Characterization of Hydroxy‐Aluminum Solutions

Abstract

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 Na 2 SO 4 , 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 (SO 4 ) 0.22 · xH 2 O slowly and enter resin slowly; (iii) low OH‐Al polymers — these are not precipitable with Na 2 SO 4 , and they enter resin rapidly; and (iv) monomeric ions — these enter resin rapidly and react with ferron rapidly.