Phosphate Sorption Speciation and Precipitation Mechanisms on Amorphous Aluminum Hydroxide
- Huazhong Agricultural Univ., Wuhan (China); Univ. of Wyoming, Laramie, WY (United States)
- Stony Brook Univ., NY (United States)
- Umeå Univ., Umeå (Sweden)
- Canadian Light Sources, Inc., Saskatoon, SK (Canada)
- Huazhong Agricultural Univ., Wuhan (China)
- Univ. of Wyoming, Laramie, WY (United States)
- Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS), X-ray Science Division
Aluminum (Al) oxides are important adsorbents for phosphate in soils and sediments, and significantly limit Phosphate (P) mobility and bioavailability, but the speciation of surface-adsorbed phosphate on Al oxides remains poorly understood. Here, phosphate sorption speciation on amorphous Al hydroxide (AAH) was determined under pH 3–8 and P concentration of 0.03 mM–15 mM using various spectroscopic approaches, and phosphate precipitation mechanisms were discussed as well. AAH exhibits an extremely high phosphate sorption capacity, increasing from 3.80 mmol/g at pH 7 to 4.63 mmol/g at pH 3. Regardless of reaction pH, with increasing P sorption loading, the sorption mechanism transits from bidentate binuclear (BB) surface complexation with dP-Al of 3.12 Å to surface precipitation of analogous amorphous AlPO4 (AAP), possibly with ternary complexes, such as (≡Al-O)2-PO2-Al, as intermediate products. Additionally, the percentage of precipitated phosphate occurring in AAP linearly and positively correlates with P sorption loading. Compared to phosphate reaction with ferrihydrite, phosphate adsorbs and precipitates more readily on AAH due to the higher solubility product (Ksp) of AAH. The formation of AAP particles involves AlIII release, which is promoted by phosphate adsorption, and its subsequent precipitation with phosphate at AAH surfaces or in the bulk solution.
- Research Organization:
- Argonne National Laboratory (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- National Natural Science Foundation of China (NSFC); National Science Foundation (NSF); Swedish Research Council (SRC); USDOE Office of Science (SC)
- Grant/Contract Number:
- AC02-06CH11357
- OSTI ID:
- 1530214
- Journal Information:
- Soil Systems, Journal Name: Soil Systems Journal Issue: 1 Vol. 3; ISSN 2571-8789
- Country of Publication:
- United States
- Language:
- English
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