Ecotoxicity of, and remediation with, engineered inorganic nanoparticles in the environment

Financial support was provided by the Spanish Ministerio de Medio Ambiente y Medio Rural y Marino (Project Exp. 007/RN08/03.1).This article presents recent developments on the use of inorganic nanoparticles (NPs) for environmental remediation in polluted soil, water and gas. The number of publications on these topics has grown exponentially in recent years, especially those focused on wastewater treatment. Among these topics, removal of metals has become the most popular, although some works relate to the use of nanomaterials for the elimination of nutrients (e.g., nitrogen and some persistent organic pollutants). However, this growth has not been accompanied by knowledge about the behavior of NPs once used and released into the environment. In this article, we also comment upon the current situation with respect to NP toxicology (nanotoxicology). A remarkable number of different toxicology tests has been applied to NPs, often making it very difficult to interpret or to generalize the results. We analyze in detail the bioluminescence, Daphnia magna and other tests, and give some preliminary results obtained in our work

Preliminary study of phosphate adsorption onto cerium oxide nanoparticles for use in water purification : nanoparticles synthesis and characterization

In this study, the synthesis and characterization of cerium oxide nanoparticles (CeO₂-NPs) and their adsorption potential for removing phosphate from water was evaluated using a multi-factor experimental design to explore the effect of various factors on adsorption. The objective function selected was the percentage of phosphate removed from water, in which the phosphate concentration and the CeO₂-NP concentration are quantitative variables (factors in the experimental design). A lineal polynomial fitted the experimental results well (R² = 0.9803). The nanostructure was studied by transmission electron microscopy (TEM) and high-resolution TEM techniques before and after the adsorption process. During the adsorption and desorption processes several changes in the morphology and surface chemistry of the CeO₂-NPs were observed

Chromium VI adsorption on cerium oxide nanoparticles and morphology changes during the process

Financial support was provided by the Spanish Ministerio de Medio Ambiente y Medio Rural y Marino (Project Exp. 007/RN08/03.1). Sonia Recillas and Joan Colón thank Universitat Autònoma de Barcelona for the award of a post-doctoral and pre-doctoral fellowship respectively..In this study, suspended cerium oxide nanoparticles stabilized with hexamethylenetetramine were used for the removal of dissolved chromium VI in pure water. Several concentrations of adsorbent and adsorbate were tested, trying to cover a large range of possible real conditions. Results showed that the Freundlich isotherm represented well the adsorption equilibrium reached between nanoparticles and chromium, whereas adsorption kinetics could be modeled by a pseudo-second-order expression. The separation of chromium-cerium nanoparticles from the medium and the desorption of chromium using sodium hydroxide without cerium losses was obtained. Nanoparticles agglomeration and morphological changes during the adsorption-desorption process were observed by TEM. Another remarkable result obtained in this study is the low toxicity in the water treated by nanoparticles measured by the Microtox® commercial method. These results can be used to propose this treatment sequence for a clean and simple removal of drinking water or wastewater re-use when a high toxicity heavy metal such as chromium VI is the responsible for water pollution

Use of CeO₂, TiO₂ and Fe₃O₄ nanoparticles for the removal of lead from water : toxicity of nanoparticles and derived compounds

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.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

Ecotoxicity of, and remediation with, engineered inorganic nanoparticles in the environment

Financial support was provided by the Spanish Ministerio de Medio Ambiente y Medio Rural y Marino (Project Exp. 007/RN08/03.1).This article presents recent developments on the use of inorganic nanoparticles (NPs) for environmental remediation in polluted soil, water and gas. The number of publications on these topics has grown exponentially in recent years, especially those focused on wastewater treatment. Among these topics, removal of metals has become the most popular, although some works relate to the use of nanomaterials for the elimination of nutrients (e.g., nitrogen and some persistent organic pollutants). However, this growth has not been accompanied by knowledge about the behavior of NPs once used and released into the environment. In this article, we also comment upon the current situation with respect to NP toxicology (nanotoxicology). A remarkable number of different toxicology tests has been applied to NPs, often making it very difficult to interpret or to generalize the results. We analyze in detail the bioluminescence, Daphnia magna and other tests, and give some preliminary results obtained in our work

Use of CeO₂, TiO₂ and Fe₃O₄ nanoparticles for the removal of lead from water : toxicity of nanoparticles and derived compounds

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.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

Chromium VI adsorption on cerium oxide nanoparticles and morphology changes during the process

Financial support was provided by the Spanish Ministerio de Medio Ambiente y Medio Rural y Marino (Project Exp. 007/RN08/03.1). Sonia Recillas and Joan Colón thank Universitat Autònoma de Barcelona for the award of a post-doctoral and pre-doctoral fellowship respectively..In this study, suspended cerium oxide nanoparticles stabilized with hexamethylenetetramine were used for the removal of dissolved chromium VI in pure water. Several concentrations of adsorbent and adsorbate were tested, trying to cover a large range of possible real conditions. Results showed that the Freundlich isotherm represented well the adsorption equilibrium reached between nanoparticles and chromium, whereas adsorption kinetics could be modeled by a pseudo-second-order expression. The separation of chromium-cerium nanoparticles from the medium and the desorption of chromium using sodium hydroxide without cerium losses was obtained. Nanoparticles agglomeration and morphological changes during the adsorption-desorption process were observed by TEM. Another remarkable result obtained in this study is the low toxicity in the water treated by nanoparticles measured by the Microtox® commercial method. These results can be used to propose this treatment sequence for a clean and simple removal of drinking water or wastewater re-use when a high toxicity heavy metal such as chromium VI is the responsible for water pollution

Potential use of CeO₂, TiO₂ and Fe₃O₄ nanoparticles for the removal of cadmium from water

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.Inorganic nanoparticles (NPs) of cerium oxide (CeO₂), iron oxide (Fe₃O₄) and titanium oxide (TiO₂) were studied for the removal of dissolved cadmium from water at concentrations ranging from 25 to 350 mg/L. Adsorption was the predominant mechanism for sequestration, and particularly efficient cadmium removal was demonstrated for Fe₃O₄ NPs. Experimental data were fitted to three different adsorption isotherms: Langmuir, Freundlich and Temkin. The best fit was obtained for the Freundlich isotherm (R² > 0.96 for all NPs). Adsorption was shown to follow pseudo second-order kinetics (R² ⩾ 0.91 for all NPs). All three NPs showed some removal of cadmium in aqueous solution, but after 72 h of process, Fe₃O₄ NPs showed a higher capacity of cadmium adsorption (101.1 mg Cd/g NP) than CeO₂ NPs (49.1 mg Cd/g NP) or TiO₂ NPs (12.2 mg Cd/g NP). These results demonstrate the potential use of this NPs to remove dissolved cadmium at high concentrations