title: Evaluation of radon adsorption characteristics of a coconut shell-based activated charcoal system for radon and thoron removal applications.
abstract: Radon ((222)Rn), thoron ((220)Rn), and their decay products contribute a major fraction (more than 50%) of doses received from ionisation radiation in public domain indoor environments and occupation environments such as uranium mines, thorium plants, and underground facilities, and are recognised as important radiological hazardous materials, which need to be controlled. This paper presents studies on the removal of (222)Rn and (220)Rn from air using coconut shell-based granular activated charcoal cylindrical adsorber beds. Experiments were conducted to evaluate the (222)Rn and (220)Rn adsorption characteristics, and the mitigation efficiency of coconut-based activated charcoal available in India. The performance parameters evaluated include breakthrough time (τ) and adsorption coefficient (K), and degassing characteristics of the charcoal bed of varying dimensions at different flow rates. While the breakthrough for (222)Rn occurred depending on the dimension of the adsorber bed and flow rates, for (220)Rn, the breakthrough did not occur. The breakthrough curve exhibited a stretched S-shape response, instead of the theoretically predicted sharp step function. The experiments confirm that the breakthrough time individually satisfies the quadratic relationship with respect to the diameter of the bed, and the linear relationship with respect to the length, as predicted in the theory. The K value varied in the range of 2.3-4.12 m(3) kg(-1) with a mean value of 2.99 m(3) kg(-1). The K value was found to increase with the increase in flow rate. Heating the charcoal to ∼ 100 °C resulted in degassing of the adsorbed (222)Rn, and the K of the degassed charcoal and virgin charcoal were found to be similar with no deterioration in performance indicating the re-usability of the charcoal.
authors: Centre for Advanced Research in Environmental Radioactivity, Mangalore University, Mangalagangothri - 574199, Mangalore, India. Electronic address: karunakara_n@yahoo.com.
authors: N
authors: N
authors: Karunakara
authors: Centre for Advanced Research in Environmental Radioactivity, Mangalore University, Mangalagangothri - 574199, Mangalore, India.
authors: K
authors: K
authors: Sudeep Kumara
authors: Centre for Advanced Research in Environmental Radioactivity, Mangalore University, Mangalagangothri - 574199, Mangalore, India.
authors: I
authors: I
authors: Yashodhara
authors: Radiological Physics & Advisory Division, BARC, Mumbai - 400085, India.
authors: B K
authors: BK
authors: Sahoo
authors: Radiological Physics & Advisory Division, BARC, Mumbai - 400085, India.
authors: J J
authors: JJ
authors: Gaware
authors: Radiological Physics & Advisory Division, BARC, Mumbai - 400085, India.
authors: B K
authors: BK
authors: Sapra
authors: Department of Chemical Engineering, Indian Institute of Technology Bombay, Mumbai - 400076, India.
authors: Y S
authors: YS
authors: Mayya
mesh_terms: D000327:Adsorption; D000396:Air Pollutants, Radioactive / Q000737:chemistry*; D016902:Air Pollution, Indoor / Q000517:prevention & control*; D000398:Air Pollution, Radioactive / Q000517:prevention & control*; D002606:Charcoal / Q000737:chemistry*; D003059:Cocos / Q000737:chemistry; D007194:India; D011886:Radon / Q000737:chemistry*
chemical_list: D000396:Air Pollutants, Radioactive; D002606:Charcoal; D011886:Radon
keywords: Activated charcoal; Adsorption; Adsorption coefficient (K); Breakthrough time (τ); Mitigation; Radon; Thoron