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Synthesized iron oxide nanoparticles have been proposed as an alternative to non-dispersed iron oxides for in situ environmental remediation. Their colloidal properties enable their injection into porous media, i.e. soils and aquifers, and offer a higher efficiency in removing contaminants. However, this dispersed state is also the cause of concerns over their environmental fate and toxicity, e.g., by increasing the exposure time to aquatic organisms in groundwater remediation activities. Therefore, the objective of in situ groundwater remediation is to establish local reactive barriers in the subsurface by injection by means of reactive colloids with a controllable mobility under in situ conditions and present as colloids as shortly as possible. In this work, we examined the toxicity of humic acid-coated colloidal goethite nanoparticles in Daphnia magna . The adaptation of the ecotoxicological standard tests for nanomaterials is intensely discussed to increase comparability and reliability of results. In the present study, the effect of different exposure conditions on goethite nanoparticles colloidal behaviour and acute Daphnia immobilization effects was investigated. For this purpose, iron concentration in the water column, aggregation state and acute effects were studied in: i) a standard test, ii) test design with exposure dispersions incubated for a week and iii) water accommodated fraction. Despite the different aggregation and settling of the particles found between the approaches tested, no differences in toxicity were observed. Coated nanoparticles were found clogging up the filtering apparatus, and/or adhered to the exoskeleton, hindering the swimming and molting, and causing the immobilization and death of the organisms at doses of ≥ 943 mg/L (EC50). The data suggests that the toxic potential of these nanoparticles is mainly related to the physical interaction with the daphnids. [ABSTRACT FROM AUTHOR]

One of the most important applications of nanostructured TiO 2 is the manufacture of self-cleaning textiles. It is believed that the self-cleaning properties originate from the photocatalysis of water by nanostructured TiO 2 , but the mechanisms acting on textiles, and particularly the phenomena occurring at the interface, are not fully understood yet. A comparative study is proposed here to investigate the photocatalytic activity and the efficiency of modified TiO 2 nanomaterials with the purpose to identify the most suitable analytical method to probe photocatalysis in self-cleaning textiles. The present study sets up reliable, robust, fast and low-cost tests and compares them using TiO 2 /SiO 2 nanocomposite systems with different SiO 2 contents. The photocatalytic activity and efficiency of these nanocomposites were benchmarked by three different experimental protocols: a recently developed electrochemical technique to determine hydroxyl radicals ( OH) and two well-known methods, namely trapping of OH radicals by salicylic acid and degradation of Rhodamine B dye due to photocatalytic actions. The results suggest that the photoactivity of TiO 2 incorporated in textiles is mainly related to a direct reactivity of the surface oxidizing carriers toward the organic target molecule. The salicylic acid and Rhodamine B test provide mutually consistent results drawing similar trends of the photocatalytic performance. The electrochemical method turns to be a valid alternative when photocatalytic reactivity is driven by OH radicals diffused in a liquid medium. For self-cleaning textile applications, the salicylic acid test provides a more reliable quantitative prediction of the photocatalytic activity, while the Rhodamine B test represents a robust qualitative indicator. [ABSTRACT FROM AUTHOR]