Changes in Phosphorus Adsorption Associated with Aging of Aluminum Hydroxide Suspensions1
- J. T. Sims and
- B. G. Ellis2
Phosphorus adsorption by “pure” Al-OH suspensions was examined as a function of pH of Al-OH precipitation, length of incubation, and ionic strength. Changes in P adsorption were measured through use of Langmuir isotherms after 30, 180, and 365 d of incubation. Physical characterization of changes in the Al-OH suspensions was accomplished through x-ray diffraction and scanning electron microscopy. Aging of Al-OH suspensions reduced their capacity for P adsorption, and while Al-OH precipitated at pH 5.5 initially adsorbed more P than that precipitated at pH 7.0, the difference became insignificant within 90 d. Reducing the ionic strength of the Al-OH suspensions by dialysis produced gibbsite and caused a decrease in the P adsorption maxima (Langmuir b value), further evidence that the polymerization/crystallization process is an important control of Al-OH reactivity for P.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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