Fenton and Photo-Fenton Nanocatalysts Revisited from the Perspective of Life Cycle Assessment

This study provides an overview of the environmental impacts associated with the production of different magnetic nanoparticles (NPs) based on magnetite (Fe3O4), with a potential use as heterogeneous Fenton or photo-Fenton catalysts in wastewater treatment applications. The tendency of Fe3O4 NPs to form aggregates in water makes necessary their decoration with stabilizing agents, in order to increase their catalytic activity. Different stabilizing agents were considered in this study: poly(acrylic acid) (PAA), polyethylenimine (PEI) and silica (SiO2), as well as the immobilization of the magnetite-based catalysts in a mesoporous silica matrix, SBA-15. In the case of photo-Fenton catalysts, combinations of magnetite NPs with semiconductors were evaluated, so that magnetic recovery of the nanomaterials is possible, thus allowing a safe discharge free of NPs. The results of this study suggest that magnetic nanoparticles coated with PEI or PAA were the most suitable option for their applications in heterogeneous Fenton processes, while ZnO-Fe3O4 NPs provided an interesting approach in photo-Fenton. This work showed the importance of identifying the relevance of nanoparticle production strategy in the environmental impacts associated with their useThis research was supported by two projects granted by Spanish Ministry of Science and Innovation: MODENA Project CTQ2016-79461-R and CLUSTERCAT Project MAT2015-67458-P, and Fundación Ramón Areces, Spain (Project CIVP18A3940). The authors belong to the Galician Competitive Research Groups ED431C-2017/22 and ED431C-2017/29 and CRETUS InstituteS

Environmental assessment of humic acid coated magnetic materials used as catalyst in photo-fenton processes

Persistent organic pollutants have been increasingly detected in natural waters, and this represents a real challenge to the quality of this resource. To remove these species, advanced treatment technologies are required. Among these technologies, Fenton-like and photo-Fenton-like processes have been investigated for the removal of pollutants from water. Delicate aspects of photo-Fenton processes are that light-driven processes are energy intensive and require a fair amount of chemical inputs, which strongly affects their overall environmental burdens. At present, aside from determining the efficiency of the processes to remove pollutants of a particular technology, it becomes fundamental to assess also the environmental sustainability of the overall process. In this work, the methodology of the life cycle assessment (LCA) was applied to identify the hotspots of using magnetite particles covered with humic acid (Fe3O4/HA) as a heterogeneous photo-Fenton catalyst for water remediation. The sustainability of the overall process was considered, and a comparative LCA study was performed between H2O2 and persulfate activation at different pH. The addition of humic substances to the particles allows the effectiveness of the catalyst to improve without increasing the environmental impacts; these processes are strongly correlated with energy consumption and therefore with the efficiency of the process. For this reason, working at acidic pH allows us to contain the impacts

Improving the sustainability of heterogeneous Fenton-based methods for micropollutant abatement by electrochemical coupling

Advanced oxidation processes such as Fenton reaction-based processes have attracted great interest in recent years as a promising alternative for the removal of persistent pollutants in wastewater. The use of nanocatalysts in advanced oxidation processes overcomes the limitations of homogeneous Fenton processes, where acidic pH values are required, and a large amount of sludge is generated after treatment. Aiming at maximizing the catalytic potential of the process, different configurations include coupling photocatalysis or electrochemistry to Fenton reactions. This manuscript presents a comparative environmental and economic analysis of different heterogeneous Fenton-based process using magnetic nanoparticles: Fenton, photo-Fenton, electro-Fenton and photoelectron-Fenton. These alternatives encompass not only different reaction conditions but also varying degradation kinetics, which control the treatment capability in each specific case. It is not only important to determine the technological feasibility of the proposal based on the removal performance of the target compounds, but also to identify the environmental profile of each configuration. In this regard, the Life Cycle Assessment methodology was applied considering a combination of primary and secondary data from process modeling. Moreover, and aiming towards the future large-scale implementation of the technology, an economic analysis of each configuration was also performed to provide a better understanding about the costs associated to the operation of Fenton-based wastewater treatmentsThis research was supported by HP-NANOBIO (PID2019-111163RB-I00), funded by Agencia Estatal de Investigación (AEI), and SPOTLIGHT (PDC2021-121540-I00) projects, funded by Agencia Estatal de Investigación (AEI) and European Union NextGenerationEU/PRTR. J.J.C. acknowledges Xunta de Galicia financial support through a postdoctoral fellowship (Grant reference ED481B-2021/015). S.E. and J.G.-R. predoctoral fellowships were funded by Agencia Estatal de Investigación (AEI) and by “ESF Investing in your future” (Grant references PRE2020-092074 and FPU19/004612, respectively). The authors belong to the Galician Competitive Research Group (GRC) ED432C-2021/37S

