Solid state NMR investigations of phosphate sequestration by modified clays and inorganic (oxy) hydroxides
EMSL Project ID
44623
Abstract
Phosphate, which is extensively used as a fertilizer and a detergent additive, is leached into fresh water bodies causing algae bloom and subsequent oxygen deficiency, especially in lakes. Two of the current restoration methods of phosphate polluted lakes are addition of aluminum chloride and a lanthanum modified clay (Phoslock). Phosphate is thereby immobilized by sorption on semi-amorphous aluminum hydroxides and as an insoluble lanthanum phosphate in a clay matrix, respectively. However, both methods have undesirable side-effects; the first method lowers the local pH values whereas the latter require large amounts of lanthanum, a limited resource. In addition, the long term fate of these precipitates is unknown. Thus, alternative methods with undesired side effects and which, ultimately, allow for regeneration of phosphate, itself a limited resource, are highly desirable. Our aim is to understand how phosphate is sequestered by these complex materials containing multiple phases and often of low crystallinity. We will use the high-field solid-state NMR (SSNMR) facilities at EMSL for detailed characterization of the magnesium and lanthanum containing phases and thereby gain insight into the phosphate sequestration process on the molecular level. Thus, 25Mg and 139La solid-state NMR spectroscopic studies of these complex, multiphase systems will be performed in order to understand how phosphate is bound and the long term stability of phosphate binding. The interpretation of our experimental results will be greatly enhanced by the use of molecular modeling using the strong computational chemistry facilities and scientific knowledge at PNNL. These high field solid-state NMR studies will be combined with phosphate sorption studies and a detailed characterization by 1H, 27Al, 29Si, and 31P SSNMR techniques and powder X-ray diffraction to gain insight into how the chemical structure determines the ion-sequestration properties.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2011-10-01
End Date
2014-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
Dithmer L, AS Lipton, K Reitzel, TE Warner, D Lundberg, and UG Nielsen. 2015. "Characterization of phosphate sequestration by a lanthanum modified bentonite clay: A solid- state NMR, EXAFS and PXRD study." Environmental Science & Technology 49(7):4559-4566. doi:10.1021/es506182s
Grube E, and UG Nielsen. 2014. "The Stoichiometry of Synthetic Alunite as a Function of Hydrothermal Aging Investigated by Solid-State NMR Spectroscopy, Powder X-ray Diffraction and Infrared Spectroscopy ." Physics and Chemistry of Minerals 42(5):337-345 . doi:10.1007/s00269-014-0724-7
Grube E., A.S. Lipton, and U. Nielsen. 2019. "Identification of hydrogen species in alunite-type minerals by multi-nuclear solid-state NMR spectroscopy." Physics and Chemistry of Minerals 46, no. 3:299-309. PNNL-SA-136099. doi:10.1007/s00269-018-1004-8
Petersen LB, AS Lipton, V Zorin, and UG Nielsen. "Local environment and composition of magnesium gallium layered double hydroxides determined from solid-state 1H and 71Ga NMR spectroscopy." Journal of Solid State Chemistry. doi:10.1016/j.jssc.2014.07.023
Pushparaj SSC, C Forano, V Prevot, AS Lipton, G Rees, JV Hanna, and UG Nielsen. 2015. "How the method of synthesis governs the local and global structure of zinc aluminum layered double hydroxides." Journal of Physical Chemistry C 119(49):27695-27707. doi:10.1021/acs.jpcc.5b09490