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Research Project: Developing Technologies that Enable Growth and Profitability in the Commercial Conversion of Sugarcane, Sweet Sorghum, and Energy Beets into Sugar, Advanced Biofuels, and Bioproducts

Location: Commodity Utilization Research

Title: Surface interactions between gold nanoparticles and biochar

item Uchimiya, Sophie
item PIGNATELLO, JOSEPH - Connecticut Agricultural Experiment Station
item WHITE, JASON - Connecticut Agricultural Experiment Station
item HU, SZU-LUNG - University Of Texas At Austin
item FERREIRA, PAULO - University Of Texas At Austin

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/5/2017
Publication Date: 7/10/2017
Citation: Uchimiya, M., Pignatello, J.J., White, J.C., Hu, S.-L., Ferreira, P.J. 2017. Surface interactions between gold nanoparticles and biochar. Scientific Reports. 7:5027.

Interpretive Summary: Man-made nanomaterials are entering agricultural farms as pesticides, fertilizers, and as sludge/manure amendments. Because fundamental water chemistry controls the movement, availability, and toxicology of nanomaterials, this study investigated the chemistry of gold nanomaterials in soil media. This study discovered the key role of surfactant used to stabilize nanomaterials on their behavior in soils. Therefore, the role of surfactants should be incorporated into the environmental decision making processes.

Technical Abstract: Engineered nanomaterials are directly applied to agricultural soils as a part of pesticide/fertilize formulations and sludge/manure amendments. Yet, no prior reports are available on the extent and reversibility of gold nanoparticles (nAu) retention by soil components including charcoal black carbon (biochar). Citrate-capped nAu are negatively charged, and are expected to be repelled by negatively charged biochar surfaces. Transmission electron microscopy (TEM) showed the absence of >50 nm macropores in biochars that ˜50 nm nAu could penetrate. Therefore, both charge neutralization and pore penetration mechanisms were ruled out. However, the retention of citrate-capped nAu on 300-700 °C pecan shell biochars occurred rapidly and irreversibly. Retention of nAu was (i) greater on biochars than sandy loam soil; (ii) greater at higher ionic strength and lower pH; and (iii) pyrolysis temperature-dependent: 500 < 700 << 300 °C. Collectively, carboxyl-enriched 300 °C biochar likely formed strong hydrogen bonds with the citrate layer of nAu, while the charge transfer between the conduction band of nAu and '* continuum of polyaromatic sheets is likely to dominate on 700 °C biochar. Surface area-normalized retention of nAu on biochars (1.8'109-1.3'1011 nAu particles/m2) was several orders of magnitude higher than on carbon nanotubes and other negatively charged environmental surfaces, indicating its importance in the environmental fate assessment.