New Challenges in the Application of Advanced Oxidation Processes
Magnetite (Fe3O4), a core-shell material (SiO2@Fe3O4), and reduced graphene oxide-Fe3O4 (referred as rGO-MN) were used as supports of a specific highly active TiO2 photocatalyst. Thermal treatments at 200 or 450 °C, different atmospheres (air or N2), and TiO2:support weight ratios (1.0, 1.5, or 2.0) were investigated. X-ray diffractograms revealed that magnetite is not oxidized to hematite when the core-shell SiO2@Fe3O4 material—or a N2 atmosphere (instead of air) in the thermal treatment—was employed to prepare the TiO2-based catalysts (the magnetic properties being preserved). The materials treated with N2 were first tested for degradation of imazalil (a well-known fungicide) in deionized water. The best compromise between the photocatalytic activity, magnetic separation, and Fe leached (1.61 mg L−1, i.e., below the threshold for water reuse in irrigation) was found for the magnetic catalyst prepared with SiO2@Fe3O4, an intermediate TiO2:support ratio (1.5), and treated at 200 °C under N2 atmosphere (i.e., SiO2@Fe3O4-EST-1.5-200-N2). This material was then tested for the treatment of imazalil in a synthetic wastewater, SW (with a chemical composition simulating an effluent resulting from fruit postharvest activity). This SW has a pH of 4.2 and the experiments were carried out at this natural pH0 and at neutral conditions (keeping pH at 7 along the reaction). The magnetic catalyst was more active than bare TiO2 for the treatment of imazalil in SW at natural pH. Since Fe leaching was observed (3.53 mg L−1), added H2O2 enhanced both imazalil degradation and mineralization. Conveniently, these catalysts can be readily recovered by using a conventional magnetic field, as demonstrated over three consecutive recycling runs.
Imazalil Photocatalysis TiO2Magnetic Fe3O4SiO2
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The Ministry of Economy and Competitiveness (MINECO), Government of Spain, is thanked for funding of the NANOBAC project (IPT-2011-1113-310000) and co-funding, together with the European Regional Development Fund (ERDF) for the Infrastructure Project 2010-3EUNLP10-3E-726. DES would like to thank the University of Las Palmas de Gran Canaria (ULPGC) for funding (PhD Grant Program) and the Spanish Ministry of Science and Innovation (MICINN) for its financial support through the PhD Studentship BES-2010-036537. This research was also partially supported by Project POCI-01-0145-FEDER-006984–Associate Laboratory LSRE-LCM funded by FEDER through COMPETE2020–Programa Operacional Competitividade e Internacionalização (POCI), and by national funds through FCT–Fundação para a Ciência e a Tecnologia, the Strategic Funding UID/Multi/04423/2013 through national funds provided by FCT–Foundation for Science and Technology and European Regional Development Fund (ERDF), in the framework of the programme PT2020. The authors also thank the Canarian fruit postharvest companies for their collaboration. AMTS and LMPM acknowledge the FCT Investigator Programme (IF/01501/2013 and IF/01248/2014), with financing from the European Social Fund and the Human Potential Operational Programme. LMPM also acknowledges the MINECO and the European Social Fund for a Ramon y Cajal research contract (RYC-2016-19347).
Bandara J, Mielczarski JA, Lopez A, Kiwi J (2001) Sensitized degradation of chlorophenols on iron oxides induced by visible light. Comparison with titanium oxide. Appl Catal B Environ 34:321–333CrossRefGoogle Scholar
Du W, Xu Y, Wang Y (2008) Photoinduced degradation of orange II on different iron (Hydr) oxides in aqueous suspension: rate enhancement on addition of hydrogen peroxide, silver nitrate, and sodium fluoride. Langmuir 24:175–181CrossRefGoogle Scholar
Ferroudj N, Nzimoto J, Davidson A, Talbot D, Briot E, Dupuis V, Bée A, Medjram MS, Abramson S (2013) Maghemite nanoparticles and maghemite/silica nanocomposite microspheres as magnetic Fenton catalysts for the removal of water pollutants. Appl Catal B Environ 136–137:9–18. https://doi.org/10.1016/j.apcatb.2013.01.046CrossRefGoogle Scholar
Pastrana-Martínez LM, Morales-Torres S, Likodimos V, Figueiredo JL, Faria JL, Falaras P, Silva AMT (2012) Advanced nanostructured photocatalysts based on reduced graphene oxide–TiO2 composites for degradation of diphenhydramine pharmaceutical and methyl orange dye. Appl Catal B Environ 123–124:241–256. https://doi.org/10.1016/j.apcatb.2012.04.045CrossRefGoogle Scholar
Rivera-Utrilla J, Bautista-Toledo I, Ferro-García MA, Moreno-Castilla C (2001) Activated carbon surface modifications by adsorption of bacteria and their effect on aqueous lead adsorption. J Chem Technol Biotechnol 76:1209–1215. https://doi.org/10.1002/jctb.506CrossRefGoogle Scholar
Santiago DE, Doña-Rodríguez JM, Araña J, Fernández-Rodríguez C, González-Díaz O, Pérez-Peña J, Silva AMT (2013) Optimization of the degradation of imazalil by photocatalysis: comparison between commercial and lab-made photocatalysts. Appl Catal B Environ 138–139:391–400. https://doi.org/10.1016/j.apcatb.2013.03.024CrossRefGoogle Scholar
Santiago DE, Araña J, González-Díaz O, Alemán-Dominguez ME, Acosta-Dacal AC, Fernandez-Rodríguez C, Pérez-Peña J, Doña-Rodríguez JM (2014) Effect of inorganic ions on the photocatalytic treatment of agro-industrial wastewaters containing imazalil. Appl Catal B Environ 156–157:284–292. https://doi.org/10.1016/j.apcatb.2014.03.022CrossRefGoogle Scholar
Smolensky ED, Park HY, Zhou Y, Rolla GA, Marjańska M, Botta M, Pierre VC (2013) Scaling laws at the nano size: the effect of particle size and shape on the magnetism and relaxivity of iron oxide nanoparticle contrast agents. J Mater Chem B Mater Biol Med 1:2818–2828. https://doi.org/10.1039/C3TB00369HCrossRefGoogle Scholar
Yang H, Finlayson-Pitts BJ (2001) Infrared spectroscopic studies of binary solutions of nitric acid and water and ternary solutions of nitric acid, sulfuric acid, and water at room temperature: evidence for molecular nitric acid at the surface. J Phys Chem A 105:1890–1896. https://doi.org/10.1021/jp004224fCrossRefGoogle Scholar