Study on the adsorption mechanism of green and efficient flotation reagents in the reverse flotation separation of limonite and quartz

This study achieved efficient reverse flotation separation of limonite and quartz using a green and efficient flotation reagent, polyaspartic acid (PASP), in the dodecylamine (DDA) flotation system. The flotation test found that under the conditions of pH 6, DDA concentration of 75 mg/L, and PASP concentration of 5 mg/L, the most significant flotation difference of 86.02 % was achieved between limonite and quartz. The contact angle test showed that after the simultaneous action of DDA and PASP, the contact angle of limonite decreased by 26.93° compared to DDA alone, while the contact angle of quartz increased by 8.68°. Zeta potential and infrared spectroscopy analysis indicated that PASP strongly adsorbed on limonite surface, hindering the adsorption of DDA on limonite surface, and weakly adsorbing on quartz surface, slightly affecting the adsorption of DDA on the surface of quartz. XPS analysis showed that PASP had a strong adsorption effect on Fe sites on limonite, while its effect on Si sites on quartz surface was weak, indicating selective adsorption characteristics on limonite. Extended Derjaguin–Landau–Verwey–Overbeek (E–DLVO) theoretical calculations showed that the introduction of PASP transformed the total mutual attraction energy between limonite particles and bubbles in the DDA system into total mutual repulsion energy, while the total mutual attraction energy between quartz particles and bubbles remained basically unchanged, causing the sinking of limonite and the rising of quartz, which was beneficial for the reverse flotation separation of limonite and quartz.