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Title: Adsorption and desorption of noble gases on activated charcoal: I. sup 133 Xe studies in a monolayer and packed bed

Adsorption and desorption of noble gases on activated charcoal: I. sup 133 Xe studies in a monolayer and packed bed Detailed desorption studies using petroleum-based activated charcoals were conducted in monolayers and packed beds. Less extensive studies were conducted on several other types of charcoal. Kinetic studies, using {sup 133}Xe, demonstrated the existence of a micropore volume with entrance capillaries that together determined the response characteristics of charcoal to external concentration gradients of tracer gases. This new two-phase model, composed of micropores and entrance capillaries, describes the desorption dynamics of an adsorbed gas in the presence of water vapor. Condensed water vapor in the entrance capillaries of the charcoal reduced the effective pore radius and increased the diffusion half-time. Water could also adversely affect the integrating capability of the charcoal dramatically if the adsorbed water completely blocked the entrance capillaries. The amount of adsorbed water required to block the capillaries varied with the charcoal type and was termed here as the break-point. The desorption parameters measured in this work can be used to design an improved passive Rn monitor to effectively integrate during a 3-7 d exposure period by eliminating the adverse effects of water vapor. The improved canister design would provide more accurate and reproducible measurements of indoor Rn concentrations than are currently available.
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Publication Date:
OSTI Identifier:6513519
Resource Type:Journal Article
Data Type:
Resource Relation:Journal Name: Health Physics; (USA); Journal Volume: 59:4
Country of Publication:United States
Language:English
Subject: 54 ENVIRONMENTAL SCIENCES; RADIATION MONITORS; DESIGN; RADON; RADIATION MONITORING; ACTIVATED CARBON; ADSORPTION; DESORPTION; INDOOR AIR POLLUTION; PACKED BED; RADIOECOLOGICAL CONCENTRATION; XENON 133; ADSORBENTS; AIR POLLUTION; BETA DECAY RADIOISOTOPES; BETA-MINUS DECAY RADIOISOTOPES; CARBON; DAYS LIVING RADIOISOTOPES; ECOLOGICAL CONCENTRATION; ELEMENTS; EVEN-ODD NUCLEI; FLUIDS; GASES; INTERMEDIATE MASS NUCLEI; INTERNAL CONVERSION RADIOISOTOPES; ISOMERIC TRANSITION ISOTOPES; ISOTOPES; MEASURING INSTRUMENTS; MONITORING; MONITORS; NONMETALS; NUCLEI; POLLUTION; RADIOISOTOPES; RARE GASES; SORPTION; XENON ISOTOPES 540130* -- Environment, Atmospheric-- Radioactive Materials Monitoring & Transport-- (1990-)