Process for Extracting Aluminum from Solutions.
U S Pat 3 545 920 1970 Dec; :
An alkyl phosphate, e.g., monododecyl phosphate, dissolved in kerosine is contacted with al-containing waste liquor maintained at ph 2.8-3.2, Whereby al is selectively extracted into the organic phase. The organic phase is then separated and the al stripped by contact with hcl. The resulting aqueous solution is then concentrated to crystallize alcl3.6H2o and the precipitate is filtered off and roasted to produce al2o3 as product and hcl for recycling. The extraction depends strongly on ph, reaching an optimum at ph approximately 3.1. If extraction is allowed to proceed unchecked, the ph of the aqueous phase drops and the extraction of al decreases or stops. To avoid this, finely ground limestone is added continuously to the extraction circuit at a rate sufficient to maintain the ph near 3.1. The method is suitable for recovering al from industrial and mine waste waters.
U.S. Pat. 3,545,920 Dec. 8, 1970, Chem. Abstr. 74:129,263V