Aggregation and Dissolution of ZnO Nanoparticles in Solutions

Abstract

In the present study, aggregation and dissolution of 30 nm ZnO nanoparticles with concentration of 10 mg/L in different solutions were investigated. The solutions used were four types, three of among, which were double distilled water with the pH values adjusted to 5.5 (acid), 7.0 (neutral) and 8.5 (alkaline), respectively. The forth solution is modified Hoagland's solution. Changes of particle size of the ZnO nanoparticles in the solutions were determined and the concentrations of Zn²⁺ at 96 h were detected. The results show that aggregation occurred immediately after preparation and there were basically no ZnO nanoparticles in the supernatants after 12 h excerpt for the alkaline solution, suggesting pH value and ionic strength may influence the aggregation. Dissolution of the nanoparticles was highly pH-dependent. Acid facilitated and accelerated the process. Present results could provide supports for the ecotoxicological tests of the ZnO nanoparticles.