Financial support was provided by the Spanish Ministerio de Medio Ambiente y Medio Rural y Marino (Project Exp. 007/RN08/03.1). Sonia Recillas thanks Universitat Autònoma de Barcelona for the award of a post-doctoral fellowship.

Altres ajuts: MAPAMA/007/RN08/03.1

Nanoparticles (NPs) suspensions of CeO₂, Fe₃O₄ and TiO₂ were synthesized and tested for lead removal in water cleaning processes. The results obtained are promising for the use of these NPs in lead elimination via adsorption process. The adsorption capacity obtained for the NPs was: 189 mg Pb/g NPs CeO₂, 83 mg Pb/g NPs Fe3O4 and 159 mg Pb/g NPs TiO₂. Another important issue assessed in this study was to determine the toxicity of the NPs in each step of the process: synthesized NPs, NPs after lead adsorption and the supernatant after NPs separation. In order to study the interaction with living organisms and prevent future environmental damages, the Germination test in Tomato (Lycopersicom esculentum), Lettuce (Lactuca sativa), Cucumber (Cucumis sativus) seeds and the Microtox® assay, based on the use of bioluminescent marine bacterium, Photobacterium phosphoreum/Vibrio fischeri, were used to evaluate the toxicity of these materials. The CeO₂ NPs showed a high level of lead removal although presented a high phytotoxicity. The TiO₂ NPs inhibited the lead toxicity against the marine bacterium. Interestingly, the media used to stabilize the NPs (tetramethylammonium hydroxide and hexamethylenetetramine) presented a significant reduction in the germination index. TiO₂ and Fe₃O₄ NPs did not exhibit any toxicity and could be used as absorbents for Pb (II) removal.