Influence of oxidation treatments on surface properties and reactivities of short-range ordered precipitation products of aluminum
1989
Violante, A. | Huang, P.M.
Organic C contents, specific surface and P adsorption of pseudoboehmites or x-ray noncrystalline precipitation products of Al formed in the presence of various organic ligands (citric, tartaric, tannic or aspartic acid) and Cl were studied before and after oxidation treatment of NaOCl or H2O2. Contents of residual C after NaOCl or H2O2 treatment ranged from 22 to 60% and from 55 to 90% of the original C, respectively. This evidence coupled with their IR spectra indicates that organic ligands are present on the surfaces and in the structural network of Al precipitation products. Specific surface values of samples formed in the presence of citrate or tannate were increased by NaOCl treatment, whereas those of samples formed in the presence of aspartate or Cl were relatively insensitive to oxidation. Before oxidation, samples formed in the presence of strong chelating ligands (citrate, tartrate, or tannate) adsorbed less P than those formed in the presence of aspartate or Cl. After oxidation, adsorption of P by samples formed in the presence of citrate and especially tannate was substantially increased. This is attributed to partial oxidation of organic ligands binding the precipitates and subsequent disintegration of aggregates. The data thus reveal that the influence of oxidation pretreatment on specific surface and P adsorption ability of Al precipitation products varied with the nature and amount of organic ligands coprecipitated.
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