Characterization of phosphate sequestration by a lanthanum modified bentonite clay: a solid-state NMR, EXAFS, and PXRD study.
Environ Sci Technol
; 49(7): 4559-66, 2015 Apr 07.
Article
in En
| MEDLINE
| ID: mdl-25747941
ABSTRACT
Phosphate (Pi) sequestration by a lanthanum (La) exchanged clay mineral (La-Bentonite), which is extensively used in chemical lake restoration, was investigated on the molecular level using a combination of (31)P and (139)La solid state NMR spectroscopy (SSNMR), extended X-ray absorption spectroscopy (EXAFS), powder X-ray diffraction (PXRD) and sorption studies. (31)P SSNMR show that all Pi was immobilized as rhabdophane (LaPO4·n H2O, n ≤ 3), which was further supported by (139)La SSNMR and EXAFS. However, PXRD results were ambiguous with respect to rhabdophane and monazite (LaPO4). Adsorption studies showed that at dissolved organic carbon (DOC) concentration above ca. 250 µM the binding capacity was only 50% of the theoretical value or even less. No other La or Pi phases were detected by SSNMR and EXAFS indicating the effect of DOC is kinetic. Moreover, (31)P SSNMR showed that rhabdophane formed upon Pi sequestration is in close proximity to the clay matrix.
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Phosphates
/
Bentonite
/
Eutrophication
/
Environmental Restoration and Remediation
/
Aluminum Silicates
/
Lanthanum
Language:
En
Journal:
Environ Sci Technol
Year:
2015
Type:
Article
Affiliation country:
Denmark