Recovery of REEs from leaching liquor of ion-adsorbed-type rare earths ores using ionic liquid based on cooking oil

Ionic liquid (IL) based on tetraheptylammonium cooking oil (TC) was used for the first time to recovery rare earth elements (REEs) from leaching liquor of ion-adsorbed-type rare earths ores. Firstly, extraction performances of tetraheptylammonium oleate (TO) and tetraheptylammonium linoleate (TL) type ILs were investigated. It was shown that these ILs had good extraction performances, such as short equilibrium time less than 1 min, good extraction capacity of 0.225 mol/L and high stripping efficiency of 99%. Additionally, REEs extraction occurred in the solutions with high acidity (pH = 0.24) because the cation (C7H15)(4)N+ of TO and TL, could form a strong amine salt with hydrogen ion to decrease acidity of the feed solution. Also, an ion association mechanism of REEs extraction was proposed by FT-IR spectra, H-1 NMR investigation and slope analysis method. Secondly, TC was synthesized in water bath by mixing tetraheptylammonium bromide with saponified peanut oil. Then, comparative study of commercial extractants showed that TC had the highest REEs recovery yield of 100% from the leaching liquor. The sustainability, biocompatibility and non-toxicity, as well as simple synthesis route and well extraction performances make these cooking oil based ILs promising for REEs recovery from the leaching liquor