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Effect of water and wastewater treatment on the properties of engineered nanomaterials (ENMs) in the context of their fate, toxicity and interaction with other contaminants (H2020-MSCA-IF-2015, No. 699794))

 

Preliminery Results

The results showed that effect of treatment on physico-chemical properties of ENMs depended on method of treatment and material tested. In the case of graphene nanoplatelets (GFs) with various surface area, UV, H2O2 and UV/ H2O2 treatment, only slightly affected this parameter (Figure 1). However, in the case of functionalized graphene nanoplatelets increasing of the surface area after UV/ H2O2 treatment of hydrocarbon functionalized GFs were observed. All treatments affected polycarboxylate functionalized GFs increasing surface area significantly. In the case of different nanohybrids and metal functionalized carbon nanotubes significant increase of surface area was observed after UV, H2O2 and UV/ H2O2 treatment. Generally, UV and H2O2 treatment of ENMs decreased the carbon content in these materials and increased the other elements, which was confirmed by FTIR spectra. However there were some exceptions, where increase of C was observed (for example UV/ H2O2 treated polycarboxylate graphene nanoplatelets). No differences were observed in properties of ENMs after their treatment between distilled water and modelled wastewater.


Figure 1.  Isotherms of N2 adsorption on graphene nanoplatelets

Aim (b) (WP2).

Size of aggregates with a few exceptions, did not change depending on the treatment method and the type of particles. ENMs formed the aggregates in a size between 800 and 1200 nm. After treatment, where the exceptions were observed, usually treated ENMs formed smaller aggregates (~800 nm) compare to pristine ones (>1000 nm). For most of the tested ENMs the treatment did not affect their behaviour in environmental systems and ENMs usually settle down regardless of the treatment after 3-5 days. Any trend, which could lead to specific conclusions (relation to the properties, etc.) was not observed. Effect of the pH and natural organic matter (NOM) and different cations (Na+ and Mg2+) on aggregation ability was also evaluated in the context of treatment. Changing of these parameters affected the aggregation ability of pristine ENMs. However, no differences between pristine and treated ENMs were observed. 

In the mesocoms experiment two coated nanocarbons (CNT-Zn, CNT-Cu) and two nanohybrids (graphene nanoplatelets-Zn and graphene nanoplatelets-Cu) obtained and characterized during WP1 were added to the mesocosm facility. CMF is home to simulated wetland ecosystems, enabling a wide array of uniquely realistic investigations into the mechanisms that govern ENMs transport, transformation, ecological interactions and biouptake. CMF mimics an emergent freshwater wetland environment. After 12-month study period, the concentration of elements (Zn and Cu) in water, sediment, plants and insects was determined to assess the long-term bioaccumulation of elements from the transformed ENPs. No difference in the concentration of Zn and Cu between the control (no nanoparticles) and experiments with pristine ENMs was observed in particular elemental systems. The concentration of metals was in the quite low level (background) and do not cause any risk for environment. Comparison between different treatments and pristine ENMs also did not show any differences between ENMs.

To a large extent, the impact of individual treatments depended on the ENMs tested. In general ozonation decrease adsorption kinetics of TCS and decreased adsorption affinity to almost all investigated ENMs (Figure 2). The opposite trend was observed for H2O2, UV and H2O2/UV treatment, which increased adsorption affinity of TCS, DFC, CAF and NAP by nanohybrids and nanocoated carbon nanoparticles as well as graphene nanopeletes. No effect of treatment was observed for phenanthrene. We also investigated the adsorption of organic matter by ENMs. The results varied and largely determined by the type of ENMs and the method of treatment.

Figure 2.  Kinetics (a) and Isotherms (b) of triclosan on different nanoparticles

Research Methodology
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Research Methodology