Unexpected activity of magnetically separable Fenton catalyst in clay slurries

ABSTRACT

Maghemite/silica nanocomposite microspheres (γ-Fe₂O₃/SiO₂ MS) have been tested as magnetically separable heterogeneous Fenton catalyst in beidellite clay slurries in the presence of methylorange (MO) as a model pollutant. Due to its strong magnetic susceptibility, the catalyst was easily recovered from the clay slurries by a selective magnetic sorting, even in highly concentrated slurries. The Fenton oxidation of MO was strongly enhanced in the clay slurries in comparison to the reaction in aqueous phase, highlighting a synergistic catalytic effect. The influence of different experimental parameters such as the presence of specific Reactive Oxygen Species (ROS) scavengers, pH, H₂O₂, catalyst and clay concentrations, on the catalytic activity was also evaluated. Contrary to what was observed in aqueous phase, generation of hydroxyl radicals via the Haber–Weiss mechanism was not the unique pathway that caused MO degradation in the beidellite slurries. We also observed that the synergistic effect is more marked at pH near neutrality and low amounts of H₂O₂ and clay. Furthermore, the unchanged activity of the catalyst during five successive cycles together with the low level of iron leaching, makes it suitable candidate for an application as a magnetic heterogeneous Fenton catalyst in wastewater treatment, especially for surface waters or sludges naturally containing fine clay particles.

GRAPHICAL ABSTRACT

KEYWORDS:

• Heterogeneous Fenton
• magnetic nanocomposite microspheres
• beidellite clay
• magnetic selective sorting
• water-treatment

Acknowledgments

We are very thankful to Emmanuel Aubry, David Montero, Aude Michel and Delphine Talbot for their technical support, Sofia Housni for the help and the cooperation during the research and Anne Davidson and Laurent Michot for the fruitful discussions. We also thank all the team of the research laboratory ‘Laboratoire de Génie Chimique et Environnement de Skikda’ (LGCES) and the team of ‘Laboratoire de PHysico-chimie des Electrolytes et Nanosystèmes InterfaciauX’ (PHENIX) for the help and the availability shown in the development of this work.

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Ibtissam Boussouf http://orcid.org/0000-0003-1998-1438