On the physical adsorption of vapors by microporous carbons

Journal Article · Sat Dec 31 23:00:00 EST 1994 · Journal of Colloid and Interface Science; (United States)

DOI:https://doi.org/10.1006/jcis.1995.1018· OSTI ID:6604979

Bradley, R H ^[1]; Rand, B ^[2]

---

1. Univ. of Technology, Loughborough (United Kingdom). Inst. of Surface Science and Technology
2. Univ. of Leeds (United Kingdom). Division of Ceramics

The physical adsorption of nonpolar and polar vapors by active carbons is discussed in relation to pore structure and pore wall chemistry. For nonpolar vapors the Dubinin-Radushkevich equation is used to derive micropore volumes (W[sub 0]), average adsorption energies (E[sub 0]), and micropore widths (L) for a number of systems. These parameters are used to interpret the adsorption behavior of nitrogen which, because it is a relatively small molecule, is frequently used at 77 K to probe porosity and surface area. Results are presented for three carbons from differing precursors, namely, coal, coconut shells, and polyvinylidene chloride (PVDC) to illustrate the applicability of the technique. For the latter carbon increases in micropore size, induced by activation in carbon dioxide, and reductions in accessible pore volume caused by heat treatment in argon are also characterized and related to structural changes. The approach is then extended to the adsorption of larger hydrogen vapors, where the resulting W[sub 0] values may require correction for molecular packing effects which occur in the lower relative pressure regions of the isotherms, i.e., during the filling of ultramicropores. These packing effects are shown to limit the use of the Polanyi characteristic curve for correlating isotherm data for several vapors, of differing molecular size, by one adsorbent. Data for the adsorption of water, which is a strongly polar liquid, have been interpreted using the Dubinin-Serpinsky equation.

• OSTI ID: 6604979
• Journal Information: Journal of Colloid and Interface Science; (United States), Journal Name: Journal of Colloid and Interface Science; (United States) Vol. 169:1; ISSN 0021-9797; ISSN JCISA5
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
010500 -- Coal
Lignite
& Peat-- Products & By-Products
09 BIOMASS FUELS
099000 -- Biomass Fuels-- Products & By-Products-- (1990-)
36 MATERIALS SCIENCE
360602* -- Other Materials-- Structure & Phase Studies
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201 -- Chemical & Physicochemical Properties
ACTIVATED CARBON
ADSORBENTS
ADSORPTION ISOTHERMS
AGRICULTURAL WASTES
CARBON
CARBONACEOUS MATERIALS
CARBONIZATION
CHEMICAL ACTIVATION
CHEMICAL REACTIONS
COAL
DECOMPOSITION
ELEMENTS
ENERGY SOURCES
FLUIDS
FOSSIL FUELS
FUELS
GASES
ISOTHERMS
MATERIALS
MICROSTRUCTURE
NONMETALS
ORGANIC COMPOUNDS
ORGANIC POLYMERS
ORGANIC WASTES
POLYMERS
POLYVINYLS
PORE STRUCTURE
SORPTIVE PROPERTIES
SURFACE PROPERTIES
WASTES