Influence of aluminum–sodium silicate on olivine flotation with sodium oleate

Abstract

In this work, the performance of the novel depressant aluminum–sodium silicate (Al–Na2SiO3) was compared to that of Na2SiO3, and the flotation and adsorption on the olivine surface were investigated with single-mineral flotation tests, zeta potential measurements, microcalorimetry, Fourier-transform infrared (FTIR) spectroscopy, and thermodynamic analyses. From the mineral flotation test results, Al–Na2SiO3 was found to exhibit an improved depression capacity as compared to the samples in the absence of Al3+, and the depression properties of Al–Na2SiO3 were found to depend on the Al3+ concentration. Thus, when the Al3+ concentration was higher than or equal to 0.1 mM, a significant depression capacity for olivine could be realized. From the obtained zeta potentials, it was found that by introducing assistant Al(III) species, the zeta potential of olivine exhibited a more positive integral shift than that of pure olivine and NaOL + Na2SiO3. In addition, according to the species distribution of Al2(SO4)3 and Na2SiO3, Si(OH)4 could interact with Al(OH)2+, Al(OH)2+, and Al3+ ions to form some monomeric silicate species and/or a polysilicate–aluminum material to inhibit the floatability of olivine. Moreover, the results of microcalorimetric measurements revealed that the reaction heats of the utilized reagents could be in the order of Al3+ < Na2SiO3 < NaOL and Al–Na2SiO3 + NaOL < Na2SiO3 + NaOL, suggesting that the NaOL species exhibited the highest affinities to the olivine surface and Al–Na2SiO3 impeded the adsorption of NaOL on the olivine surface. Furthermore, the thermodynamic analyses revealed that in the pH range of 2–9, the standard Gibbs free energy of Al3+ reacting with NaOL was lower than those of Mg2+ and Fe2+ but similar when the pH was above 9. This indicates that NaOL is more likely to interact with the Al3+ species in the pH range of 2–9; however, above pH 9, there is no significant difference in adsorption with Mg2+ or Fe2+. Finally, the FTIR spectra revealed that the adsorption of Al–Na2SiO3 + NaOL on the olivine surface was weaker than that of the sample without assistant Al ions.