Effect of Flotation Time and Collector Dosage on Estonian Phosphorite Beneficiation

Abstract

Phosphorus is an essential and non-substitutable element for the cellular processes of all living organisms. The main source of phosphorus in the biosphere is phosphate rock. With more than 700 Mt phosphate rock, Estonia holds the largest sedimentary phosphate rock deposits in the European Union. Estonian phosphate rock is particularly outstanding due to its remarkably low content of hazardous heavy metals such as Cadmium (<5 ppm) and trace elements of Uranium (<50 ppm). It is also a reliable source of valuable elements such as rear earth elements (REEs). The aim of this study was to investigate the distribution of the main minerals (apatite and quartz) between slimes, tailings, and concentrates that formed at the froth flotation of Estonian phosphate rock with the up-to-date level of know-how and techniques. Subsequently, the relationship between the obtained grades and recovery levels in concentrates was determined based on the collector dosage and flotation duration. It was observed that the fine fraction of the tailings contains 17.9–33.49 wt% P2O5 that can be added to the final product. Moreover, it was found that, with the lower dosage of the collector, the extended flotation time does not influence the phosphate grade and a high amount of quartz remains in the concentrates. It was also shown that, by raising the collector dosage and setting the flotation time, an adequate grade (>32 wt% P2O5) and recovery (up to 98%) can be gained. The results showed that Estonian phosphate rock can be beneficiated to produce a high-quality concentrate at high recovery levels by modifying the main flotation parameters depending on the properties of the ore.