Ultrasonic Extraction of Trace Iron in Iron Tailings with Ionic Liquid [Emim]PF₆-Phenanthroline

Iron tailings are not only a waste of resource, but also bring serious environmental pollution. On account of the complex components and lower iron content in iron tailings, the ultrasonic extraction system of ionic liquid [Emim]PF₆-phenanthroline to extract trace iron from iron mud samples has been improved and the method is described in this paper. In order to improve the iron extraction rate from iron tailings, the effect factors were studied, such as the ionic liquid dosage, temperature and pH value on the extraction rate. The results show that the extraction rate of the trace iron from iron mud reached 92.74% under the addition of 0.8 mL phenanthroline, 1.0 mL ionic liquid, and the pH value was 7.3 when the extraction time was 30 minutes at 80℃. Moreover, the co-existence ions of K⁺, Na⁺, Ca²⁺, Mg²⁺ and Zn²⁺ had no effect on iron determination. Meanwhile, the back extraction study for the used ionic liquid revealed that the stability of the recovered ionic liquid was lowered when the pH value was more than 11. However, low temperature heating had relatively slight effects for back extraction on the used ionic liquid. The used ionic liquid can be treated and recovered with NaOH solution and the infrared spectrogram remained almost the same as the new ones, which can be reused after the recovery. Compared with the traditional methods of liquid-liquid extraction, this method has the advantages of lower dosage of ionic liquid, higher rate of extraction and easier recovery, and it can be applied to the recovery of the iron from iron tailings.