Improvement of determination method of calcium oxidein Phosphate Rock and Phosphate Fertilizer
Received:May 12, 2020  Revised:May 15, 2020
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DOI:10.3969/j.issn.2095-1035.2021.01.006
KeyWord:phosphate rock;phosphate fertilizer;EDTA;calcium oxide;method improvement
     
AuthorInstitution
QIlin luo 湖北冶金地质研究所中南冶金地质研究所
NI Haiyan 湖北冶金地质研究所中南冶金地质研究所
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Abstract:
      In order to solve the incomplete dissolution of calcium oxide in phosphate rock and phosphate fertilizer and eliminate the interference of phosphate, magnesium and iron in the determination process. The determination method of calcium oxide in phosphate rock and phosphate fertilizer was improved in this paper. Condition experiments such as selection of different acid dissolution systems, acid dosage, heating time, interference masking experiment, and pH value were carried out. The experiment determined that 10 mL of aqua regia and 3 mL of hydrofluoric acid were used for decomposition. The 2 mL of hydrochloric acid was added to dissolve salts. The 10 mL of dextrin and 5 mL of triethanolamine solution were added to mask the interference of Mg2+, Fe3+, PO43- and Al3+ . The extract does not need to be filtered. The EDTA was pre-added to clear solution at pH ≈ 7 and KOH was added to adjust solution pH > 13. Then added an appropriate amount of calcein indicator, and1titrated with EDTA until the green fluorescence disappears. Finally, calcium oxide in phosphate rock and phosphate fertilizer is obtained. The experimental results showed that the relative standard deviation (RSD,n=11) of calcium oxide in three phosphate rock standard samples and phosphate fertilizer monitoring samples were in the range of 0.21% ~ 1.11%. The measured value of calcium oxide in actual phosphate rock and phosphate fertilizer samples were consistent with that of the national standard method.
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