Changes in Phosphorus Adsorption Associated with Aging of Aluminum Hydroxide Suspensions

• Published in: Soil Science Society of America journal Vol. 47; no. 5; pp. 912 - 916
• Main Authors: Sims, J. T., Ellis, B. G.
• Format: Journal Article
• Language: English
• Published: Madison, WI Soil Science Society of America 01-09-1983
• Subjects: Agronomy. Soil science and plant productions; Biological and medical sciences; Chemical, physicochemical, biochemical and biological properties; Fundamental and applied biological sciences. Psychology; Organic matter; Physics, chemistry, biochemistry and biology of agricultural and forest soils; Soil science; Adsorption; Phosphorus; Aluminium Hydroxides
• ISSN: 0361-5995; 1435-0661
• DOI: 10.2136/sssaj1983.03615995004700050014x

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.