Novel extraction strategies for the concentration of ferric chloride

The objective of this research was to develop a novel, energy-efficient processes for concentrating ferric chloride solutions. When applying liquid-liquid extraction, the high energy for water evaporation can be avoided. Here, we report a study on the use of liquid-liquid extraction for concentration of ferric chloride solutions. First, a range of commercially available solvents (e.g. ethers, phenols, amides, thiols, amines) was screened at room temperature and under atmospheric pressure for an initial FeCl₃ concentration of 20 wt%, using a solvent/feed (S/F) ratio of 0.25. Hereafter, the extraction with the most interesting solvents was analyzed in more detail, and finally the recovery of FeCl₃ from the solvents was studied. From the screening it was concluded that diethyl ether and diisopropyl ether were the most promising, thus those two solvents were selected for a more detailed study. The FeCl3-extraction was studied at equilibrium for 0.5 < S/F < 2.0, 0 < pH < 1, 5 wt% < FeCl_3,initiai < 30 wt%), and at 295.15 K and atmospheric pressure. A complete (100% extraction yield, initial concentration 5 wt%) FeCl₃ extraction was coupled to a recovery by combined ether evaporation and back extraction with water to yield a final salt concentration of 45 wt%. Based on this result, we conclude that extractive concentration of FeCl₃ with ethers is a promising technology.