Lifetime and dissolution kinetics of zinc oxide nanoparticles in aqueous media

Abstract

We have assessed the persistence and lifetime of ZnO nanoparticles (ZnO-NPs) by performing dissolution experiments in three different aqueous media. These experiments were performed at ZnO-NP concentration levels close to the solubility of zincite (∼8 μM or 650 μg l(-1) of ZnO)-a concentration that is orders of magnitude higher than current estimated relevant environmental concentrations. The kinetics were followed by voltammetry, while maintaining the pH at about 7.5 using a CO2/N2 gas mixture to remove di-oxygen interference. Our results show that, under these conditions, ZnO-NPs readily dissolve with a lifetime expectancy that does not exceed 90 min. Water chemistry, especially the presence of dissolved organic matter (DOM), plays an important role in ZnO-NP dissolution. Dissolution rates significantly increase in the presence of strong chelating agents, EDTA and L-cysteine, while the addition of polymeric DOM, such as sodium alginate, has the opposite effect. Our results suggest that ZnO-NPs are unlikely to persist in natural aqueous media and that the toxicity should be primarily related to the released Zn(2+) ions rather than effects commonly associated to the presence of nanoparticles.

Dissolution kinetics of zinc oxide and its relationship with physicochemical characteristics

“…The first step prior to modeling is the selection of a physicochemical mechanism of dissolution that leads to the choice of the model [33,34,35,36]. Significant deviations from the exponential behavior has been observed for the dissolution of ZnO in environmental conditions [37]. Integration of Eq.…”

A Multi-Method Approach for Quantification of Surface Coatings on Commercial Zinc Oxide Nanomaterials

“…Our previous studies using NMR for quantification of functional groups on silica were based on the dissolution of the silica matrix in basic D 2 O (NaOD 0.4 M) which released the functional groups for solution NMR analysis and quantification by comparison to an internal standard. Since ZnO is insoluble in basic solution [26] we tested a comparable approach based on dissolving APTES-functionalized zinc oxide in acidic D 2 O (DCl 0.4 M). This did not always lead to the full dissolution of the powder; for example NAM-03-NH 2 produced a cloudy sample from which solids could be recovered by centrifugation (Table S1).…”

Unexpected insights into antibacterial activity of zinc oxide nanoparticles against methicillin resistantStaphylococcus aureus(MRSA)

“…Given the low solubility of ZnO, the concentration of free Zn 2+ ions is expected to be low in aqueous suspensions. However in the growth media, ZnO dissolution is complicated by Zn speciation with various components – amino acids and peptides – in the media 32, 35, 36 . Since most growth media is undefined soy digest products, it is difficult to predict ZnO dissolution kinetics and resulting complexes.…”