Heavy Metal Immobilization Through Phosphate and Thermal Treatment of Dredged Sediments
Disposal of dredged sediments is expensive and poses a major challenge for harbor dredging projects. Therefore beneficial reuse of these sediments as construction material is highly desirable assuming contaminants such as heavy metals are immobilized and organics are mineralized. In this research, the effect of the addition of 2.5% phosphate, followed by thermal treatment at 700 C, was investigated for metal contaminants in dredged sediments. Specifically, Zn speciation was evaluated, using X-ray absorption spectroscopy (XAS), by applying principal component analysis (PCA), target transformation (TT), and linear combination fit (LCF) to identify the main phases and their combination from an array of reference compounds. In dredged sediments, Zn was present as smithsonite (67%) and adsorbed to hydrous manganese oxides (18%) and hydrous iron oxides (15%). Phosphate addition resulted in precipitation of hopeite (22%), while calcination induced formation of spinels, gahnite (44%), and franklinite (34%). Although calcination was previously used to agglomerate phosphate phases by sintering, we found that it formed sparingly soluble Zn phases. Results from the U.S. EPA toxicity characteristic leaching procedure (TCLP) confirmed both phosphate addition and calcination reduced leachability of heavy metals with the combined treatment achieving up to an 89% reduction.
- Research Organization:
- Brookhaven National Lab. (BNL), Upton, NY (United States)
- Sponsoring Organization:
- Doe - Office Of Science
- DOE Contract Number:
- DE-AC02-98CH10886
- OSTI ID:
- 959786
- Report Number(s):
- BNL-82772-2009-JA; ESTHAG; TRN: US201016%%930
- Journal Information:
- Environmental Science and Technology, Vol. 42; ISSN 0013-936X
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
54 ENVIRONMENTAL SCIENCES
ABSORPTION SPECTROSCOPY
BUILDING MATERIALS
CALCINATION
CONSTRUCTION
CONTAMINATION
DREDGE SPOIL
HEAVY METALS
IRON OXIDES
LEACHING
MANGANESE OXIDES
PHOSPHATES
PRECIPITATION
SEDIMENTS
SINTERING
SPINELS
TOXICITY
TRANSFORMATIONS
US EPA
USES
ZINC