DIVISION OF ENVIRONMENTAL CHEMISTRY

235th ACS National Meeting

New Orleans, LA

April 6-10, 2008

SUNDAY AFTERNOON

Environmental Behavior and Fate of Manufactured Nanomaterials

Fate and Transport

B. Xing, Organizer
J. A. Pedersen, Organizer, Presiding

1:30 — Introductory Remarks.

1:35 —26. Effects of small molecular weight acids on C60 aggregate formation and transport. P. J. Vikesland, X. Chang, L. K. Duncan, J. R. Jinschek, M. Chan

2:00 —27. Assessment of the fate of metal oxide nanomaterials in porous media. N. T. Loux, N. F. Savage

2:25 —28. Effect of nanoparticle aggregation, particle size distribution and concentration on transport of surface-modified nanoscale zero-valent iron (NZVI) particles in saturated porous media. T. Phenrat, F. Fagerlund, H -J. Kim, T. Illangasekare, R. D. Tilton, G. V. Lowry

2:50 —29. Effect of pH and clay on the transportability of surface-modified Fe0 nanoparticles in saturated sand columns. H -J. Kim, N. B. Saleh, T. Phenrat, R. D. Tilton, G. V. Lowry

3:15 —30. Behavior, fate and effects of different TiO2 nanoparticles in the aquatic environment. F. Kammer, S. Ottofuelling, S. Weilhartner, T. Battin, T. Hofmann

3:40 — Intermission.

3:55 —31. Fate and transport of ionic and nanoparticle silver released from commercially available socks. T. M. Benn, P. K. Westerhoff

4:20 —32. Analysis of Au nanorods in samples from an estuarine mesocosm study. T. J. Shaw, J. L. Ferry, C. R. Hexel, P. S. Craig, C. J. Murphy, S. Patrick, R. Frey, G. T. Chandler, A. Decho, P. Pennington, M. Fulton

4:45 —33. Transport of surface stabilized zero-valent iron nano particles in two-dimensional flow system packed with porous media. S. R. Kanel, R. R. Goswami, T. P. Clement, M. O. Barnett, D. Zhao

5:10 —34. Mobility of multi-walled carbon nanotubes in porous media. X. Liu, D. M. O’Carroll, E. Petersen, Q. Huang, L. Anderson

ABSTRACTS

ENVR 26

Effects of small molecular weight acids on C60 aggregate formation and transport

Peter J. Vikesland1, Xiaojun Chang1, Laura K. Duncan1, Joerg R. Jinschek2, and Matthew Chan1. (1) Department of Civil and Environmental Engineering, Virginia Polytechnic Institute and State University, 418 Durham Hall, Blacksburg, VA 24061, pvikes@vt.edu, (2) Institute for Critical Technology and Applied Science, Virginia Tech, Blacksburg, VA 24061

The discovery that negatively charged aggregates of C60 are stable in aqueous environments has elicited concerns regarding the potential environmental and health effects of these aggregates. Although many previous studies have used aggregates synthesized using intermediate organic solvents, this work employed an aggregate production method believed to more closely emulate the fate of fullerene upon accidental release – extended mixing in waters that contain small molecular weight acids (e.g., tartartic, citric and acetic acids). The aggregates formed in the presence of these acids tend to be more homogeneous in size than those mixed in water alone. In addition, the average diameter of the aggregates is smaller in the presence of low molecular weight acids than in their absence. The implications of these differences will be discussed in terms of both particle stability and transport through a sand-column.

ENVR 27

Assessment of the fate of metal oxide nanomaterials in porous media

Nicholas T. Loux, Ecosystems Research Division, U.S. Environmental Protection Agency, 960 College Station Road, Athens, GA 30605, Fax: 706-355-8104, loux.nick@epa.gov, and Nora F. Savage, ORD, NCER, U.S. EPA, Washington, DC 20460

This work assesses potential aqueous environmental metal oxide nanomaterial self-aggregation through the application of recent developments in surface complexation theory with historical DLVO procedures. Findings include: 1) nanomaterials with a Hamaker constant as large as 1E-19 J (and an absolute surface potential < 25 mV) will likely aggregate in most environmental aquatic media, 2) natural organic matter coatings may render metal oxide nanomaterials less likely to aggregate in aquatic media, 3) nanomaterials in aqueous suspension will likely have an absolute surface potential less than their micron-sized counterparts of the same composition and 4) robust diffuse layer model databases of intrinsic surface site reactivity constants with multi-valent aqueous environmental ions will need to be developed to provide accurate estimates of the surface potential of nanoparticles suspended in aqueous environmental systems.

