Aggregation kinetics and mechanisms of silver nanoparticles in simulated pollution water under UV light irradiation

This paper investigated the effect mechanism of complex components (fulvic acid [FA], sodium dodecylbenzene sulfonate [SDBS], and sodium nitrate [NaNO3]) on the aggregation kinetics of polyvinylpyrrolidone‐modified silver nanoparticles (PVP‐AgNPs) under UV irradiation. The results showed that FA and NaNO3 alone did not cause aggregation due to the high steric hindrance and/or electrostatic repulsive forces. In high concentration of SDBS solution (20–50 mM), the stability of PVP‐AgNPs was reduced by adsorbing SDBS on nanoparticle surface and replacing their PVP coatings. A mixed system of two pollutants had a synergistic effect on PVP‐AgNPs aggregation. In the mixed system of SDBS and FA, the interaction of SDBS and PVP‐AgNPs dominated the aggregation of PVP‐AgNPs. NaNO3 significantly improved the aggregation rate of PVP‐AgNPs in SDBS solution due to the charge neutralization effect of electrolyte. In 20 mg/L FA solution, the aggregation rate increased slightly with increasing NaNO3 concentration from 50 to 200 mM due to the charge neutralization effect, while the hydrodynamic diameters of PVP‐AgNPs increased linearly and rapidly to micrometer size because the spatial conformation of adsorbed FA became compact in high‐salinity solution. The calculation results of eDLVO theory were basically consistent with most of the experimental results. Practitioner points PVP‐AgNPs was uniformly dispersed in NaNO3 or FA solution under UV irradiation. PVP‐AgNPs formed aggregates in SDBS solutions under UV irradiation. A system with two mixed pollutants had a synergistic effect on promoting aggregation of PVP‐AgNPs. eDLVO theory could explain the aggregation results in different chemical conditions except in NaNO3 solution. Aggregation behaviour of silver nanoparticles in single and mixed pollutant system under UV light irradiation.