Eco-friendly sophorolipid enabling the selective and efficient flotation separation of ilmenite from titanaugite

Abstract

Ilmenite and titanaugite share similar surface chemistry and their selective separation presents challenges as conventional fatty acid-based collectors have several drawbacks. In this work, bio-based sophorolipid was assessed as an eco-friendly collector for selectively separating ilmenite from titanaugite. The results indicated sophorolipid can realize a faster and more efficient recovery of ilmenite than sodium oleate. The ideal pH range for ilmenite flotation was found to be between 6 and 8, with a maximum recovery of ∼95 % achieved at a sophorolipid dosage of 1 × 10^-4 mol/L. The critical micelle concentration of sophorolipid (1.6 × 10^-4 mol/L) was approximately one order of magnitude lower than that of sodium oleate (1 × 10^-3 mol/L), indicating that sophorolipid required a lower concentration to achieve effective surface coverage and create a hydrophobic ilmenite surface. Additionally, atomic force microscope observations revealed much thicker hydrophobic ilmenite interface when using sophorolipid as the collector, compared to sodium oleate, thus supporting a better ilmenite floatability. X-ray photoelectron spectroscopy, zeta potential, Fourier transform infrared spectroscopy and Raman measurements revealed that the negatively charged sophorolipid species adsorbed onto ilmenite surface and altered its electrokinetic property. Both iron and titanium present on the ilmenite surface acted as bonding sites for sophorolipid chemical adsorption. Moreover, the standard free energy for sophorolipid adsorption was the lowest at pH = 6, leading to increased adsorption of sophorolipid species onto ilmenite surface.