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Transformation of Silver Nanoparticles in Fresh, Aged, and Incinerated Biosolids
Citation:
Impellitteri, C., S. Harmon, G. Silva, B. Miller, K. Scheckel, T. Luxton, D. Schupp, AND S. Panguluri. Transformation of Silver Nanoparticles in Fresh, Aged, and Incinerated Biosolids. WATER RESEARCH. Elsevier Science Ltd, New York, NY, 47(12):3878-3886, (2013).
Impact/Purpose:
Results on the fate and tranport of silver nanoparticles in wastewater.
Description:
Abstract The purpose of this research was to assess the chemical transformation of silver nanoparticles (AgNPs) in aged, fresh, and incinerated biosolids in order to provide information for AgNP life cycle analyses. Silver nanoparticles were introduced to the influent of a pilot-scale wastewater (WW) treatment system consisting of a primary settling basin, aeration basin, and secondary settling basin. The partitioning of the AgNPs between the aqueous and solid phases in the system was monitored, and the majority of AgNPs were found in the solid phase of the primary settling basin. Less than 3% of the total AgNP introduced into the primary clarifier (PC) was measured at the overflow of the PC (i.e. 97% were trapped in the PC). Biosolids were collected from the pilot-scale system for silver analyses, including Ag concentration and speciation. Additionally, biosolids were collected from a publically owned treatment works (POTW). The POTW biosolids were spiked with AgNPs, AgNO3, and Ag2S and analyzed by acid digestion/inductively coupled argon plasma spectroscopy. One set of the spiked POTW biosolids was aged for one month, and another set was analyzed within 24 hours via X-ray absorption spectroscopy (XAS) and scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM-EDX) in order to determine Ag chemical speciation and elemental associations. Replicates of the aged and 24-hour samples were also incinerated at 850˚C for 4 hours. The residual ash was analyzed by XAS and SEM-EDX. The results show that AgNPs are converted to Ag2S species in fresh and aged biosolids, which is in agreement with other studies on AgNPs in biosolids. Results from linear combination fitting of the XAS data for incinerated biosolids show that a significant proportion of the AgNPs (30-50%) are converted back to elemental Ag in the incineration process. In addition to elemental Ag, the results suggest the presence of Ag2SO4 (26-30%), and Ag2S (21-32%) in the incinerated biosolids. Incinerated biosolids spiked with AgNO3 and Ag2S exhibited similar transformations. These transformations of AgNPs should be accounted for in life-cycle analyses of AgNPs and in management decisions regarding the disposal of incinerated biosolids.
