Application of green zero-valent iron nanoparticles to the remediation of soils contaminated with ibuprofen

Abstract

Zero-valent iron nanoparticles (nZVIs) are often used in environmental remediation. Their high surface area that is associated with their high reactivity makes them an excellent agent capable of transforming/degrading contaminants in soils and waters. Due to the recent development of green methods for the production of nZVIs, the use of this material became even more attractive. However, the knowledge of its capacity to de-grade distinct types of contaminants is still scarce. The present work describes the study of the application of green nZVIs to the remediation of soils contami-nated with a common antiinflammatory drug, ibuprofen. The main objectives of this work were to produce nZVIs using extracts of grape marc, black tea and vine leaves, to verify the degradation of ibuprofen in aque-ous solutions by the nZVIs, to study the remediation process of a sandy soil contaminated with ibuprofen using the nZVIs, and to compare the experiments with other common chemical oxidants. The produced nZVIs had nanometric sizes and were able to degrade ibuprofen (54 to 66% of the initial amount) in aqueous solutions. Similar remediation efficiencies were obtained in sandy soils. In this case the remediation could be enhanced (achieving degradation efficiencies above 95%) through the complemen-tation of the process with a catalyzed nZVI Fenton-like reaction. These results indicate that this remediation technology represents a good alternative to traditional and more aggressive technologies.

Characterization of green zero-valent iron nanoparticles produced with tree leaf extracts

“…Once more it can be concluded that different extracts with similar antioxidant capacities can interact differently with the nZVIs, also affecting their reactivity. This is supported by Machado et al (2013b) who observed that the extracts of pear and lemon leaves have low antioxidant capacities, but in this work they presented very different reactivities. Huang et al (2014) evaluated the reactivity of nZVIs synthesized using three different tea leaves (green, oolong and black) and also observed different behaviors that were attributed to the caffeine/polyphenol content that acted as both reducing and capping agents.…”

“…To evaluate the agglomeration behavior of the green nZVI the following tests were performed: the different nZVIs were produced according to the most favorable conditions (extraction temperature, contact time and mass of leaves:solvent volume ratio) described in Machado et al (2013b), and their agglomeration (settlement) was monitored through spectrophotometric analysis for 90 min, considering the time of the highest reactivity of nZVI. With these tests it was possible to identify which was the nZVI concentration, for each extract used, at which the settling occurred after 90 min, therefore guaranteeing that the nZVIs were in suspension during their reactive period.…”

“…Among the most common nanomaterials, zero-valent iron nanoparticles (nZVI) are one of the most widely used and have proven to be extremely effective for the removal of a wide range of pollutants such as pharmaceutical products (Machado et al, 2013b), chlorinated solvents (Choe et al, 2001), metals (Klimkova et al, 2011) among others (Crane and Scott, 2012).…”

“…This method uses aqueous extracts with high reduction capacities which are obtained from natural products, such as tea leaves (Hoag et al, 2009) or tree and bush leaves (Machado et al, 2013b). The use of these extracts provides several advantages when compared to the traditional method: i) the polyphenolic matrix can act as a capping agent that protects the iron nanoparticles from premature oxidation (Hoag et al, 2009) and agglomeration, ii) it can be used as a source of nutrients and microorganisms for a possible bioremediation action after the chemical treatment (Machado et al, 2013b) and iii) the valorization of natural products, such as tree leaves, that, in some cases, are considered wastes or do not have any added value (Machado et al, 2013b). Martins et al (unpublished results) used life cycle assessment to evaluate the environmental performance of the two synthesis methods (traditional using the sodium borohydride and the green using natural extracts) and concluded that the green synthesis method presents lower environmental impacts than the traditional method.…”

An overview on heterogeneous Fenton and photoFenton reactions using zerovalent iron materials

“…The degradation process in sandy soil was slower than that in aqueous solution due to the time required for percolation. The combination of these nanoparticles in a Fenton reaction showed improved efficiency up to 95 % [131].…”