Release of deposited MnO2 nanoparticles from aqueous surfaces

摘要

Changes in solution chemistry and transport conditions can lead to the release of deposited MnO2 nanoparticles from a solid interface,allowing them to re-enter the aqueous environment.Understanding the release behavior of Mn02 nanoparticles from naturally occurring surfaces is critical for better prediction of the transport potential and environmental fate of Mn02 nanoparticles.In this study,the release of Mn02 nanoparticles was investigated using a quartz crystal microbalance with dissipation monitoring(QCM-D),and different environmental surface types,solution pH values and representative macromolecular organics were considered.Mn02 nanoparticles were first deposited on crystal sensors at elevated NaN03 concentrations before being rinsed with double-deionized water to induce their remobilization.The results reveal that the release rate of Mn02 depends on the surface type,in the decreasing order:SiO2>Fe304>Al2 O3,resulting from electrostatic interactions between the surface and particles.Moreover,differences in solution pH can lead to variance in the release behavior of Mn02 nanoparticles.The release rate from surfaces was significantly higher at pH 9.8 that at 4.5,indicating that alkaline conditions were more favorable for the mobilization of Mn02 in the aquatic environment.In the presence of macromolecular organics,bovine serum albumin(BSA)can inhibit the release of Mn02 from the surfaces due to attractive forces.In presence of humic acid(HA)and sodium alginate(SA),the Mn02 nanoparticles were more likely to be mobile,which may be associated with a large repulsive barrier imparted by steric effects.