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Radium in Phosphogypsum Leachates
Author(s) -
Rutherford P. M.,
Dudas M. J.,
Arocena J. M.
Publication year - 1995
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq1995.00472425002400020014x
Subject(s) - phosphogypsum , phosphorite , radium , phosphoric acid , leachate , phosphate , extraction (chemistry) , gypsum , chemistry , distilled water , radionuclide , environmental chemistry , nuclear chemistry , radiochemistry , mineralogy , geology , raw material , chromatography , paleontology , physics , organic chemistry , quantum mechanics
Phosphogypsum (PG) is an acidic by‐product of the phosphate fertilizer industry, and is produced in large quantities by the wet phosphoric acid process. Most PG is sluiced out to repositories, forming large stockpiles. Phosphogypsum is composed mainly of gypsum (Ca‐SO 4 ·2H 2 O), but contains impurities of environmental concern such as F − , acids, trace elements, and naturally occurring radionuclides, which originate from the phosphate rock used in processing. Possible movement of these impurities into groundwater is an issue. 226 Radium is the major source of radioactivity in PG produced from sedimentary phosphate rock. Few studies have addressed the leachability of 226 Ra because solid solutions of Ra, Ba, and Sr are very insoluble. The objective of this study was to investigate the concentrations of 226 Ra, Ba, and Sr in leachate generated from PG produced from Togo phosphate rock. Phosphogypsum was extracted 30 times with deionized distilled (d.d.) H 2 O over 30 d. Extractable 226 Ra was maximal (0.55 Bq L −1 ) for Day 1 but remained relatively constant between Day 2 and Day 30. Minimum extractable 226 Ra (0.23 Bq L −1 ) occurred on the Day 30 extraction but still exceeded the current U.S. drinking water standard. Solid phase 226 Ra increased between Day 0 (850 Bq kg −1 ) and Day 30 (1120 Bq kg −1 ). The 226 Ra/Ba ratios in the solid phase and in the extractable liquid phase were nearly equal over the last half of the extraction period. If this relationship holds for other PGs, then solution 226 Ra activities can be estimated if solid‐phase 226 Ra/Ba ratios are known and Ba solution concentrations are known or estimated.