The reverse apatite flotation with fatty acids has been widely used for the reduction of phosphorus content of magmatic origin iron ores. However, the occurrence of phosphorus intensely disseminated as secondary minerals such as wavellite renders the anionic reverse flotation a challenge. Zeta potential measurements and microflotation tests of wavellite with the use of anionic and cationic collectors were carried out in this work. The wavellite's IEP value was achieved at pH 4.5. Below the IEP value, the surface positively charged sites are made up of aluminum ions. The species H(+), Al(OH)(2)(+), Al(OH)(2+), Al(3+), OH(-), H(2)PO(4)(-), HPO(4)(2-), and PO(4)(3-) play a role in the protonation and deprotonation reactions that will determine the wavellite-solution interface properties. The highest values of wavellite's floatability under basic pH conditions were achieved in the presence of cationic collectors (1 × 10(-4) mol L(-1)). The formation of surface complexes and the precipitation of insoluble salt of aluminum onto wavellite surface seems to be the most likely hypothesis for the chemical nature interactions between amines and wavellite. The surface formation of aluminum oleate on the wavellite's surface seems to be the most probable hypothesis for the adsorption mechanism and the resultant high floatability of wavellite between pH 7.5 and pH 10.0 in the presence of sodium oleate (1 × 10(-4) mol L(-1)). The results showed that the cationic reverse flotation of secondary phosphates is a promising route to reduce the phosphorus content of iron ores from deposits that underwent a supergene enrichment process, since wavellite floatability in the alkaline pH range, using amine as collector, was not significantly affected by the presence of corn starch.
Because they are sparingly solubleminerals, the non-stoichiometric dissolution in aqueous media is one of the mainly mechanisms of surface charge generation in phosphates.The chemical composition and crystal structure will determine the interfacial properties of the phosphates, thus causing this mineral class to present major differences regarding interfacial properties and consequently, in flotation results. Apatite, wavellite, turquoise, and senegalite samples were characterized by X-ray diffractometry (XRD), X-ray fluorescence spectroscopy (XRF), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). Additionally, zeta potential measurements were performed as a function of the pH and time. The turquoise presented a amorphization tendency, which was exhibited in the XRD analysis. In the infrared spectroscopy, the main vibration bands related to PO4 3groups were observed in regions between 900-1100 cm-1. The displacement of the OH group vibration band to 3525 cm-1 in the apatite spectrum confirms that the sample is composed mainly of fluorapatite. The wavellite, turquoise and senegalite presented, respectively, weight losses of 24.92%, 18.73% and 18.55%, due to the presence of water molecules and hydroxyl groups in the crystal structures. The electrokinetic properties of wavellite, turquoise, and senegalite are mainly determinedby their cationic species and phosphate ions.
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