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Desorption of TEDA from impregnated charcoals

Conference ·
OSTI ID:6767023
Triethylenediamine (TEDA) is one of the most effective charcoal impregnants for trapping organic forms of radioiodine from air. It is used in air cleaning adsorbers, air samplers, and air purifying respirator canisters and cartridges for airborne radioiodine. Volatility of the pure crystals suggested the possibility of significant TEDA desorption in these applications, resulting in toxic levels of amine and/or degradation of sorbent efficiency. Measurements of TEDA desorption rates were made for four commercial charcoals. Temperatures of 70 to 120/sup 0/C were used to give levels detectable with a photoionization detector. Extrapolations to temperatures nearer normal ambient were made by using Clapeyron equation plots. Among three charcoals with the same 5% level of TEDA impregnation, desorption rates varied over factors as great as 10. Slopes of Clapeyron plots were similar, giving an average 25 kcal/mol heat of desorption. This corresponds to a doubling of the TEDA desorption rate with each 5/sup 0/C (9/sup 0/F) rise in temperature. Desorption rates were directly proportional to airflow rates or velocities through the test beds and independent of humidity. Desorption rates per unit weight of charcoal decreased exponentially with bed depth, presumably due to TEDA readsorption. Calculations based on this data and the geometry of a standard adsorber cell showed that at normal ambient temperatures: (1) concentrations of TEDA in effluent air are well below expected toxic levels; and (2) losses of TEDA may be significant. At elevated temperatures TEDA desorption rates are high enough to affect methyl iodide trapping efficiencies and, possibly, charcoal ignition temperatures.
Research Organization:
Los Alamos Scientific Lab., NM (USA)
DOE Contract Number:
W-7405-ENG-36
OSTI ID:
6767023
Report Number(s):
LA-UR-80-3432; CONF-801038-19
Country of Publication:
United States
Language:
English

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54 ENVIRONMENTAL SCIENCES
ADSORBENTS
ADSORPTION
AMINES
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CHARCOAL
DAYS LIVING RADIOISOTOPES
DESORPTION
HALOGENATED ALIPHATIC HYDROCARBONS
INTERMEDIATE MASS NUCLEI
IODINATED ALIPHATIC HYDROCARBONS
IODINE 131
IODINE ISOTOPES
ISOTOPES
MANAGEMENT
MEDIUM TEMPERATURE
METHYL IODIDE
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
ORGANIC IODINE COMPOUNDS
PROCESSING
RADIOACTIVE WASTE PROCESSING
RADIOISOTOPES
SORPTION
SORPTIVE PROPERTIES
SURFACE PROPERTIES
WASTE MANAGEMENT
WASTE PROCESSING