Nanoparticles Down the Drain Then What?

Transcription

1 Nanoparticles Down the Drain Then What? Kirk G. Scheckel E. Lombi, E. Donner, K. Vasilev, B. Miller, C. Impellitteri, T. Luxton Office of Research and Development National Risk Management Research Laboratory, Land Remediation and Pollution Control Division, Waste Management Branch

2 What are Nanoparticles? Engineered materials One dimension less than 100 nm Exhibits physical, chemical and biological properties that are particle size dependent Increase in surface areas increases reactivity and enhances intrinsic toxicity CdSe Nanoparticles Diameter of the particle (nm) 1

3 2 Nanoparticles are in Consumer Products

4 Nanoparticles are in Consumer Products 3 Silver speciation and release in commercial antimicrobial textiles as influenced by washing. E. Lombi, E. Donner, K.G. Scheckel, R. Sekine, C. Lorenz, N. Von Goetz and B. Nowack Chemosphere. 111:

5 Beneficial reuse of waste materials: Safely reducing or eliminating waste streams is a global priority o Preserve limited landfill space o Reduce demand of virgin materials o Conserve energy and GHG o Materials re-purposed for other uses Biosolids and biosolids-based products (compost) in the US results in nearly 7 million dry tons of material annually from about 16,500 MWTF ~55% of biosolids are land applied; remainder is incinerated/processed for energy recovery, composted or landfilled. 4

6 Nanoparticles are in Consumer Products and Biosolids HOME In reality, nanoparticles are added here 5 Not here

7 Scientific issues of adding nanoparticles at the end of the WWTP or directly to soil Historical research on metals in biosolids demonstrated a salt effect Metals spiked into soils Metals in WWTP biosolids Metals spiked into processed biosolids Metals in WWTP biosolids Why? ph and ionic strength changes Equilibrium perturbation Not the same reaction conditions Not the same reaction products Results are not comparable! 6

8 Experimental Design 60% primary sludge + 40% thickened WAS Bolivar WWTP, South Australia mg/kg Min Mean Max 95th 50th Silver Zinc 216 ND 8550 ND ND Targeted National Sewage Sludge Survey Treatments Ag 50mg/kg, Zn 400 mg/ kg Ø Zn and Ag salts Ø ZnO-NP (naked and trygiceride) Ø Ag-NPs (3 coatings) AgCl-NP Anaerobic digestion Ø 30 day digestion Ageing with wetting and drying cycles at 37 C for up to 6 months Sampling Ø 0, 3 hours Ø 1, 3, 10 and 30 days Fresh biosolids separated by centrifugation

9 Why simulating stockpiling/composting? Intensity B6 B5 B4 B3 B2 B1 Compost Aging Intensity Cubanite, CuFe 2 S 3 Covellite, CuS Chalcocite, Cu 2 S Cu-substituted goethite Cu-phosphate Cu-humic acid Energy (ev) Energy (ev) Cu is transformed from Cu(I)sulfide to Cu(II) sorbed by HA during composting/stockpiling (Donner et al., 2011; 2012) Cu-phosphate Cu-substituted goethite X(k) Cubanite, CuFe 2 S 3

10 Ag NPs in a model WWTP Normalised intensity AgCl bulk AgCl-NPs Metallic Ag Ag-NPs PVS Ag-NPs MSA Ag-NPs citrate Ag-acetate Ag-ferrih. Ag-cystine Ag-HA Ag 2 S Energy (ev) Transformation of Four Silver/Silver Chloride Nanoparticles during Anaerobic Treatment of Wastewater and Post-processing of Sewage Sludge. E. Lombi, E. Donner, S. Taheri, E. Tavakkoli, Å. Jamting, S. McClure, R. Naidu, B.W. Miller, K.G. Scheckel and K. Vasilev Environ. Pollut. 176:

11 Fate of Ag/AgCl-NPs during biosolid digestion: NPs disappearance is very rapid in all cases 0 h 30 d Ag-NPs PVS 2 m 6 m Composting Normalised intensity 0 h 30 d 2 m 6 m 0 h 30 d 2 m 6 m AgCl-NPs Composting Ag salt Composting High stability of secondary Ag 2 S-NPs Energy (ev) Kim et al., 2010

