Scarpitta S C
Environmental Measurements Laboratory, U.S. Department of Energy, New York 10014-3621, USA.
Health Phys. 1996 May;70(5):673-9. doi: 10.1097/00004032-199605000-00008.
A new commercially available beaded carbon molecular sieve sorbent, Carboxen-564 (20/45 mesh), was tested and compared to Calgon-PCB (40/80) activated carbon for its adsorptive and desorptive characteristics under controlled conditions of temperature (25 degrees C) and relative humidity (RH). The amount of water vapor adsorbed by the beaded carbon molecular sieve material was typically a factor of 4 lower than the activated carbon, with a concomitant fourfold increase in the 222Rn adsorption coefficient, K(Rn). The maximum K(Rn) value for a thin layer of Carboxen-564, following a 2-d exposure at 40% RH, was 7.2 Bq kg(-1) per Bq m(-3). The K(Rn) or a 1-cm bed, following a 2-d exposure was 5.5 Bq m(-3), a 25% reduction. Under dynamic sampling conditions, where 0.4 g of the beaded carbon molecular sieve was contained in a 6 cm x 0.4 cm diameter tube, the maximum K(Rn) value was 6.5 Bq m(-3) after 2.5 h of sampling at 29% RH when the input flow rate was 4.2 x 10(-3) m3 h-1. Kinetic studies were also conducted under passive sampling conditions. The data show that the 222Rn buildup time-constant for a thin layer of the beaded carbon molecular sieve material was 1.3 h, whereas that of a 1 cm bed was 13 h. The 222Rn desorption time-constants, from gram amounts of the beaded carbon molecular sieve material into air and into a commercially available toluene based liquid scintillation cocktail, were 2 h and 3 h, respectively. Carboxen's high 222Rn adsorbing capacity, rapid kinetics, hydrophobicity and physical properties makes it an attractive alternative to other commercially available activated carbon used in passive and dynamic sampling devices.
一种新的市售珠状碳分子筛吸附剂Carboxen - 564（20/45目），在温度（25℃）和相对湿度（RH）可控的条件下，对其吸附和解吸特性进行了测试，并与卡尔冈 - PCB（40/80）活性炭进行了比较。珠状碳分子筛材料吸附的水蒸气量通常比活性炭低4倍，同时222Rn吸附系数K(Rn)增加了四倍。在40%RH下暴露2天后，Carboxen - 564薄层的最大K(Rn)值为每Bq m(-3) 7.2 Bq kg(-1)。暴露2天后，1厘米床层的K(Rn)为5.5 Bq m(-3)，降低了25%。在动态采样条件下，当输入流速为4.2×10(-3) m3 h-1时，在29%RH下采样2.5小时后，6厘米×0.4厘米直径管中含有0.4克珠状碳分子筛的最大K(Rn)值为6.5 Bq m(-3)。还在被动采样条件下进行了动力学研究。数据表明，珠状碳分子筛材料薄层的222Rn积累时间常数为1.3小时，而1厘米床层的为13小时。从克量的珠状碳分子筛材料向空气和市售甲苯基液体闪烁鸡尾酒中解吸222Rn的时间常数分别为2小时和3小时。Carboxen的高222Rn吸附能力、快速动力学、疏水性和物理性质使其成为被动和动态采样装置中使用的其他市售活性炭的有吸引力的替代品。
