Charcoal traps, activated

Helium [7440-59-7] M 4.0. Dried by passage through a column of Linde 5A molecular sieves and CaS04, then passed through an activated-charcoal trap cooled in liquid N2, to adsorb N2, argon, xenon and krypton. Passed over CuO pellets at 300° to remove hydrogen and hydrocarbons, over Ca chips at 600° to remove oxygen, and then over titanium chips at 700° to remove N2 [Arnold and Smith 7 Chem Soc, Faraday Trans 2 77 861 1981]. 

Air samples can be analyzed by passing a known volume of air through a Teflon filter to catch air particulates followed by an activated charcoal filter to trap any gas-phase materials. The Teflon filters are extracted with hexane, concentrated, and analyzed by GC/MS. The charcoal traps are desorbed with carbon disulfide, concentrated, and analyzed by GC/MS. No performance data were reported (Dannecker et al. 1990). 

The correct management of the various gaseous, liquid and solid wastes determines the regularity of production. The gaseous wastes flow through exhaust systems equipped with absolute filters and soda lime and activated charcoal traps. They are discharged into the atmosphere after analysis of their krypton 85 and iodine content. The liquid wastes from the various cells are stored in 1 nr tanks (located in Petrus) and removed periodically by a shielded tank truck for transport to a liquid waste treatment station in another C.E.A. center. 

Schlosser et al. (1984) modified this technique to make high precision measurements of Ra in seawater. They degassed the sample by boiling 14 L for 45 min and transferred the Rn into an activated charcoal trap at -78 °C. The charcoal trap was warmed to 450 °C and the Rn transferred into a proportional counter with a mixture of 90 % argon and 10 % methane. Details of the proportional counter and associated electronics are given in Schlosser et al. (1983). 

The sample is 100 cubic feet (STP) of air compressed into a bottle containing 100 cc STP of active krypton and 75 cc STP of active xenon. Average yields are about 90% for krypton and 95% for xenon. The time required for the separation is about 8 hours of which 3 hours are spent in bleeding the sample into the system. Before the run all charcoal traps have been heated to 350 C and pumped on until the thermocouple vacuum gauge in the manifold... 

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