Recovery of aluminium from a hazardous waste by precipitation as boehmite

Abstract

Boehmite was synthesized by a low temperature hydrothermal procedure, via sol-gel, from an aluminium hazardous waste (AHW). The method consisted of a first stage of acid digestion to solubilize the metal content, and a second stage of gel precipitation in alkaline medium. Several experiments were performed to study the effect of concentration, time and pH not only on the recovery of aluminium but on the purity of boehmite. A nanocrystalline boehmite was obtained as unique phase at pH8. At pH9 boehmite is obtained along with norstrandite. The complete characterization of samples was carried out by XRD, MEB, and TG/DTA. The procedure allows the recovery of 90% of the soluble aluminium content in the waste.