Effect of Phosphate, Sulfate, Arsenate, and Pyrite on Surface Transformations and Chemical Retention of Gold Nanoparticles (Au-NPs) in Partially Saturated Soil Columns

Environ Sci Technol. 2019 Nov 19;53(22):13071-13080. doi: 10.1021/acs.est.9b03241. Epub 2019 Oct 29.

Abstract

The understanding of engineered nanoparticle (ENP) fate and transport in soil-water environments is important for the evaluation of potential risks of ENPs to the ecosystem and human health. The effects of pyrite grains and three types of oxyanions-sulfate, phosphate, and arsenate-on the retention of citrate-coated gold nanoparticles (citrate-Au-NPs) were studied in partially saturated soil column experiments. The mobility of Au-NP was found to be in the order: Au-NP-sulfide (originating from pyrite) > Au-NP-sulfate > citrate-Au-NP > Au-NP-arsenate > Au-NP-phosphate. Chemical retention mechanisms, including hydrogen bonding and calcium bridging, are proposed and discussed. The retention of Au-NPs in soil columns increases with the increased ability of transformed Au-NP surfaces to create strong hydrogen bonding through adsorbed oxyanions with soil surfaces. Oxyanions were also found to reduce aggregation and aggregate size of Au-NPs upon interaction with Ca2+ solution. While the effects of cationic substances on ENP transport and stability have been studied frequently, the results here demonstrate that anionic substances have a substantial effect on Au-NP transport and stability. Furthermore, this study highlights the importance of examining ENPs under environmentally relevant condition, and the significant effect of ENP transformations on their mobility in soils.

MeSH terms

  • Arsenates
  • Ecosystem
  • Gold
  • Humans
  • Iron
  • Metal Nanoparticles*
  • Nanoparticles*
  • Phosphates
  • Soil
  • Sulfates
  • Sulfides

Substances

  • Arsenates
  • Phosphates
  • Soil
  • Sulfates
  • Sulfides
  • pyrite
  • Gold
  • Iron