Quantitative investigation of ZnO nanoparticle dissolution in the presence of δ-MnO2.

In this study, dissolution and transformation of ZnO NPs in the presence of δ-MnO2, an abundant and ubiquitous manganese (Mn) oxide mineral, was investigated via a suite of techniques covering bulk to molecular scales. Dissolution kinetics indicated that the presence of δ-MnO2 significantly affected ZnO NP dissolution rate/trend and equilibrium Zn2+ concentration, which were found to be mainly dependent on the concentration and mass ratio of ZnO NPs and δ-MnO2. Approximately 300 mg ZnO NPs per g δ-MnO2 was expected for ZnO NP uptake at pH 7.0 via ZnO NP dissolution and surface Zn2+ adsorption. X-ray diffraction (XRD), ζ potential, high-resolution transmission electron microscopy (HR-TEM), and Zn K-edge X-ray absorption spectroscopy (XAS) results revealed that when the mole content of ZnO NPs was less than the total adsorption sites of δ-MnO2 surface, ZnO NPs were completely dissolved and adsorbed on δ-MnO2 surface in the form of inner-sphere complexes. A fraction of ZnO NPs persisted when the mole ratio of ZnO to δ-MnO2 further increased. These results suggest that the transformation and fate of ZnO NPs is affected by environment-relevant minerals such as Mn oxides due to their huge capacity of fixing dissolved metal cations at the surface or interlayer structure. PMID: 32052339 [PubMed - as supplied by publisher]
Source: Environmental Science and Pollution Research International - Category: Environmental Health Authors: Tags: Environ Sci Pollut Res Int Source Type: research