Coletores potencialmente seletivos na separação de apatita, calcita e dolomita

Abstract

The growing need for food and agricultural growth motivate the expansion of fertilizer production. In Brazil, the phosphate ores occur associated with silicates and carbonates. The chemical similarity between apatite, calcite and dolomite surfaces make their concentration by froth flotation extremely complex. This work aimed to identify potential zwiterionic collectors to improve the concentration of the phosphate ore named Catalão I. Initially microflotation tests were performed using apatite, calcite and dolomite with 10 different collectors in different concentrations: Hamposyl O (commercial grade oleoilsarcosine), Oleoilsarcosine (analitical grade), Hamposyl L (commercial grade lauroylsarcosine), Berol 867 (sarcosinate), Aero 830, Aero 845 and MC 711 (commercial grade sulphosuccinamates) as zwitterionic collectors; Flotigam EDA (amine) as cationic and Hidrocol (derived from vegetable oils) and oleic acid (analytical grade) as anionic ones. Zeta potential values were measured under the conditions which led to the highest selectivity. Microflotation tests using CO2 as a surface modifier were also carried out. The most selective conditions in the separation of apatite, calcite and dolomite were: (i) 50mg/L Flotigam EDA (amine) at 4<pH<8 and (ii) 20mg/L of oleic acid at 6<pH<10 where differences in floatability up to 80% were reached between apatite and gangue minerals without depressant. The zeta potential measurements indicated that Flotigam EDA (amine) adsorbing on apatite by electrostatic attraction and oleic acid probably by chemisorption. The other reagents have not indicated reasonable selectivity and zeta potential measurements confirmed the lack of affinity and/or low density of adsorption on the minerals. The microflotation tests using CO2(g) as a surface modifier have not increased the difference of flotability between apatite, calcite and dolomite with the reagents tested. However, the conditioning of mineral suspensions with CO2 caused changes in the aquatic chemistry of mineral suspensions, evidenced by the pH lowering of the suspension, especially in the case of calcite.