular powder thoroughly dispersed in anthracene oil of density d was poured into a Buchner funnel to a few millimeters depth. An increasing suction pressure was applied till it reached the maximum possible value. Critical pressure pc at which rapid displacement of oil took place and v the volume of oil retained after complete extrusion of oil at pressure pc were observed and r the capillary radius corresponding to pc was determined. Then applying the above values of v and r in an empirical equation similar to Wickes equation, S the surface area was determined. The results were tested using Blaines method and constant pressure head apparatus designed by the authors.