Eco-toxicity of nanostructured ZnO, TiO2, Ce and Zr doped TiO2 developed for photocatalytic applications to Lemna minor and Sinapis alba

Introduction and scope of the work Eco-toxicological investigations of newly developed nanostructured materials for photocatalytic applications is a keen part of their development and introduction to practice. Highly... [ view full abstract ]

Introduction and scope of the work
Eco-toxicological investigations of newly developed nanostructured materials for photocatalytic applications is a keen part of their development and introduction to practice. Highly photoactive material suspected to be risky to human health and environment should not be introduced to practical life at all. In our study several nanostructured materials based on TiO2 (pure as well as newly doped by Ce and Zr) and ZnO were developed for the photocatalytic reduction of CO2 and the photocatalytic decomposition of N2O. Those photocatalysts investigated in our eco-toxicological study showed the highest photocatalytic activity for both mentioned reactions. Thus, logically their eco-toxicity to plant species such as Lemna minor fronds and Sinapis alba roots was examined.
Methods
The advantage of performed tests compared to often used acute aquatic toxicity tests according to the OECD 201 methodology using freshwater green algae (Desmodesmus subspicatus, Chlorella vulgaris) is the fact that the nanostructured materials do not have to be dissolved in water, thus the sedimentation of the nanostructured material is excluded, and the concentration series before testing do not have to be prepared. Another fact is the evaluation method. In the test on Desmodesmus subspicatus the results being determined by counting the algal cultures under the microscope, using an automatic cell counting, and this process is highly influenced by turbidity of the material. In the tests that were used in our study, meaning tests on Sinapis alba and Lemna minor, reading of growth inhibition was feasible not with standing any turbidity of the tested nanostructured materials.
Results
The acute biological toxicity of ten developed photocatalytically-active nanostructured materials was determined. A large number of them showed no toxic effect to Sinapis alba and Lemna minor. The acute biological toxicity of developed materials was correlated either with their microstructural and structural properties, or their chemical stability.
Acknowledgment
Financial support from the Grant Agency of the Czech Republic (project reg. No.14-23274S) is gratefully acknowledged. This work was also financially supported by EU structural funding Operational Programme Research and Development for Innovation (project No. CZ.1.05/2.1.00/19.0388).