Theses and Dissertation

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Browsing Theses and Dissertation by Author "Mdachi, Daniel"

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    Valorization Potential Of Minjingu Tailings For Re Covery Of Phosphate Fertilizer And Their Environmen Tal Impacts
    (NM-AIST, 2024-12) Mdachi, Daniel
    Sedimentary and igneous rocks are the two principal sources of phosphate that are extracted and processed into fertilizer. Phosphate is lost into the tailings during the beneficiation process. The extraction and processing of phosphate rock generate substantial waste, including overbur den or mining waste and phosphate tailings (PTs) from the beneficiation process. The extraction and processing of phosphate rock may release radionuclides and heavy metals into the environ ment, which are harmful to living organisms. In order to accomplish this study, first was to evaluate the amount of phosphate in the tailings for possible recovery of the phosphate fertilizer. Second was to determine the concentration of the selected heavy metals and radioactive ele ments in the tailings. Energy-dispersive X-ray fluorescence spectrometry (ED XRF) was used to quantify the concentrations of the chemical composition of tailings for phosphate fertilizer and heavy metals while radionuclide concentrations were determined using a High Pure Garmin Energy detector (HPGe). It was found that the phosphate content in PTs varied from 12.91% of P2O5 (Tailings Dump 2) to 19.61% of P2O5 (Tailings Dump 1). The heavy metal concentrations that were examined were as follows: Cu (12.9 – 27.3) mg.kg-1, Fe (7944.2 – 19052.2) mg.kg-1, Mn (410.9 – 474) mg.kg-1, Ni (1.9 – 13.2) mg.kg-1, Al (3597 – 13129.2) mg.kg-1, Zn (195.2 – 281.7) mg.kg-1, Pb (0.7 –4.5) mg.kg-1, and As (2.7 – 11.3) mg.kg-1. However, the concen tration of radionuclides 226Ra, 232Th, and 40K ranged from 311 to 7606 Bqkg-1, 207 to 654 Bqkg-1, and 131 to 762 Bqkg-1, respectively. This study revealed that Minjingu PTs contain an amount of phosphate that may be recovered for commercial applications. The concentration of heavy metals (Cu, Fe, Ni, As, and Pb) are below the World Health Organization (WHO) permissible levels except for Zn which were above the permissible limit. The concentrations of radionu clides were found to be higher compared to the recommended world value. From the results obtained in this study, further research is recommended at the Minjingu mines to identify the optimal beneficiation methods for the recovery of phosphate from tailings.