Nanoscale ZnO particles are receiving increasing attention due to their widely used for commercial products and potential hazardous effect. The stability of ZnO NPs in the environment is mainly affected by inorganic ions and their characteristics are relevant to their fate and toxicities. In this study, three kinds of ZnO NPs were used to investigate their aggregation under various electrolyte additions: one commercial powder (P1), one commercial suspension (Sus) and one in-lab synthesized powder (P2). The particle sizes in water ranged from 68 nm to 17 um (Sus < P2 <P1). The pHzpc values of P1, P2 and Sus were 8.0, 9.7 and 10.3, respectively. The size of P1 reduced to 244 nm after sonication. The other two NPs were stable in water. The particle size of ZnO NPs increased when the ionic concentrations increased. The stability of ZnO NPs depends on their zeta potential, ionic types and ionic strength. In general, divalent ions were easier to neutralize the surface charge of particles and thus enhance aggregation than monovalent one. From the aggregation kinetics in the presence of different ions, the attachment efficiency of ZnO aggregates were constructed. The critical coagulation concentration (CCC) values of Sus and P2 ZnONPs were much larger than that of P1 ZnO NPs. Based upon the Derjaguin-Landau-Verwey-Overbeek theory, the interaction energies of ZnO NPs in the presence of different electrolytes were also evaluated. Our results indicated that critical ionic type and concentration promote the aggregation of different ZnO NPs. More attention was needed for the highly stabilized NPs in water.

Effect of electrolytes on the aggregation of three kinds of ZnO nanoparticles in water

248th National Meeting (2014)

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