Characterization of the aluminum hydroxide microcrystals formed in some alcohol–water solutions

The crystallization in water of non-crystalline Al(OH)3 to form somatoids of aluminum trihydroxide bayerite is altered into other aluminum hydroxides when certain water-soluble alcohols are added. The crystalline and non-crystalline phases formed under the different environments were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), X-ray elemental microanalysis by using EDS/TEM and scanning electron microscopy (SEM). Ethylene glycol leads to nordstrandite and fibrillar pseudoboehmite. Methanol produces gibbsite and fibrillar pseudoboehmite. Ethanol has different effects according to its concentration: 20% produces bayerite+nordstrandite+fibrillarpseudoboehmite, 50% yields gibbsite+bayerite+pseudoboehmite, but 94% yields only fibrillar pseudoboehmite. Glycerol leads only to fibrillar pseudoboehmite. Isopropyl alcohol produces bayerite and nordstrandite. The presence of pseudoboehmite in the several systems suggests that the monohydroxide acts as an intermediate in the crystallization of the aluminum trihydroxides during aging in those alcohol–water solutions.