Comparison of the influence of tannic acid and selected low-molecular-weight organic acids on precipitation products of aluminum

摘要: The crystallization and surface properties of hydrolytic reaction products Al precipitated in the presence 1.0 · 10−6M 10−4M tannic acid from systems at initial concentrations 1.1 10−3M OH/Al molar ratios 2.0 or 3.0 were examined. X-ray diffraction analyses show that structural distortion within precipitation increases with ratio to Al. non-crystalline poorly ordered Al, including pseudoboehmite, are formed shown by transmission electron micrographs be fine, shapeless hollow colloids which deformed aggregated. In contrast low molecular weight organic acids (p-hydroxybenzoic, aspartic, malic, citric acids), influence on reactivities cannot solely explained basis its chemical affinity towards addition complexation, physical adsorption initially present apparently promotes thereby specific formation active sites for charge development phosphate Ca retention an extent even greater than observed more strongly complexing malic acid. On other hand, when concentration is increased 10−4M, acid, while enhancing through ability ionize provide negative charges, hampers masking some sites.