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

Abstract

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 60–70nm with specific surface areas of 5.2m2g−1 for LFO and 3.2m2g−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 0.1gL−1 catalyst and 3.0gL−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.