nanomateriály

Interactions of iron-based nanoparticles with river water and reservoir water were studied in this diploma thesis. NANOFER STAR, Carbo-Iron and ferrihydrite were selected as the representatives of the iron-based nanoparticles. NANOFER STAR is commercially produced for remediation of contaminated soils and ground waters and Carbo-Iron is studied as promising material for advanced application in remediation technologies and thus they would be purposely in contact with the natural environment. Ferrihydrite is a naturally occurring material, here served as a control inert nanoparticle. The study interest was in fate of these nanoparticles in environmentally relevant media. The main objectives were: i) to describe what happens when iron-based nanoparticles are released into aqueous environment; ii) to characterize the nanoparticles using different methods and analyses; iii) to assess potential toxicity of newly prepared and aged nanoparticle suspensions using model bacteria Escherichia coli. Real river water samples were obtained from St. Annes Park in Dublin (Irish Republic) and real reservoir water samples were obtained from Harcov reservoir in Liberec (Czech Republic). The nanoparticle suspensions were dispersed in the river water, in the reservoir water and also ultra-pure water and model river water were used. Ultra-pure water was selected as a control dispersive medium without organic matter and other natural compounds and the model RW was created to mimic the river water. The suspensions and nanoparticles were investigated using selected techniques such as Electrophoretic Light Scattering (ELS), Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (SEM/EDS), Atomic Force Microscopy (AFM), Brunauer-Emmett-Teller surface area analysis (BET), and the media were characterized based on their pH, Oxidation Reduction Potential (ORP), oxygen concentration, conductivity, temperature, Total Organic Carbon (TOC) and Total Phosphorus (TP). The results in general showed that all particles in the river or the reservoir water increased in diameter over one month. Natural compounds in real environmental media resulted in decrease of electrostatic repulsion and increase in diameter of aggregates. The nanoparticles dispersed in model river water did not behave in a similar way as in natural river water, probably due to lower concentration of TOC and higher conductivity. Moreover, as a consequence of larger size and higher density (about 1 ?m and 5 g/ml) of particles, the aggregates and strong sedimentation were observed. Experimental data revealed weakness of the DLS method for dynamic size distribution analysis of nanoparticles of higher density such as iron. The iron-based nanoparticles were too heavy and unstable in aqueous environment and therefore it was impossible to get reliable data. Nevertheless, DCS is a promising method for iron-based particle analysis. Finally, the toxicity of iron-based nanoparticles tested on Escherichia coli was not observed neither in newly prepared nor in aged nanoparticle suspensions.

Characterization of behaviour and transformation of nanomaterials in environmentally relevant media