TiO2 nanoparticles in aquatic environments: impact on heavy metals distribution in sediments and overlying water

The extensive application of TiO2 nanoparticles (NPs) highlights the importance of investigating their influence on aquatic systems. In this work, the effect of TiO2 NPs on heavy metals speciation was studied on a lab scale. For this goal, a series of aquaria containing water, sediment, and TiO2 NPs with various concentrations were set up. The study results revealed that TiO2 NPs caused (copper) Cu, (mercury) Hg, (titanium) Ti, and (zinc) Zn to be adsorbed by sediments in the forms of exchangeable and Fe-Mn species. According to measurements, 30 mu g/L of TiO2 NPs made Cu, Hg, Ti and Zn concentration in the water column decreased from 33, 1.14, 20, and 32 to 4, 0.58, 3, and 22.3 mu g/L, respectively. Manganese (Mn) was also adsorbed by sediment, and in all experiments, its concentration in the water column reduced from 44 to about 20 mu g/L. Due to the photocatalytic capacity of TiO2 NPs, arsenic (As) concentration in the water column increased from 0 to 8.7 mu g/L with the introduction of 30 mu g/L of TiO2 NPs. The sequential extraction results showed that in all experiments, concentrations of lead (Pb), nickel (Ni), and cobalt (Co) remained constant in different chemical species of sediment, which meant conservative behavior of them in presence of TiO2 NPs. In addition, a remarkable change was observed in water quality parameters such as ORP, TDS, TOC, BOD, NO3, and PO4 after the introduction of TiO2 NPs to aquaria. The reason behind these changes could be related to the decomposition of sediment organic content by TiO2 NPs.

Automated summary

This study investigated the influence of TiO2 nanoparticles on the speciation of heavy metals in aquatic systems. The results showed that TiO2 nanoparticles caused the adsorption of copper, mercury, titanium, and zinc by sediments in the forms of exchangeable and Fe-Mn species. Additionally, the introduction of TiO2 nanoparticles led to significant changes in water quality parameters.