Although this work was reviewed by EPA and approved for publication, it may not necessarily reflect official Agency policy.

ENVR 28

Effect of nanoparticle aggregation, particle size distribution and concentration on transport of surface-modified nanoscale zero-valent iron (NZVI) particles in saturated porous media

Tanapon Phenrat1, Fritjof Fagerlund2, Hye-Jin Kim1, Tissa Illangasekare3, Robert D. Tilton4, and Gregory V. Lowry1. (1) Department of Civil & Environmental Engineering, Carnegie Mellon University, 5000 Forbes Ave, Pittsburgh, PA 15213, tphenrat@andrew.cmu.edu, (2) Environmental Science & Engineering, Center for Experimental Study of Subsurface Environmental Processes at Colorado School of Mines, Golden, CO, (3) Center for Experimental Study of Subsurface Environmental Processes at Colorado School of Mines, Golden, CO, (4) Department of Chemical Engineering and Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213

Nanoscale zero-valent iron (NZVI) particles for in situ groundwater remediation are injected at high particle concentration (1-10 g/L) to minimize costs. At this particle concentration, aggregation and media ripening effects limit particle mobility. Understanding the deposition and transport of concentrated surface-modified NZVI dispersion is needed for efficient delivery and placement in the contaminant source zone. Here, the role of aggregation, particle polydispersity and particle concentration in the transport of poly(styrene sulfonate) (PSS)-modified NZVI in saturated sand columns is studied. Bench-scale column experiments are performed at various particle concentrations (0.03 to 6 g/L) in 10 mM Na+, a pore water velocity of 3.2 x 10-4 m/s, and with an average collector size of 300 µm. To elucidate the importance of particle polydispersity, transport and deposition of PSS-modified NZVI with three different particle size distributions are compared. The influence of magnetic attraction on their aggregation and deposition in porous media is assessed by comparing the deposition behavior of PSS-modified NZVI (magnetic) with PSS-modified hematite (nonmagnetic) with similar properties. The transport of PSS70K-modified hematite is not sensitive to particle concentration (from 30 mg/L to 6g/L) or particle polydispersity. In contrast, at high particle concentration (1 to 6 g/L), the transport of PSS70K-modified NZVI (magnetic particles) is sensitive to particle polydispersity, but insensitive to particle concentration. The different deposition behavior of the different NZVI size fractions is attributed to aggregation which is significantly different between three different size fractions because magnetic attractive forces increase with r6. Diaggregation and detachment from collectors due to fluid shear can explain the observed transport of PSS-modified NZVI at high concentration.

ENVR 29

Effect of pH and clay on the transportability of surface-modified Fe0 nanoparticles in saturated sand columns

Hye-Jin Kim1, Navid B. Saleh2, Tanapon Phenrat1, Robert D. Tilton3, and Gregory V. Lowry1. (1) Department of Civil & Environmental Engineering, Carnegie Mellon University, 5000 Forbes Ave. PH119, Pittsburgh, PA 15213-3890, hyejink@andrew.cmu.edu, (2) Department of Environmental Engineering, Yale University, New Haven, CT 06520-8286, (3) Department of Chemical Engineering and Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213

