Influence of silver nanoparticles on settling of suspended sediments

Silver nanoparticles (AgNPs) are one of the main nano-contaminants and their entry into the environment may pose a threat to the aquatic ecosystems . Meanwhile, AgNPs have an important impact on geological processes . In this paper, we studied the influence of AgNPs on the sedimentation of suspended sediments . Results showed the settling rate of sediments increased from 13.06 to 20.08 h −1 in the presence of 0.2 mg/L AgNPs. The morphology characterization indicated the average particle size of sediments increased from 34.74 to 42.87 μm after interacting with AgNPs, resulting in the acceleration of settlement on the basis of Stokes' law. The chemical analysis detected 43–57% of AgNPs were incorporated onto sediments, which was the dominant reason for the increased sediments size and settling rate. The influences of various water quality parameters, e.g., pH, ionic strength , temperature, humic acid and surfactant , on the sediments settlement and interaction with AgNPs were comprehensively studied. Elevating the solution pH, ionic strength, temperature, contents of humic acid and anionic/nonionic surfactants would suppress the settling of suspended sediments , whereas cationic surfactant showed a promoting effect on sediments settlement. In addition, the settling experiments were conducted in collected lake water and seawater , and results showed the real water matrices hindered the sediments settlement and interaction with AgNPs.