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In this study, the synthesis and characterization of cerium oxide nanoparticles (CeO(2)-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 CeO(2)-NP concentration are quantitative variables (factors in the experimental design). A lineal polynomial fitted the experimental results well (R(2) = 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 CeO(2)-NPs were observed.

Thermochromic smart windows have been extensively investigated due to two main benefits: first, the comfort for people in a room through avoiding high temperatures resulting from solar heating while taking advantage of the visible light, and second, the energy efficiency saving offered by using those systems. Vanadium dioxide (VO2) is one of the most used materials in the development of thermochromic devices. The countries located in the tropics show little use of these technologies, although studies indicate that due to their characteristics of solar illumination and temperature, they could benefit greatly. To optimize and achieve maximum benefit, it is necessary to design a window that adjusts to tropical conditions and at the same time remains affordable for extensive implementation. VO2 nanoparticles embedded in polymeric matrices are an option, but improvements are required by means of studying different particle sizes, dopants and polymeric matrices. The purpose of this review is to analyze what has been regarding toward the fabrication of smart windows based on VO2 embedded in polymeric matrices for tropical areas and provide a proposal for what this device must comply with to contribute to these specific climatic needs. [ABSTRACT FROM AUTHOR]

The study of the efficiency of the magnetic separation of nanoparticles in environment is important for its implementation in the remediation of water bodies. In this work the sedimentation dynamics of Glutathione@MNPswere evaluated for water systems with addition of calcium, zinc and sodium ions in a concentration range of 0-40 mg/L in the presence and absence of a vertical magnetic field of 0.2 T. Also, critical coagulation concentrations (CCC) were determined based on the DLVO theory. Particles stability in the absence of metal ions higher than 8 weeks could be observed, whereas in the presence of these ions the stability was reduced to 8 weeks. Separation of the material from the aqueous phase higher than 90% was obtained both for the presence of ions and for the material after the addition of heavy metals such as Hg and Cr. [ABSTRACT FROM AUTHOR]

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 (101.1mg Cd/g NP) than CeO2 NPs (49.1mg Cd/g NP) or TiO2 NPs (12.2mg Cd/g NP). These results demonstrate the potential use of this NPs to remove dissolved cadmium at high concentrations. [ABSTRACT FROM AUTHOR]

Abstract: 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: 189mg Pb/g NPs CeO2, 83mg Pb/g NPs Fe3O4 and 159mg 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. [Copyright &y& Elsevier]

Abstract: Growth in production and use of nanoparticles (NPs) will result increased concentrations of these in industrial and urban wastewaters and, consequently, in wastewater-treatment facilities. The effect of this increase on the performance of the wastewater-treatment process has not been studied systematically and including all the microbial communities involved in wastewater treatment. The present work investigates, by using respiration tests and biogas-production analysis, the inhibitory effect of four different commonly used metal oxide (CeO2 and TiO2) and zero-valent metal (Ag and Au) nanoparticles on the activity of the most important microbial communities present in a modern wastewater-treatment plant. Specifically, the actions of ordinary heterotrophic organisms, ammonia oxidizing bacteria, and thermophilic and mesophilic anaerobic bacteria were tested in the presence and absence of the nanoparticles. In general, CeO2 nanoparticles caused the greatest inhibition in biogas production (nearly 100%) and a strong inhibitory action of other biomasses; Ag nanoparticles caused an intermediate inhibition in biogas production (within 33–50%) and a slight inhibition in the action of other biomasses, and Au and TiO2 nanoparticles caused only slight or no inhibition for all tested biomasses. [Copyright &y& Elsevier]

Abstract: In this study, several standard toxicity tests have been performed on selected inorganic nanoparticles. Acute toxicity tests were selected according to their extensive use in toxicological studies and included phytotoxicity using several seeds, Daphnia magna and a bioluminescent test (Microtox®). All of them have been used in several international regulations as toxicity assays. In the case of nanoparticles (NPs), we have studied those of cerium oxide, titanium dioxide and iron oxide. Iron oxide NPs are well known and broadly used and were selected because of their low toxicity. Titanium dioxide and cerium oxide NPs are currently being used in several fields such as photocatalysis and medical applications, but their toxicity effects have been scarcely studied. Our results revealed that cerium NPs are extremely toxic in the entire set of tests conducted (inhibition higher than 80% at very low concentrations for the bioluminescence test and LC50=0.012mg/ml of mortality in the assays of D. magna), whereas titanium NPs were practically inert in terms of toxicity (values similar to those of controls). The possible toxicological effect of the solvents necessary to stabilize NPs in liquid medium for the three cases (stabilizers) has been also studied. Only in the germination test (phytotoxicity) of some seeds they showed some detrimental effect to germination. In general, the standardized tests proposed in this study have proved to be very useful in the determination of NPs toxicity when no or few data are available, although further work is necessary in the case of the germination test. [Copyright &y& Elsevier]

Abstract: 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. [Copyright &y& Elsevier]

Abstract: 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. [ABSTRACT FROM AUTHOR]