Surface modification of nano-scale zero-valent iron (NZVI) is necessary for its placement in groundwater DNAPL (dense non aqueous phase liquid) source zones. However, the transport of anionic polyelectrolyte-modified NZVI in sand columns can be affected by many factors including groundwater pH and the presence of clay particles. A fundamental understanding of how these factors affect NZVI mobility will aid in planning an injection or placement scheme for a desired NZVI distribution and treatment effectiveness. The effect of pH (5 to 8) and the presence of silica sand fines (2 to 15 wt %) and clay fines (2 to 15 wt %) on the mobility of modified nanoiron were evaluated in water-saturated sand columns. Modifiers included a high MW (125 kg/mol) tri-block co-polymer (PMAA-PMMA-PSS) and polyaspartate which is a low MW (2 to 3 kg/mol) biopolymer. Without excess polymer in solution, polyelectrolyte-modified NZVI was immobile in 15-cm sand columns at pH 6, but mobile at pH=8. The presence of 2 wt% kaolinite clay particles greatly reduced mobility at pH=8. Low transport of NZVI at low pH was caused by the aggregation of NZVI and higher attachment to the sand grains. The existence of silica fines did not inhibit the transport of NZVIs. On the other hand, clay fines limited the mobility of these particles significantly which is attributed to the pH dependent charge heterogeneity on clay mineral surfaces. A kaolinite-NZVI hetero-aggregation study and column transport studies with kaolinite and nano-iron over the pH range 5 to 8 confirmed the attachment of modified NZVI to kaolinite at pH<8. These results indicate that the hydrogeochemical conditions of an aquifer must be considered when selecting surface modifiers.

ENVR 30

Behavior, fate and effects of different TiO2 nanoparticles in the aquatic environment

Frank Kammer1, Stephanie Ottofuelling1, Stefan Weilhartner2, Tom Battin2, and Thilo Hofmann1. (1) Environmental Geosciences, Vienna University, Vienna 1090, Austria, Fax: 00431427753399, frank.kammer@univie.ac.at, (2) Freshwater Ecology, Vienna University, Vienna 1090

The special properties of engineered nanoparticles (ENP) may create a new industrial revolution; however, the same unique properties may appear undesirable as soon as they are active at the wrong place. The actual and future release of ENPs into the environment through various routes and in relevant amounts is directly connected to the success of current and future nanotechnology research. Hence the sustainable development of nanotechnology requires a profound risk assessment of the new products and this risk assessment requires a profound understanding of nanotechnology products' behavior in the environmental context. No need to emphasize that those new and unique properties may lead to new and unique reactions in the environment. On the other side, for many ENPs, the environmental behavior can at least be estimated from the knowledge accumulated in colloid chemistry.

One important pathway is expected to be via surface water transport. For surface water systems the homo- and hetero-aggregation of ENPs play a key role that determines the appearance and fate in the system. From this the main target organisms may be identified: free water column communities or sediment dwelling communities. Hence, the task is to test the aggregation behavior (colloidal stability) under environmental conditions, combine this with transport studies in surface waters and investigate effects on the target communities.

ENVR 31

Fate and transport of ionic and nanoparticle silver released from commercially available socks

Troy M. Benn, Department of Civil and Environmental Engineering, Arizona State University, Engineering Center G Wing, Room 252, Tempe, AZ 85287-5306, Troy.Benn@asu.edu, and Paul K. Westerhoff, Department of Civil and Environmental Engineering, Ira A. Fulton School of Engineering, Arizona State University, Tempe, AZ 85287-5306

Manufacturers of clothing (e.g., socks) employ nanosilver (n-Ag) as an antimicrobial agent to minimize odor-causing microbial growth, which may have adverse health affects on organisms when released into the environment. Six types of socks, allegedly containing n-Ag, were characterized and washed with water to assess the potential release of silver (ionic and colloidal) into domestic wastewaters. The silver contents of the socks were less than 1,360 µg-Ag/g-sock. The mass of leached silver in any wash (500 mL) ranged from 0 to 650 µg. Filtration and ion selective electrode (ISE) support a conclusion that silver is leached in colloidal and ionic forms. Based upon sorption tests, a model for a wastewater treatment plant (WWTP) suggests that an influent concentration of 2,900 ppb of this leached silver would produce an effluent exceeding the 1.9 ppb EPA salt water quality criteria level.

