Minério fosfático sílico-carbonatado: estudo fundamental

Abstract

The growth of the world population and the demand for food has increased the use of fertilizers. Despite the development of the Brazilian fertilizer industry and in the production of basic raw materials, including phosphate concentrate, the production is still not sufficient to meet the needs of the national consumption. From January to march 2007, Brazil imported 3.45 millions tons of fertilizers and 1.7 million metric tonsof raw materials. The beneficiation of ores with gangue containing silicates and carbonates is strictly necessary to enhance the recovery of this mineral resource. Nevertheless, the separation between phosphate and carbonates (calcite/dolomite),classified as sparingly soluble minerals, is difficult due mainly, to the similarities regarding this surface chemistry properties. As a consequence the flotation of the silicate-carbonate ores exhibits low selectivity in the presence of several collectors,including fatty acids, traditionally used in the direct flotation of phosphates. Among the ores types presents in the Alkaline-Carbonatitie Complexes of Catalão/GO and Araxá/MG, the silicate-carbonate ores present a strong potential, hindered by the difficulty in the processing due to the high content of carbonates in the gangue. The beneficiation of the silicate-carbonate ore would increased the throughput of the Catalãomine by 45% and of the Araxá mine by 50%. This investigation addressed the adsorption and co-adsorption of anionic and amphoteric collectors, corn starch and carboxymethylcellulose onto the surface of the minerals apatite, calcite, dolomite and vermiculite (from Catalão), via microflotation experiments and zeta potential determinations. The archived results suggested the possibility of the selective separation of apatite, by direct flotation at pH 9, with the use of the anionic collectors sodium oleate (Sigma-Aldrich Brasil Ltda) and MC711® (Cognis) and berol 867A®,MD20156® and MD20359® (Akzo Nobel) as amphoteric collectors. The adsorption of collectors onto the surface of the minerals under investigation is controlled by chemical mechanisms. For the collectors used (oleate, MC711, flotinor V3900-1® (Clariant),MD20156, MD20359 and berol) the carboxymethyl cellulose was at more efficient depressant for the system apatite/carbonate than starch. The most selectivecombinations of collector/depressant were MD20156/CMC, MD20359/CMC and flotinor/CMC.