Improved Fe₂O₃/Al₂O₃ as heterogeneous Fenton catalysts for the oxidation of phenol solutions in a continuous reactor

Abstract

BACKGROUND: Improved Fe 2 O 3 /Al 2 O 3 catalysts were studied for the catalytic oxidation of concentrated phenol solutions (5 g L −1 ) with H 2 O 2 . To enhance catalyst stability, two strategies were investigated: the use of a high calcination temperature and a step of immersion into an organic acid solution. The reaction runs were performed in a continuous reactor at 70 ∘ C and atmospheric pressure. RESULTS: For all the catalysts, almost complete phenol degradation was achieved. The mineralization levels were incomplete, reaching 60 and 50% for the catalysts treated with acetic and oxalic acid, respectively. The leaching levels were reduced from 25% (for the untreated catalyst) to 11% after the immersion in oxalic acid. In all cases, the formation of reversible carbonaceous deposits was observed during reaction and a progressive decay in phenol, TOC and H 2 O 2 conversions was registered. CONCLUSION: Catalyst resistance to leaching was significantly enhanced by combining both thermal and acidic treatments. These procedures did not affect the catalytic wet hydrogen peroxide oxidation (CWHPO) performance in terms of mineralization levels. The lixiviation levels were acceptable, taking into account the strong acidic reaction medium. Deactivation processes might be primarily associated with the formation of reversible carbonaceous deposits due to intermediates accumulation onto the catalyst surface.

Catalytic wet hydrogen peroxide oxidation of p-hydroxybenzoic acid over Fe/TiO2 and 0.5Ru–3Fe/TiO2

“…In recent years, many investigators tried to improve the catalytic activity and stability of heterogeneous catalysts to enhance the efficiency of CWHPO [8]. Iron oxide appeared as a promising alternative in the CWHPO of refractory contaminant such as phenol [9,10]. Among various oxide catalysts, TiO 2 has been proved to be the most suitable catalysts for widespread environmental application because of its biological and chemical inertness, strong oxidizing power, non-toxicity and long-term stability against photoand chemical corrosion [11].…”

Preparation, characterization, and application of nano‐FeOx/Al2O3/cordierite monolithic catalysts for heterogeneous dark Fenton reaction

“…In these catalysts, the Fe(III) species are immobilized within a solid structure, and thus the reaction takes place over a wide range of pH without precipitation of iron hydroxide. The heterogeneous solid catalysts used for this purpose include iron oxides in bulk 6 or supported on carbon, [7][8][9][10] alumina, [11][12][13][14][15][16][17] or silica 18 ; pillared clays containing Fe 19,20 ; natural and artificial iron-exchanged zeolites 21,22 ; iron oxide natural minerals 23,24 ; mixed oxides 25 ; and zero-valent iron. [26][27][28] These catalysts, especially those containing Fe(III) oxides, need ultraviolet radiation to accelerate the reduction of Fe 3+ to Fe 2+ , since the reaction of Eqn (2) is much slower than the decomposition of H 2 O 2 in the presence of Fe 2+ indicated in Eqn (1).…”

“…33,[39][40][41][42][43][44][45] In the work reported here, the preparation of monolithic catalysts was proposed using commercial cordierite honeycombs as a structured substrate and alumina-supported iron oxide as active phase. This active phase was chosen because it showed good performance for degradation of organic compounds with hydrogen peroxide, [11][12][13][15][16][17] and also it meets the requirements of low cost and environmental friendliness. Some results for phenol peroxidation with iron oxides supported on various materials are presented in Table S1.…”

Removal of Phenol from Wastewater Using Fenton-Like Reaction over Iron Oxide–Modified Silicates

“…The other possibility is the immobilization on solid support. The most popular materials in this group are activated carbon, silica, and aluminum oxide [17][18][19][20][21]; however, more advanced technologies are also studied employing graphene oxide [22]. The encapsulation of iron oxide nanoparticles in polymer matrix or carbonized sewer sludge was reported as another possibility to stabilize oxide nanoparticles [23,24].…”