Electrokinetic properties of wavellite and its floatability with cationic and anionic collectors

Abstract

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.

Electroflotation of precipitated phosphate from synthetic solution

“…In the pH range from 5 to 9, oleate ions (Ol-) and ion-molecule complexes H(Ol)-2 are the dominant species, whereas at pH >9 the dominant ions are Ol-and dimers Ol22-. Based on the distributions of the species mentioned above, in the pH range from 4 to 6, the increase in the negative zeta potential of the precipitate indicates the chemisorption of oleate ions and neutral molecules, oriented with head groups toward the solid, and with hydrocarbon chains toward the water solution, forming hemimicelles and rendering the surface hydrophobic, and therefore more floatable (Nunes et al, 2011;Vucinic et al, 2010). In the pH range from 7 to 9, the oleate ions and the ion molecule complex, oriented with head groups toward the solid and associated due to the chain-chain interaction into hemimicelles make the precipitate surface more hydrophobic and more floatable (Vucinic et al, 2010).…”

A mixed collector system for phosphate flotation

“…In weak alkaline solutions, ions and ion-molecule complexes of fatty acids both presented in the collector solutions. These species could adsorb at the apatite surface, which significantly improved the hydrophobicity of the apatite (Free and Miller, 1996;Lu et al, 1998;Nunes et al, 2011). However, at a pH above 10, the fatty acids dimers became the major species in which two fatty acids ions arranged in reverse (Vučinić et al, 2010).…”

Elimination of the Adverse Effect of Calcium Ion on the Flotation Separation of Magnesite from Dolomite

“…Additionally, these changes make it difficult to separate such minerals without additional treatment [31][32][33].…”