Stripping of Fe(III) from Aliquat 336 by NaH2PO4: implication for rare-earth elements recovery from red mud

A new approach was developed using NaH2PO4 as the stripping agent for Fe stripping from Fe-loaded Aliquat 336 during rare-earth elements recovery from red mud leachate. Owing to the strong coordination between Fe3+ and H2PO4‒, Fe mainly exists as FeH2PO42+ at [H2PO4‒] higher than 0.5 M, which can be readily stripped. The results showed a maximum Fe stripping efficiency of 95.5% under optimal condition. Moreover, the extraction capacity of the extractant after stripping was comparable to that of fresh extractant, and decreased only by 2% after 6 cycles, indicating the robustness of this approach for Fe stripping and extractant regeneration.