Recovery of Titanium from Ilmenite HCl Leachate Using a Hydrophobic Deep Eutectic Solvent

Currently, it is difficult to obtain high-purity titanium from ilmenite to produce titanium dioxide (TiO2). More severely, it causes serious environmental pollution. In this paper, a new hydrophobic deep eutectic solvent (HDES), a combination of decanol (DEO) as a hydrogen bond donor (HBD) with N,N-diisooctylacetamide (DOA) as a hydrogen bond acceptor (HBA), for the environmentally friendly recovery of Ti(IV) from ilmenite HCl leachate is proposed. The prepared HDES had low water cross-contamination, low viscosity, and sufficient density difference of HDES–water. The formation mechanism of HDES had been thoroughly revealed. In the ilmenite HCl leachate, the extraction effect of HDES on all metal ions had been studied in detail. Finally, rutile TiO2 and Fe2O3 were successfully synthesized using the obtained solutions as raw materials. The extraction mechanism characterized by Fourier transform infrared and 1H NMR spectroscopy was consistent with that determined by density functional theory (DFT) calculations. The slope method was used to study the effects of HBD, HBA, H+, Cl–, and H2O on the extraction of metal ions by HDES. In addition, the complex structures of HDES formed in the HCl solution are given. This article may thus help improve the sustainable utilization of some related metal ions from the real ore.