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Abstract: 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 4h under stoichiometric H2O2 dose, 100mgL−1 initial chlorophenol concentration, 1gL−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 100h 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. [Copyright &y& Elsevier]

Abstract: Degradation of chlorophenols by a sequential combination of hydrodechlorination (HDC) and catalytic wet peroxide oxidation (CWPO) using a new magnetic Pd–Fe/γ-Al2O3 catalyst has been studied. This catalyst is active in both hydrodechlorination of chlorophenols and decomposition of H2O2 for the oxidation of organic compounds. The sequential combination of HDC and CWPO allows overcoming some of the drawbacks of both treatments applied independently. The HDC step achieves the complete dechlorination of chlorophenols, so that the subsequent CWPO does not lead to the formation of highly toxic chlorinated by-products and reduces significantly the organic load of the effluent. The results showed that the presence of iron in the Pd catalyst improved significantly its hydrodechlorination rate, achieving the complete dechlorination of chlorophenols in a short reaction time (≈15 min), giving rise to phenol and cyclohexanone. The CWPO of synthetic mixtures of phenol and cyclohexanone showed that a high phenol concentration promotes the oxidation of all the organic species, but the presence of cyclohexanone seems to hinder the formation of aromatic radicals limiting the effectiveness of the CWPO step. Therefore, the effective combination of HDC and CWPO requires that the HDC step achieves the complete dechlorination of chlorophenols but no further hydrogenation is needed. The Pd–Fe/γ-Al2O3 catalyst showed a high activity in both HDC and subsequent CWPO of chlorophenols being easily separated and recovered from the reaction medium due to its ferromagnetic properties. In spite of a moderate loss of activity, the complete dechlorination of chlorophenol and a negligible ecotoxicity of the final effluents were maintained upon successive applications of HDC + CWPO in a four-cycles test. [Copyright &y& Elsevier]