Radionuclides, trace elements, and radium residence in phosphogypsum of Jordan

Abstract

Voluminous stockpiles of phosphogypsum (PG) generated during the wet process production of phosphoric acid are stored at many sites around the world and pose problems for their safe storage, disposal, or utilization. A major concern is the elevated concentration of long-lived (226)Ra (half-life = 1,600 years) inherited from the processed phosphate rock. Knowledge of the abundance and mode-of-occurrence of radium (Ra) in PG is critical for accurate prediction of Ra leachability and radon (Rn) emanation, and for prediction of radiation-exposure pathways to workers and to the public. The mean (±SD) of (226)Ra concentrations in ten samples of Jordan PG is 601 ± 98 Bq/kg, which falls near the midrange of values reported for PG samples collected worldwide. Jordan PG generally shows no analytically significant enrichment (<10%) of (226)Ra in the finer (<53 μm) grain size fraction. Phosphogypsum samples collected from two industrial sites with different sources of phosphate rock feedstock show consistent differences in concentration of (226)Ra and rare earth elements, and also consistent trends of enrichment in these elements with increasing age of PG. Water-insoluble residues from Jordan PG constitute <10% of PG mass but contain 30-65% of the (226)Ra. (226)Ra correlates closely with Ba in the water-insoluble residues. Uniformly tiny (<10 μm) grains of barite (barium sulfate) observed with scanning electron microscopy have crystal morphologies that indicate their formation during the wet process. Barite is a well-documented and efficient scavenger of Ra from solution and is also very insoluble in water and mineral acids. Radium-bearing barite in PG influences the environmental mobility of radium and the radiation-exposure pathways near PG stockpiles.

Chemical composition and minerals in pyrite ash of an abandoned sulphuric acid production plant

“…It is hoped that the results will serve as a reference for similar studies in other countries where sulphuric acid has been produced from pyrite (Kawatra et al, 2002;Pérez-López et al, 2009;Rico et al, 2008a and2008b;Zeilinski et al, 2010). Given the extent of production of roasted sulphides and the limited literature available on their potential impact on the environment, the information presented in this paper (especially with regard to nanoparticles) may be of value in designing remediation strategies for roasted pyrite ash storage systems distributed around the world (Gupta et al, 1996;Kawatra et al, 2002;Lin and Qvarfort, 1996;Pérez-López et al, 2009;Salomons, 1995;Zouboulis et al, 1993).…”

Trace Element Contaminants and Radioactivity from Phosphate Fertiliser

“…In 2008, worldwide production of PG was on the order of 180 million metric tons (S. Jasinski, US Geological Survey, written communication, 2008in Zielinski et al 2011. A proportion of the trace elements found in phosphate rock are retained in the gypsum and the rest are transferred to the phosphoric acid.…”

210Pb and 210Po in Geological and Related Anthropogenic Materials: Implications for Their Mineralogical Distribution in Base Metal Ores

“…For example, Al Attar et al [114] report barite-strontianite solid solution and hokutolite [(Ba,Pb)SO4] as the main mineral components of radionuclide-containing scales associated with oil production. Extensive solid solution between isostructural Ba-and Ra-sulphates (so called radiobarite, (Ba,Ra)SO4 [165][166][167][168][169][170][171][172][173][174] has been modelled, and a number of natural occurrences have been documented e.g., [175,176]. In a detailed mineralogical insight into radionuclide host phases, Landa and Bush [79] document intense alpha particle activity associated with the presence of 210 Pb within micron-scale inclusions of anglesite within laths of gypsum.…”