The application of atomic absorption spectrophotometry (AAS) for determining the content of heavy metals in phosphogypsum

Faculty of Agriculture, Belgrade-Zemun (1,2,3)
Faculty of Technology, Zvornik, Republic of Srpska (4)


Phosphogypsum is formed as a by-product in the process of 'green' phosphoric acid production. This is done in the so called 'wet process' by the action of sulphuric acid on raw phosphate at low temperature (<100 °C). Despite the same molecular formula and marked similarity with natural gypsum, phosphogypsum contains more than 50 impurities, and this is directly connected with the type of phosphate used in the production cycle. The aim of this paper was to consider the possibility of using phosphogypsum for amelioration of solonetz soil, bearing in mind its content of heavy metals, which are rather toxic for human organism and which can be transferred from soil to various plants used in human nutrition. On the other hand, there are very few data in the literature about the determination of heavy metals in phosphogypsum. The content of heavy metals in phosphogypsum was determined by atomic absorption spectrophotometry because this method has broad application in ana­lytical practice due to its high sensitivity, selectivity and precision. The results of the investigation indicate the following average content of heavy metals (in ppm): Fe-785, Pb-45, Zn-45, Cd-7, Mn-8, Co-10, Ni-20 and Cu-17. For the investigation of the effect of phosphogypsum on solonetz soil the following points were taken into consideration: maximum recommended dose of phosphogypsum (7 t/ha) for the amelioration of solonetz soil and the weight of soil layer (from 0 to 20 cm) having an area of 1 ha. The results obtained indicate that the amounts of heavy metals that are introduced into the soil with 7 t/ha of phosphogypsum are in the range from 0.035 to 0.8% of their maximum permissible content for arable soils. This means that only long-term application of phosphogypsum would introduce significant amounts of these elements into the soil.

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