April 29-May 4, 2018
The most widely industrial flotation process for the treatment of phosphate ores containing carbonate as gangue minerals, especially in China, Saudi Arabia, Morocco, use strong acids, such as H3PO4 and H2SO4 as apatite depressants, and the carbonate minerals (especially calcite and dolomite) are selectively floated with the use of fatty acids as collectors at pH between 5.5 - 6.0. The flotation process currently considered for apatite concentration for the Santa Quitéria ore (Brazil) was developed in the middle of the 1980´s at the Center for Development of Nuclear Technology and involves bulk flotation of apatite and calcite with anionic collector (fatty acid soap) at pH=10 followed by calcite flotation at pH=5.5, adjusted with H3PO4. Calcite is collected in the froth phase and apatite concentrate is the sink product. Although this concept is efficient from the point of view of separation between apatite and calcite, the intensive use of strong inorganic acids (>15 kg/t) causes accumulation of ions in the process water, in particular Ca2+ and PO42-, which leads to problems in the flotation stage and also environmental. Process water containing large amounts of calcium, magnesium, fluoride and phosphate (phosphorus) directly influences the performance of apatite flotation (recovery and grade). Guimarães and Peres (1999) evaluated the effect of ions (dosed in the conditioning stage) on the flotation of barite and apatite. In both cases, the recovery decreased significantly as the ion concentration increased. Based on these results, limited ion concentrations as 20 mg/L ions Ca2+ and 30 mg/L Mg2+ were proposed to ensure the quality of recirculating water without impairing the flotation process. Santos et al. (2010) presents results of the effect of the ions concentration Ca2+, Mg2+, F- and PO42- on apatite recovery. The recovery of apatite decreases expressively with the increase in the concentration of fluoride, calcium, magnesium and phosphate ions, reaching a maximum reduction of 85% in apatite recovery. According to Hanna and Somasundaran (1976), the collector reacts with the calcium present in the apatite and also the Ca2+addition consumes the available collector for the mineral, resulting in a significantly reduction in apatite recovery. Aquino (1985) carried out studies with the Santa Quitéria ore evaluating the effects of calcium and magnesium ions concentration on the apatite flotation. The results indicated that concentrations of 49 mg/L Ca2+ and 30 mg/L Mg2+, the recovery decreased from 94.2% to 53.3% for P2O5 and for CaCO3 from 89.6% to 37.5%. 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 strong inorganic acids. The aim of this work is to evaluate the effect of Ca2+ ion concentration on the water just in the calcite flotation stage of Santa Quiteria’s ore. For the tests carried out with addition of Ca2+ ions, the concentrations above 95 mg/L, a reduction in the selectivity of the process is observed, since a tendency in the increase of the apatite flotation is evidenced, noted by the increase of the content of P2O5 in the floated fraction. For tests carried out recirculating the process water, the accumulation of Ca2+ ions from 8 mg/L to 285 mg/L increases apatite content in the calcite concentrate around 30%. However, at concentrations above 285 mg/ L of Ca2+ ions, the P2O5 content in the sink fraction and the P2O5 losses are not significantly affected. The results obtained in this study indicate that the process based on the application of CO2 for the separation of calcite and apatite may be a technical alternative for the concentration ores with carbonated gangue that causes less impact in the process residual water, since there is no addition of strong acids as apatite depressant.
Aquino, JA 1985. Influência de alguns íons sobre a flotação de apatita do minério de Itataia. In: Encontro Nacional de Tratamento de Minérios, Natal. Proceedings XL Encontro Nacional de Tratamento de Minérios e Metalurgia Extrativa; 1985, Natal, Brasil (In Portuguese).
Hanna HS, Somasundaran P. Flotation: Gaudin Memorial Volume. Ed Fuerstenau MC, New York: American Institute of Mining, Metallurgical, and Petroleum Engineers 1976. Flotation of salt-type minerals, p.197-272.
Guimarães RC, Peres AEC. Interfering Ions in the Flotation of a Phosphate Ore in a Batch Column. Minerals Engineering 1999,757-768.
Santos MA, Santana RC, Capponi F, Ataide, CH, Barrozo MAS. Effect of ionic species on the performance of apatite flotation, Separation and Purification Technology 2010, v.76,15-20.
Amanda Soares, Suzanne Ferreira de Mello, and Rafael Teixeira Rodrigues, "Effect of calcium concentration on calcite flotation from apatite using carbonic gas" in "Beneficiation of Phosphates VIII", Dr. Patrick Zhang, Florida Industrial and Phosphate Research Institute, USA Professor Jan Miller, University of Utah, USA Professor Laurindo Leal Filho, Vale Institute of Technology (ITV), Brazil Marius Porteus, Foskor-Mining Division, South Africa Professor Neil Snyders, Stellenbosch University, South Africa Mr. Ewan Wingate, WorleyParsons Services Pty Ltd., Australia Prof. Guven Akdogan, Stellenbosch University, South Africa Eds, ECI Symposium Series, (2018). http://dc.engconfintl.org/phosphates_viii/27