Characterization of Hydroxy‐Aluminum Solutions

Abstract

Hydroxy‐Al solutions were prepared and characterized with sulfate precipitation, resin treatment, and rate of Al‐ferron color development. The results suggest that the soluble Al species can be grouped into at least four categories: (i) high OH‐Al polymers — these have a residual positive charge of 0.33 or less per Al atom and are rapidly precipitable by Na2SO4, giving rise to the formation of noncrystalline basic aluminum sulfate; (ii) medium OH‐Al polymers — these form crystalline basic aluminum sulfate of composition Al(OH)2.50(SO4)0.22 · xH2O slowly and enter resin slowly; (iii) low OH‐Al polymers — these are not precipitable with Na2SO4, and they enter resin rapidly; and (iv) monomeric ions — these enter resin rapidly and react with ferron rapidly.

Differentiation of hydroxyl-aluminum species at lower OH/Al ratios by combination of 27Al NMR and Ferron assay improved with kinetic resolution

“…Although covering the whole space of Al content, it can give only a rough classification without any actual species in each category. For the more accurate speciation of these Al species, pseudo-first-order reactions and nonlinear regression methods have also been utilized to distinguish the hydroxyl-Al b by Zelazny and other authors [12][13][14][15]. However, their focus of attention emphasized mostly on the distinguishing of inert fraction from Al 13 at higher OH/Al ratio and the identification by 27 Al NMR has never been completed.…”

Effect of aging condition on species transformation in polymeric Al salt coagulants

“…From the difference in Al speciation results between Ferron assay and 27 Al NMR spectroscopy, it can be inferred that some other polymers, besides Al 13 , also exist in hydroxyl Al solutions. These polymers are often classified as Al a or Al b in Ferron assay, but can not be detected with 27 Al NMR spectroscopy [18,21,24]. With the addition of strong base into Al solution, these polymers changed from oligomers to high polymers and also finally transformed into Al(OH) 3 in these samples.…”

“…Thus, solution pH and turbidity were often simultaneously discussed to help the understanding of Al speciation results obtained by some other methods [7,9,11]. Structures of precipitate were also analyzed with X-ray diffraction analysis to probe the transformation process of Al species from monomer or polymer to Al(OH) 3 [21]. Additionally, morphology of hydroxyl Al sample has also been used to analyze Al species in solution.…”

“…Additionally, morphology of hydroxyl Al sample has also been used to analyze Al species in solution. However, only morphology of some precipitates separated from hydroxyl Al solution were studied by SEM [9,21]. The difference in morphology of hydroxyl Al solutions aged at various conditions has not yet been investigated.…”

Al(III) speciation distribution and transformation in high concentration PACl solutions

“…It is accepted prevalently that the Al(II1) ions in partially neutralized solution exhibit strong hydrolysis reactions and various polynuclear or polymer species in metastable state can be formed (Tang, 1998;Wang and Tang, 2001; Wang e t d . , 2002; Bersillon et d., 1980;Parker and Rertsch, 1992;Hsu, 1988; Alan, 198 1 ; Bottero P I d., 1987, 1988Brosset, 1952; Rowsell and Nazar, 2000; Allouche et d . , 2000;…”