ENVR 32

Analysis of Au nanorods in samples from an estuarine mesocosm study

Timothy J. Shaw1, John L. Ferry1, Cole R. Hexel1, Preston S. Craig1, Catherine J. Murphy1, Sisco Patrick1, Rebecca Frey1, G. T. Chandler2, Alan Decho3, Paul Pennington4, and Michael Fulton5. (1) Department of Chemistry and Biochemistry, University of South Carolina, 631 Sumter Street, Columbia, SC 29208, shaw@mail.chem.sc.edu, (2) School of Public Health, University of South Carolina, Columbia, SC, (3) Department of Environmental Health Sciences, University of South Carolina, (4) Hollings Marine Laboratory, National Oceanographic and Atmospheric Administration, Charleston, SC, (5) NOAA National Ocean Service, Charleston, SC 29412-9110

The analysis of Au nanorods (60 nm x 15 nm; cetyltrimethylammonium bromide stabilized) in a series of samples collected for an estuarine mesocosms study is presented. Au nanorod suspensions were added to three identical mesocosms and samples of water, sediment, biofilms and tissue phases were collected to measure Au distributions over time. Initial gold particle loadings were nominally 3.6x1010 particles/L. The stability of Au nanorod suspensions in natural waters (fresh to saline) were investigated in a variety of sample containers to minimize sample loss to container walls. Methods of injection of aqueous samples containing Au nanorods into an ICP-MS were investigated. Direct injection of particles in aqueous samples was compared to pre-digestion of particles with aqua regia. Both methods were comparable within 5%. However, direct injection of particles resulted in memory effects in the spray chamber. Solid samples were digested using a modified HF-HNO3 digestion followed by uptake in aqua regia. Results from aqueous, sediment, biofilm and tissue phases will be presented.

ENVR 33

Transport of surface stabilized zero-valent iron nano particles in two-dimensional flow system packed with porous media

S. R. Kanel, R. R. Goswami, T. P. Clement, M. O. Barnett, and D. Zhao, Department of Civil Engineering, Auburn University, 238 Harbert Engineering Center, Auburn, AL 36849, srk0001@auburn.edu

Zero-valent iron nano particles (INP) were synthesized and stabilized with poly-acrylic acid to yield stabilized INP (S-INP). A two-dimensional physical model is developed and used to study the transport of these nano materials such as pristine INP and S-INP in a porous media under saturated conditions at fixed flow rates and initial concentration of nano materials. Transport data for INP, S-INP and a non-reactive tracer were collected under similar flow conditions. The results show that the transport of S-INP was the same as trace whereas bare INP did not show transport characteristics. Interestingly, it was observed that the S-INP plume migrated downwards as it transited horizontally in the physical model, indicating that the density of the suspension affected the transport of S-INP. The variable-density groundwater flow model SEAWAT was used to model the observed density-driven transport patterns. The data clearly show the importance of density effects, which cannot be fully discerned using one-dimensional column experimental setups. Finally, we have also shown that the numerical model SEAWAT can be used to predict the density-driven transport characteristics of S-INP in groundwater aquifers.

ENVR 34

Mobility of multi-walled carbon nanotubes in porous media

Xueying Liu1, Denis M. O’Carroll1, Elijah Petersen2, Qingguo Huang3, and Lindsay Anderson4. (1) Department of Civil & Environmental Engineering, The University of Western Ontario, London, ON N6A 5B9, Canada, docarroll@eng.uwo.ca, (2) Department of Civil and Environmental Engineering, University of Michigan, Ann Arbor, MI 48109-2125, (3) Department of Crop and Soil Sciences, University of Georgia, Griffin Campus, Griffin, GA 30223, (4) Biological and Environmental Engineering, Cornell University, Ithaca, NY

Engineered multi-walled carbon nanotubes (MWCNTs) are the subject of intense research and are expected to gain widespread usage in a broad variety of commercial products. However concerns have been raised regarding their potential environmental and health risks. The mobility of MWCNTs in porous media is examined in this study through one dimensional flow-through column experiments under conditions representative of subsurface and drinking water treatment systems. The goal of this work was to determine dominant MWCNT removal mechanisms and factors that control MWCNT transport. Results demonstrate that pore water velocity strongly influenced MWCNT transport, a result that stands in contrast to traditional colloid filtration theory, which suggests a relatively minor effect of flow velocity in comparison to Brownian diffusion. Experiments conducted at different ionic strengths indicate that both particle deposition and straining are important MWCNT removal mechanisms from the aqueous phase. Given these findings, traditional colloid filtration theory may not be appropriate for the prediction of MWCNT mobility in porous media. This may be due to the large aspect ratio of the MWCNTs and the importance of straining in MWCNT removal.