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

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 Al-2(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.