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- LCA applied to nano scale zero valent iron synthesisPublication . Martins, Florinda; Machado, Susana; Albergaria, José Tomás; Delerue-Matos, CristinaPurpose Application of zero valent iron nanoparticles is an innovative technology for ground water treatment and soil remediation. There are several methods to synthesise nano scale zero valent iron (nZVI), namely through bottom-up methods which consists on chemical reactions using strong reducing agents. In this work, the environmental impacts and costs were determined for two methods, namely the traditional one that uses sodium borohydride and the green method that uses extracts obtained from natural products. Methods The consideration of environment and economic aspects in the earlier stages of the synthesis processes and in the development of new materials is of great importance since it can help to decide if alternative methods are promising and should be further developed aiming more sustainable processes. In this work, life cycle assessment (LCA) was used as an ecodesign strategy evaluating environmental performance of the two synthesis methods, identifying critical stages of the synthesis processes of nZVI. An economic evaluation and a sensitivity analysis considering a different scenario for electricity production were also performed. Results and discussion The results obtained in this study showed that the green synthesis method presents lower environmental impacts than the traditional one, roughly 50% lower in the first scenario. In the second scenario, environmental impact of green synthesis corresponds to 38% of the environmental impact of traditional synthesis. In the green method, the critical stage is the extraction process which is closely related to the electricity production. In the traditional method, the reactant use is the critical stage that is related to the production of sodium borohydride. The economic evaluation indicated that the traditional synthesis method is much more expensive than the green synthesis (roughly eight times higher). Conclusions From the results obtained, it is possible to conclude that the green synthesis method presents lower environmental impacts in both scenarios and lower costs than the traditional synthesis.
- Green zero-valent iron nanoparticles for the degradation of amoxicillinPublication . Machado, S.; Nouws, H. P. A.; J.T., Albergaria; Delerue-Matos, CristinaIn the last years, it has been proven that zerovalent iron nanoparticles, including those produced using green methods, are efficient remediation agents for a wide range of target contaminants. However, apart from the known advantages of these green nanomaterials, the knowledge of how they act on distinct contaminants is not yet fully understood and requires further investigation. The objectives of this work were to study the degradation of a common antibiotic, amoxicillin, in water and in a sandy soil using green zero-valent iron nanoparticles (gnZVIs) as reductants and as catalysts for the Fenton reaction. It represents the first study of the use of gnZVI, as alternative for the zero-valent iron nanoparticles produced with sodium borohydride, for the degradation of amoxicillin. The results of the performed tests indicate that gnZVIs have the potential to be used in remediation processes. In both chemical tests, the gnZVI was able to degrade up to 100% of amoxicillin in aqueous solutions, using an amoxicillin/ gnZVI molar ratio of 1:15 when applied as a reductant, and an amoxicillin/H2O2/gnZVI molar ratio of 1:13:1 when applied as a catalyst for the Fenton reaction. The soil tests showed that the required molar ratios for near complete degradation were higher in the reduction test (1:150) than in the gnZVI-catalyzed Fenton reaction (1:1290:73). This is possibly due to parallel reactions with the soil matrix and/or limitations of the reagents to reach the entire soil sample. The degradation efficiencies obtained in these tests were 55 and 97% for the reduction and catalyzed Fenton processes, respectively.
- Green zero valent iron nanoparticles dispersion through a sandy column using different injection sequencesPublication . Soares, António Alves; Ramos, Sandra; Albergaria, José Tomás; Delerue-Matos, CristinaThe contamination of soils is a global environmental problem that urges an increased effort to recover polluted sites. In Europe, there are an estimated 20,000 polluted sites that need to be remediated and around 350,000 sites that are classified as potentially contaminated by the European Environment Agency (EEA). Remediation is a part of the solution to this problem, requiring the most innovative and sustainable technologies. In this context, the use of zero valent iron nanoparticles (nZVI) is a promising, low cost and efficient technology for the remediation of soil and groundwater contaminated with a wide range of organic and inorganic pollutants. Among the nZVIs, the ones produced using Green synthesis methods (green nZVIs (gnZVI)) using natural extracts, such as green tea, are increasingly considered an alternative technology for the future. However, there are issues related to the application of gnZVI in soil that are still not fully understood, requiring further research, among these is the study of their transport in soils. Therefore, this work aims to study the transport of gnZVIs in sandy soils under diverse conditions such as soil particle size, soil saturation level and injection sequence. Several experiments were performed in an acrylic column with two sandy soils with different particle sizes (between 0.5 and 1.0 mm and higher than 1.0 mm), using two distinct water saturation conditions (saturated and dry) and four injection sequences. After these tests the distribution of the gnZVI along the soil column was determined by atomic absorption spectroscopy. This work allowed concluding that the injection sequence might be one of the most important factors influencing the rate of nZVI dispersion through a sandy column. According to the results it was possible to propose, for distinct types of contamination (deep, superficial, hot spot or dispersed), the most appropriate injection sequence.