Study On The Runoff Scouring Release And Mechanism Of Engineered Nanoparticles Contained In Composite Materials

With the development of nanotechnology,the production and application of nanocomposites have been significantly increased due to the unique properties of the added engineered nanoparticles?ENPs?.With the usage and aging of nanocomposites,the ENPs are inevitably released to the environment and their environmental residues in water,soil and air is increasing.As a consequence,that may lead to the environmental risks.Therefore,it is necessary to study the release and environmental behavior of ENPs.In this study,the effects of four factors?i.e.,weathering durations,water p H,rainfall durations and intensity?were investigated on the release of SiO₂-ENPs,Ag-ENPs and TiO₂-ENPs from paints applied on panels.The static water immersion test shows the concentration of studied particles all increase with weathering durations.At low and high pH,SiO₂-ENPs and Ag-ENPs show a higher release,while the release of TiO₂-ENPs is relatively high at low pH.With increased rainfall durations,the concentration released decrease for Si,and opposite is observed for Ag,while no obvious correlation is noted for Ti.With different rainfall intensity,all particles released show an increase tendency.In total,the release of Ag-ENPs and TiO₂-ENPs are extremely low and within the level of ppb,while SiO₂-ENPs reach ppm.Additionally,microscopic results highlight that SiO₂-ENPs are mainly released in form of agglomerates,only a small fraction is below 0.1 ?m.In view of the relatively large release of SiO₂-ENPs compared to Ag-ENPs and TiO₂-ENPs,this paper researched the SiO₂-ENPs behaviors in the environment,subsequently.In order to provide a comprehensive investigation of the phenomena of interaction of SiO₂-ENPs and natural waters in the present work,we studied the aggregate size,surface charge and percentage of nano-scale particles under the presence of monovalent cations,divalent cations and these two combined with natural organic matter?NOM?.Results show that the aggregation of Si O₂-ENPs is enhanced with the increase of cation concentrations,and divalent cations?Ca2+?have stronger influence on SiO₂-ENPs aggregate than monovalent cations.NOM adsorbed to the particles could make their zeta potential more negative,hence stabilizing them by electrostatic repulsion.In addition,SiO₂-ENPs size in solutions with humic acid?HA?is larger than that with fulvic acid?FA?.Divalent cations partially neutralize the adsorbed organic matter,and aggregation is enhanced with Ca2+,suggesting the presence of specific Ca2+-NOM bridges.For nano-scale particles,results revele that the percentage of nano-scale SiO₂ in NOM solutions shows the higher value at high pH than low pH,while at electrolyte?CaCl2 or Na Cl?and mixed solutions the percentage follow the order of: pH 7>pH 9>pH 5.