Efficient purification of Al by organic complexation method.

A method was developed for preparing high purity AlO(OH)(HO) (Al) through elimination of impurities by complexation. Polyaluminum chloride II (PAC) with Al content of 75% was adopted as the source of Al. The PAC was prepared under conditions of total aluminum concentration 0.1 mol/L and OH/Al ratio 2.2 to obtain the highest content of Al. A precipitation/metathesis method, organic solvent precipitation method and organic complexation method were examined to separate and purify Al. It was found that only by the organic complexation method could high purity Al products be obtained in large yield economically. In the experiments, benzoic acid was used as the coordinating reagent to decompose the main impurity AlOAl(OH)(HO) (Al), and the Al product could be obtained by precipitation and metathesis operations. It was noteworthy that the decomposition of impurities by benzoic acid could be completed in 2 hr. The Al product was characterized by Ferron assay, Al-NMR, SEM, XRD and TGA. The results showed that the purity of the Al product could exceed 92%.