title: Investigation of some factors affecting on release of radon-222 from phosphogypsum waste associated with phosphate ore processing.
abstract: The aim of this study is oriented to investigate the influence of some physicochemical factors such as radium distribution, grain size, moisture content and chemical constituents on releases of radon-222 from the accumulated phosphogypsum (PG) waste. The emanation fraction, activity concentration in the pore and the surface exhalation rate of radon-222 in the bulk PG waste are 34.5 ± 0.3%, 238.6 ± 7.8 kBq m(-3) and 213 ± 6.9 mBq m(-2) s(-1), respectively. These values were varied and enhanced slightly in the fine grain sizes (F1 < 0.125 mm) by a factor of 1.05 folds compared to the bulk residue. It was also found that release of radon from residue PG waste was controlled positively by radium (Ra-226), calcium (CaSO4) and strontium (SrO). About 67% of radon release attributed to the grain size below 0.5 mm, while 33% due to the large grain size above 0.5 mm. The emanation fraction of Rn-222 is increased with moisture content and the maximum emanation is ∼43% of moisture of 3-8%. It reduced slowly with the continuous increase in moisture till 20%. Due to PG waste in situ can be enhancing the background to the surround workers and/or public. Therefore, the environmental negative impacts due to release of Rn-222 can be minimized by legislation to restrict its civil uses, or increasing its moisture to ∼10%, or by the particle size separation of the fine fraction containing the high levels of Ra-226 followed by a suitable chemical treatment or disposal; whereas the low release amount can be diluted and used in cement industry, roads or dam construction.
authors: Hot Laboratories and Waste Management Center (HLWMC), Atomic Energy Authority of Egypt, Post Code No. 13759 Abu Zaabal, Cairo, Egypt.
authors: M A
authors: MA
authors: Hilal
authors: Hot Laboratories and Waste Management Center (HLWMC), Atomic Energy Authority of Egypt, Post Code No. 13759 Abu Zaabal, Cairo, Egypt. Electronic address: em_afifi1968@yahoo.com.
authors: E M
authors: EM
authors: El Afifi
authors: Hot Laboratories and Waste Management Center (HLWMC), Atomic Energy Authority of Egypt, Post Code No. 13759 Abu Zaabal, Cairo, Egypt; Chemistry Department, College of Science, Aljouf University, Skaka, Saudi Arabia.
authors: A A
authors: AA
authors: Nayl
mesh_terms: D000396:Air Pollutants, Radioactive / Q000032:analysis*; D002133:Calcium Sulfate / Q000737:chemistry*; D008906:Mining; D010710:Phosphates / Q000737:chemistry*; D010758:Phosphorus / Q000737:chemistry*; D011834:Radiation Monitoring; D011886:Radon / Q000032:analysis*; D012989:Soil Pollutants / Q000737:chemistry*
chemical_list: D000396:Air Pollutants, Radioactive; D010710:Phosphates; D012989:Soil Pollutants; C077769:phosphogypsum; D010758:Phosphorus; D011886:Radon; D002133:Calcium Sulfate
keywords: Emanation; Exhalation; PG waste; Radium-226; Radon-222