Silicon dioxide nanoparticles are stable in aqueous solutions compared to other particles which can affect their behaviour, e.g. in sewage treatment plants. In addition, silicon dioxide nanoparticles can bind other (harmful) chemicals already present in the environment.

 

Due to their negative surface charge under natural conditions, silicon dioxide nanoparticles are very stable in aqueous solutions compared to other particles. That is also why, in contrast to many other synthetic nanoparticles (e.g. Titanium dioxide, fullerenes), silicon dioxide nanoparticles do not bind humic acids even though other constituents of the natural organic matter can absorb to the surface. It was also found that in sandy soils smaller silica particles are less mobile than larger ones [1-3,6,8].

 

Kläranlage © Mariusz Szczygie / fotolia.com

In wastewater treatment plants, it is assumed for the purification of nanoparticle-containing effluents that a high salt content of the water will result in rapid agglomeration. This will lead to sedimentation of the particles and consequent removal of these particles from the water. However, this assumption does not apply to silicon dioxide nanoparticles due to their stability even in the presence of salt. Therefore, for this type of particle (and potentially other particle types), the wastewater cleaning procedure should include an additional filtration step [4]. (see cross cutting article – nanomaterials in the wastewater treatment plant)

Silicon dioxide nanoparticles are able to bind aromatic hydrocarbons such as phenanthrene and naphthalene [5]. The binding strength is dependent on the solutions’ pH. Silicon dioxide nanoparticles can also bind dichlorophen leading to an acceleration of degradation of this chemical [7]. Accordingly, silicon dioxide nanoparticles may alter the availability of contaminants for environmental organisms.

 

Silicon dioxide nanoparticles have a low tendency for agglomeration and sedimentation in aqueous solutions. They can bind various chemicals. This may have an impact on the effects of these chemicals on animals and plants.

 

 

Literature arrow down

  1. Yang, K et al. (2009), Langmuir, 25(6): 3571-3576.
  2. Zhang, Y et al. (2009), Water Res, 43(17): 4249-4257.
  3. Considine, RF et al. (2005), Aust J Chem, 58(12): 837-844.
  4. Zhang, Y et al. (2008), Water Res, 42(8-9): 2204-2212.
  5. Fang, J et al. (2008), Langmuir, 24(19): 10929-10935.
  6. Xue, N et al. (2016), Environ Sci Pollut Res, 23:11835-11844.
  7. Escalada, JP et al. (2014), Water Res, 50:229-236.
  8. Wang, C et al. (2012), Environ Sci Technol, 46:7151-7158.

 

 

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