Abstract

Lokeshkumar P Ramteke, Raghav S Soni, Babulal Rebary, Ashwin W Patwardhan*, Dilip D Sarode and Pushpito K Ghosh*

Uranium concentrations were estimated of 11 phosphate fertilizer samples collected during 2016-2019 and also of 15 Di Ammonium Phosphate (DAP) samples procured from different regions of India during 2021-2022. The samples were analysed by Inductively Coupled Plasma Mass Spectrometry (ICP-MS), for which the quantification limit was 3 μg.L^-1. The reliability of the method was checked against laser fluorimetry and X-ray fluorescence analysis. The method was further validated through spiking studies. Uranium concentrations in the 2021-2022 sample collection were in the range of 8-360 mg [U].kg^-1 P₂O₅. The average uranium content was estimated to be 204.2 mg [U].kg^-1 P₂O₅, with standard deviation of 105.7 mg, which was comparable to the average of 243 mg [U].kg^-1 P₂O₅ reported for 303 phosphate fertilizer samples in a German repository. Following on from previous analyses of fluoride in phosphate fertilizers, the DAP samples collected during 2021-2022 were also analyzed for fluoride to assess the current scenario. Ion chromatography and ion selective electrode were employed for analyses, as before. Whereas a few samples contained negligible fluoride, the majority of the samples fell in the range of 20-40 g [F].kg^-1 P₂O₅, and one sample had as much as 53 g [F].kg^-1 P₂O₅. The average concentration was 24.3 g [F].kg^-1 P₂O₅, with standard deviation of 13.3 g. When compared with previous data, there was a worsening trend of fluoride contamination. No correlation was seen between uranium and fluoride concentrations. The incremental loads of uranium and fluoride in farmlands from application of DAP fertilizers were estimated to be 1,320 and 154,830 metric tonnes per annum, respectively, based on the 2020-2021 (April-March) DAP consumption figure of 11.911 million metric tonnes. Uranium and fluoride contamination emanating from application of phosphate fertilizer is a cause of concern that requires prompt remedial measures. If the uranium can be separated out and purified, it can help generate 8.8 GW of nuclear power. This is more than the present generation of 6.9 GW of nuclear power. Similarly, recovery and recycle of fluoride in desired form can cater to the entire requirement of the fluorochemicals industry.