A ferromagnetic γ-alumina-supported iron catalyst for CWPO. Application to chlorophenols

A ferromagnetic γ-Al2O3-supported iron catalyst has been prepared and its activity and stability in catalytic wet peroxide oxidation (CWPO) have been compared with those of a previous iron-based conventional catalyst using the same support. Both catalysts were characterized by nitrogen adsorption–desorption isotherms, ICP, TXRF, XRD, XPS, elemental analysis and Mössbauer spectroscopy. The behavior of these catalysts in CWPO of chlorophenols has been related with the nature of the dominant iron species (magnetite or hematite). The results showed that the magnetic catalyst improved significantly the decomposition of H2O2 leading to an increased degradation and mineralization of chlorophenols. Complete conversion of those target pollutants and more than 75% TOC reduction were achieved after 4 h under stoichiometric H2O2 dose, 100 mg L−1 initial chlorophenol concentration, 1 g L−1 catalyst, pH 3 and 50 °C temperature. Moreover, complete dechlorination of all the chlorophenols tested was achieved, being the residual organic by-products short-chain acids without significance in terms of ecotoxicity. The catalyst showed a remarkable stability in long-term continuous experiments with limited Fe leaching, below 5% of the initial loading after 100 h on stream. An additional clear advantage of the new catalyst is its easy separation and recovery from the reaction medium by applying an external magnetic field.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Short and simple procedure for synthesizing a new magnetic catalyst (Fe3O4/γ-Al2O3). ► The ferromagnetic catalyst is highly active and stable upon CWPO of chlorophenols. ► The complete conversion and dechlorination of chlorophenols and 75% mineralization is reached. ► The catalyst shows ferromagnetic properties allowing easy separation and recovery from the liquid phase.