Synthesis of magnetic fe3o4/znwo4 and fe3o4/znwo4/cevo4 nanoparticles: The photocatalytic effects on organic pollutants upon irradiation with uv-vis light

Magnetic Fe3O4/ZnWO4 and Fe3O4/ZnWO4/CeVO4 nanoparticles with different molar ratios of CeVO4 to other inorganic components were synthesized through co-precipitation with a sonochemical-assisted method. X-ray diffraction, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, ultraviolet-visible diffuse reflectance spectroscopy, vibrating sample magnetometry, and scanning electron microscopy (SEM) methods were used for the physico�chemical characterization of the obtained nanoparticles. As shown in the SEM images, the average sizes of the Fe3O4 /ZnWO4 and Fe3O4 /ZnWO4 /CeVO4 nanoparticles that formed aggregates were approximately 50�70 nm and 80�100 nm, respectively. The photocatalytic performance of these nanoparticles was examined by measuring methylene blue degradation under visible light (assisted by H2O2). The sample with a mass ratio of 1:2:1 (Fe3O4/ZnWO4/CeVO4, S4) exhibited optimal photocatalytic performance, and thus this sample was subsequently used for the photodegradation of different organic pollutants upon irradiation with ultraviolet (UV) and visible light. Approximately 90 and 70 degradation of methyl violet and methylene blue, respectively, was observed after visible light irradiation. Additionally, the mechanism of the photocatalytic reaction was investigated by measuring ·OH release under UV light in a system with terephthalic acid and by measuring the release of·O2 �,·OH, and hole scavengers. © 2020 by the authors. Licensee MDPI, Basel, Switzerland

Synthesis of magnetic fe3o4/znwo4 and fe3o4/znwo4/cevo4 nanoparticles: The photocatalytic effects on organic pollutants upon irradiation with uv-vis light

Magnetic Fe3O4/ZnWO4 and Fe3O4/ZnWO4/CeVO4 nanoparticles with different molar ratios of CeVO4 to other inorganic components were synthesized through co-precipitation with a sonochemical-assisted method. X-ray diffraction, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, ultraviolet-visible diffuse reflectance spectroscopy, vibrating sample magnetometry, and scanning electron microscopy (SEM) methods were used for the physico�chemical characterization of the obtained nanoparticles. As shown in the SEM images, the average sizes of the Fe3O4 /ZnWO4 and Fe3O4 /ZnWO4 /CeVO4 nanoparticles that formed aggregates were approximately 50�70 nm and 80�100 nm, respectively. The photocatalytic performance of these nanoparticles was examined by measuring methylene blue degradation under visible light (assisted by H2O2). The sample with a mass ratio of 1:2:1 (Fe3O4/ZnWO4/CeVO4, S4) exhibited optimal photocatalytic performance, and thus this sample was subsequently used for the photodegradation of different organic pollutants upon irradiation with ultraviolet (UV) and visible light. Approximately 90 and 70 degradation of methyl violet and methylene blue, respectively, was observed after visible light irradiation. Additionally, the mechanism of the photocatalytic reaction was investigated by measuring ·OH release under UV light in a system with terephthalic acid and by measuring the release of·O2 �,·OH, and hole scavengers. © 2020 by the authors. Licensee MDPI, Basel, Switzerland

Fenton and Photo-Fenton Nanocatalysts Revisited from the Perspective of Life Cycle Assessment

This study provides an overview of the environmental impacts associated with the production of different magnetic nanoparticles (NPs) based on magnetite (Fe3O4), with a potential use as heterogeneous Fenton or photo-Fenton catalysts in wastewater treatment applications. The tendency of Fe3O4 NPs to form aggregates in water makes necessary their decoration with stabilizing agents, in order to increase their catalytic activity. Different stabilizing agents were considered in this study: poly(acrylic acid) (PAA), polyethylenimine (PEI) and silica (SiO2), as well as the immobilization of the magnetite-based catalysts in a mesoporous silica matrix, SBA-15. In the case of photo-Fenton catalysts, combinations of magnetite NPs with semiconductors were evaluated, so that magnetic recovery of the nanomaterials is possible, thus allowing a safe discharge free of NPs. The results of this study suggest that magnetic nanoparticles coated with PEI or PAA were the most suitable option for their applications in heterogeneous Fenton processes, while ZnO-Fe3O4 NPs provided an interesting approach in photo-Fenton. This work showed the importance of identifying the relevance of nanoparticle production strategy in the environmental impacts associated with their use