12 Ag NPs in fresh, aged and incinerated biosolids Ag NPs and AgNO 3 via influent of a pilot-scale wastewater treatment system consisting of a primary clarifier (PC), aeration basin, and secondary clarifier (SC). Solids were collected as fresh (24hr from PC) and aged (1mon from SC). Fresh and aged materials were incinerated at 850 o C. 11 Transformation of Silver Nanoparticles in Fresh, Aged, and Incinerated Biosolids. C.A. Impellitteri, S. Harmon, R.G. Silva, B.W. Miller, K.G. Scheckel, T.P. Luxton, D. Schupp, and S. Panguluri Water Research. 47:

13 Ag NPs in incinerated biosolids Normalized µ (Ε) Ag2SO 4 -ref Ag2S-ref Ag-Foil-ref AgNP-ref AgNP-ash Ag2S-ash AgNO 3 -ash Energy (ev) Transformation of Silver Nanoparticles in Fresh, Aged, and Incinerated Biosolids. C.A. Impellitteri, S. Harmon, R.G. Silva, B.W. Miller, K.G. Scheckel, T.P. Luxton, D. Schupp, and S. Panguluri Water Research. 47:

14 Fate of ZnO-NPs during a model biosolid WWTP digestion: Different Zn species can be discriminated using XANES Normalised intensity Zn-sulfide Zn-cysteine Zn-phosphate Zn-substitute ferrihydrite Zn-citrate ZnO-NP1 (OECD standard) ZnO-NP2 (as NP1 but in triglyceride) ZnO-NP3 (Co-doped) Energy (ev) Lombi et al., 2012

15 Fate Fate of ZnO-NPs of ZnO-NPs during during biosolid biosolid digestion: digestion: NPs disappearance NPs disappearance a function is very of rapid formulation in all cases a Time 0 d b c e f Time 3h days Control Control Control Zn salt Zn salt Zn salt Normalised intensity ZnO-NP1 ZnO-NP2 ZnO-NP3 Normalised intensity ZnO-NP1 ZnO-NP1 ZnO-NP2 ZnO-NP2 ZnO-NP3 ZnO-NP Energy (ev) Energy (ev) Zn sulfides are the final products

16 Biosolids ZnO are not NPs used in a straight model WWTP away: effect of composting/stockpiling on Zn Wastewater Anaerobic digestion Sewage sludge 2 months simulated composting Zn Sulfide Zn-P Zn-FeOH Fate of Zinc Oxide Nanoparticles during Anaerobic Digestion of Wastewater and Post-treatment Processing of Sewage Sludge. E. Lombi, E. Donner, E. Tavakkoli, T. Turney, R. Naidu, B.W. Miller and K.G. Scheckel Environ. Sci. Technol. 46:

17 Summary Ag converts primarily to Ag sulfide during WWTP; present in PC, SC, and anaerobic digesters ZnO converts to ZnS and then to Zn-phosphate and adsorbed phases upon aging/composting Incineration of Ag containing biosolids converts Ag sulfide to metallic Ag and Ag sulfate The environmental risk assessment of NPs for the waste water-biosolids-agriculture pathway can rely on the abundant information already available concerning metals in biosolids. 16

18 Synchrotron needs of environmental scientists. Faster detectors with lower detection limits/broader energy ranges/higher resolution/minimal deadtime Not all issues are related to contamination Use of relevant concentrations in experiments Smaller, focused beams will aid in understanding the dynamics of biogeochemical reactions Soils and environmental media are heterogeneous Ability to explore biological samples (plants, animals, organisms) without damaging or causing artifacts Better computing/read-out No need to have fast detectors if computers cannot keep up Balance between time and data quality, avoid under-sampling All in one beamlines Key advantages to conduct µ-xrf, µ-xas, and µ-xrd in one sitting 17

19 What environmental scientists need to consider. Synchrotron time is precious, plan accordingly, communicate with beamline scientists to ensure success More environmental scientists are coming to synchrotrons; more competition write better, convincing proposals publish your results Get involved participate on proposal review panels Don t start your research project at the synchrotron Conduct bench studies and understand your experimental design/system 18

20 In some cases, a synchrotron may not be necessary! We should get synchrotron time to confirm it! 19