LaFeO3 and BiFeO3 perovskites as nanocatalysts for contaminant degradation in heterogeneous Fenton-like reactions

• LaFeO3 and BiFeO3 prepared and tested as catalysts for heterogeneous Fenton reaction.
• Nano-crystalline perovskites obtained by implementation of sol–gel method.
• LaFeO3 and BiFeO3 showed high catalytic activity in phenol oxidation at pH 7.
• Excellent stability of BiFeO3 in four re-use cycles.
• Mechanistic studies based on isotope fractionation experiments indicate dominant role of OH.

The present study examines the applicability of two iron-containing perovskites, LaFeO3 (LFO) and BiFeO3 (BFO), as nanocatalysts for heterogeneous Fenton-like reactions using phenol and methyl tert-butyl ether (MTBE) as model contaminants. LFO and BFO synthesized according to a sol–gel method using citric acid as complexing agent have a crystallite size of about 60–70 nm with specific surface areas of 5.2 m2 g−1 for LFO and 3.2 m2 g−1 for BFO. In heterogeneous Fenton-like reactions, LFO and BFO showed similar pseudo-first order rate constants for phenol oxidation (kLFO′=(0.13±0.01)h-1 and kBFO′=(0.15±0.01)h-1) at pH = 7 when 0.1 g L−1 catalyst and 3.0 g L−1 H2O2 were applied. Degradation efficiency was improved for both perovskites by a factor of approximately three when the pH value was slightly decreased to pH = 5. An increase of the reaction temperature from 20 °C to 60 °C during the BFO-catalyzed reaction led to a significant acceleration of phenol removal of about one order of magnitude (kBFO′=(1.9±0.1)h-1). High stability and reusability of the BFO particles was confirmed in four successive oxidation batches using MTBE as model contaminant. In addition, the mechanism of the perovskite-catalyzed Fenton-like system was studied by applying compound-specific stable isotope analysis (CSIA). The perovskite-catalyzed oxidation appears to follow a pathway similar to that of the homogeneous Fenton reaction, i.e. OH radicals play a dominant role as primary reactive species.

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