On the fractionation of natural radioactivity in the production of phosphoric acid by the wet acid method

Raya, Juan Pedro Bolívar; Garcı́a-Tenorio, R.; García-León, M.

doi:10.1007/bf02164808

Cited by 61 publications

(35 citation statements)

References 5 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Previous studies have shown that most (90-100%) of the 226 Ra, 210 Pb (half-life = 22.6 years), and 210 Po (half-life = 138 days) in Florida phosphate rock reports to PG during the wet process, whereas the majority of uranium (U) partitions into phosphoric acid (Rutherford et al and references therein 1994;Hull and Burnett 1996;Bolivar et al 1996;Mazzilli et al 2000). Attempts to identify the mode of occurrence of 226 Ra in PG using size fractionation (May and Sweeney 1984;Beretka and Mathew 1985;Moisset 1990;Burnett et al 1995;Rutherford et al 1996) or selective sequential extraction (Burnett et al 1995(Burnett et al , 1999Santos et al 2006) have yielded inconsistent results.…”

Section: Introductionmentioning

confidence: 99%

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

Zielinski

Al-Hwaiti

Budahn

et al. 2010

Environ Geochem Health

View full text Add to dashboard Cite

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.

show abstract

Section: Introductionmentioning

confidence: 99%

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

Zielinski

Al-Hwaiti

Budahn

et al. 2010

Environ Geochem Health

View full text Add to dashboard Cite

show abstract

“…The 238 U decay-series may be uniformly distributed throughout the lattice structure of PG or can be bounded in separate, distinct mineral phases. Attempts have been made to identify the modes of occurrence of radionuclides in PG, in order to evaluate the availability of radionuclides ( 226 Ra, 210 Pb and 232 Th), rare-earth elements and Ba to the aquatic system under the influence of the stacks and its source materials based on sequential extraction methods (Tessier et al, 1979;Miller and Sutcliffe, 1984;Rutherford et al, 1995b;Boliver et al, 1996;Burnett et al, 1999;Santos et al, 2006). Their conclusion, however, cannot be confirmed clearly, since the phosphate rock and the chemical process vary for different industries.…”

Section: Introductionmentioning

confidence: 99%

Distribution and mode of occurrence of radionuclides in phosphogypsum derived from Aqaba and Eshidiya Fertilizer Industry, South Jordan

Al-Hwaiti

Zielinski²,

Bundham³

et al. 2010

Chin. J. Geochem.

View full text Add to dashboard Cite

Phosphogypsum (PG) is a by-product of the chemical reaction called the "wet process" whereby sulphuric acid reacts with phosphate rock (PR) to produce phosphoric acid, needed for fertilizer production. Through the wet process, some impurities naturally present in the PR become incorporated in PG, including U decay-series radionuclides, are the main important concern which could have an effect on the surrounding environment and prevent its safe utilization. In order to determine the distribution and bioavailability of radionuclides to the surrounding environment, we used a sequential leaching of PG samples from Aqaba and Eshidiya fertilizer industry. The results showed that the percentages of 226 Ra and 210 Pb in PG are over those in the corresponding phosphate rocks (PG/PR), where 85% of the 226 Ra and 85% of the 210 Pb fractionate to PG. The sequential extraction results exhibited that most of 226 Ra and 210 Pb are bound in the residual phase (non-CaSO 4 ) fraction ranging from 45%-65% and 55%-75%, respectively, whereas only 10%-15% and 10%-20% respectively of these radionuclides are distributed in the most labile fraction. The results obtained from this study showed that radionuclides are not incorporated with gypsum itself and may not form a threat to the surrounding environment.

show abstract

“…The high content of this rock in U-series radionuclides has already been well established [7]. This rock has also been used to study the mobility of U and other non-radioactive elements (Ba, Cd, Cu, Ni, Sr and Zn), which will allow us to evaluate how the phosphoric acid generation process in the production plant alters the mobility degree of the contaminants in the waste with respect to the original rock.…”

Section: Introductionmentioning

confidence: 99%

“…The radioactive impact originated by the radionuclides of the U-series contained in the phosphogypsums of Huelva is widely described in the literature [7,8]. The phosphogypsum stack, located in the tidal prism of the estuary (Fig.…”

Section: Introductionmentioning

confidence: 99%