Environmental Science and Pollution Research

, Volume 25, Issue 28, pp 27724–27736 | Cite as

TiO2-based (Fe3O4, SiO2, reduced graphene oxide) magnetically recoverable photocatalysts for imazalil degradation in a synthetic wastewater

  • Dunia E. SantiagoEmail author
  • Luisa M. Pastrana-Martínez
  • Elisenda Pulido-Melián
  • Javier Araña
  • Joaquim L. Faria
  • Adrián M. T. Silva
  • Óscar González-Díaz
  • José M. Doña-RodríguezEmail author
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.

Graphical abstract

% Imazalil conversion using different magnetic catalysts and comparison with bare TiO2


Imazalil Photocatalysis TiO2 Magnetic Fe3O4 SiO2 



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).

Supplementary material

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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2018

Authors and Affiliations

  • Dunia E. Santiago
    • 1
    • 2
    Email author
  • Luisa M. Pastrana-Martínez
    • 3
  • Elisenda Pulido-Melián
    • 1
  • Javier Araña
    • 1
  • Joaquim L. Faria
    • 4
  • Adrián M. T. Silva
    • 4
  • Óscar González-Díaz
    • 1
  • José M. Doña-Rodríguez
    • 1
    Email author
  1. 1.Grupo FEAM, Unidad Asociada al CSIC (a través del ICCMM de Sevilla)i-UNAT - Universidad de Las Palmas de Gran Canaria, Edificio del Parque Científico Tecnológico de la ULPGCLas PalmasSpain
  2. 2.Dpto. de Ingeniería de ProcesosUniversidad de Las Palmas De Gran Canaria, Campus Universitario de TafiraLas PalmasSpain
  3. 3.Carbon Materials Research Group, Department of Inorganic Chemistry, Faculty of SciencesUniversity of Granada, Campus Fuentenueva s/nGranadaSpain
  4. 4.Laboratory of Separation and Reaction Engineering—Laboratory of Catalysis and Materials (LSRE-LCM), Faculdade de EngenhariaUniversidade do PortoPortoPortugal

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