Leaching process investigation of secondary aluminium dross: investigation of AlN hydrolysis behaviour in NaCl solution

Abstract

The AlN hydrolysis behaviour in NaCl solution was investigated by immersing AlN powder in deionised water, 0·3 mol L⁻¹ NaCl aq and 0·6 mol L⁻¹ NaCl aq at 291 K respectively. The pH value of the suspension was monitored continuously for the first 4 days, and the amount of NH₃ formed within 10 days period was measured by water quality–determination of ammonium–distillation and titration method. The characterisation of the products after hydrolysis was carried out using X-ray diffraction, SEM and TEM analyses. It was shown that the hydrolysis process included a slow reaction period involving the dissolution of aluminium hydroxide layer around raw AlN particle, followed by the precipitation of aluminium hydroxide gel and the crystallisation of boehmite, bayerite and gibbsite. The effects of sodium chloride concentration on the hydrolysis behaviour are presented.