Abstract
Abstract The flotation process currently considered for apatite concentration from the Santa Quiteria phosphate deposit (Brazil), involves bulk flotation of apatite and calcite with anionic collector at pH=10 followed by calcite flotation at pH=5.5, adjusted with H3PO4. Although this concept is efficient from the point of view of separation between apatite and calcite, the intensive use of inorganic acids causes ion accumulation in the process water, especially Ca2+ and PO4 2-, which leads to problems in the flotation stage as well as in the environment. CETEM has been studying a process for the separation of carbonate minerals and apatite that involves the use of carbonic gas injected into the bubble generation system of flotation machines instead of inorganic acids. The aim of this study was to evaluate the effect of Ca2+ ion concentration on the water during the calcite flotation stage of the Santa Quiteria phosphate ore, between 6 mg/L (standard test) and 670 mg/L (maximun concentration) on the flotation performance in terms of P2O5 grade and its loss and the CaO/P2O5 ratio (RCP). The results indicated a reduction in the selectivity on the flotation of calcite from apatite for Ca2+ concentrations from 6 mg/L to around 285 mg/L. Despite this, the results obtained in this study indicated that the process based on the application of CO2 for the separation of calcite and apatite may be a technical alternative that causes less impact in flotation performance for the phosphate concentration ores with carbonated gangue.
Highlights
The agribusiness sector is of significant importance for the Brazilian economy
It was float fraction, an increase in the P2O5 observed that the P2O5 grade in the sink grade was observed as a function of a calcium concentration increase and ratio CaO/P2O5 (RCP) decrease to 5.1 considering the Ca2+ concentration (670 mg/L) from values of 7.6 for the lowest ions Ca2+ concentration
These results indicated a reduction in the selectivity of calcite flotation for Ca2+ concentrations studied, as a tendency in the increase of apatite flotation was evidenced by the increase of the P2O5 grade in the float fraction and the decrease of RCP values
Summary
The agribusiness sector is of significant importance for the Brazilian economy. Between 2000 and 2015, fertilizer use in the country went up by 87%. The national production of fertilizers is historically lower and did not grow as much as the national demand. Dependence on imports has been increasing year after year and, in 2015, about 65% of the total fertilizer consumption was supplied by imports (Cruz et al, 2017). Phosphate rock is a nonrenewable resource, which is the only economically feasible source of phosphate fertilizers. In Brazil, 13 phosphate mines were responsible for the phosphate production in 2014. Most of the national production - 82% - is located in the states of Minas Gerais and Goiás
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