Formation of Aluminum Hydroxides as Influenced by Aluminum Salts and Bases

Publisher Website
Google Scholar
Abstract
The influence of different ions in the formation of Al(OH)3 polymorphs has been studied experimentally by promoting stoichiometric reactions between the aluminum salts (AlCl3, Al(NO3)3, Al2(SO4)3) and bases (NaOH, KOH, NH4OH). In all cases the polymorphs obtained were a mixture of gibbsite, bayerite and nordstrandite or pseudoboehmite with the exception of the reaction between KOH, or NH4OH and Al2(SO4)3 which produced amorphous gels. Ageing of these gels at ambient temperature and pressure for 180 days or at 60°C for 20 days resulted in crystalline structure. Specifically, pseudoboehmite was crystallized from the reaction between Al2(SO4)3 and NH4OH. Significantly, of all ions present in solution in the present experiment, only the sulphate ones were observed to have a marked influence in the precipitation of Al oxyhydroxides.