Propriedades morfológicas, estruturais e interfaciais de fosfatos primários e secundários

Abstract

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 PO43- groups 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.