Highly efficient LaMO3 (M = Co, Fe) perovskites catalyzed Fenton's reaction for degradation of direct blue 86.

Perovskite-structured catalysts LaMO3 (M = Co, Fe) were successfully synthesized and attempted to catalyze hydrogen peroxide (H2O2) for the degradation of Direct Blue 86 (DB86), a carcinogenic phthalocyanine dye. The heterogeneous Fenton-like reaction revealed that the oxidative power of the LaCoO3-catalyzed H2O2 (LaCoO3/H2O2) process was higher than that of LaFeO3/H2O2. When LaCoO3 was calcined at 750 °C for 5 h, 100 mg/L of DB86 could be completely degraded within 5 min via LaCoO3/H2O2 system under H2O2 0.0979 mol/L, initial pH 3.0, LaCoO3 0.4 g/L, and 25 °C. The oxidative LaCoO3/H2O2 system has a low activation energy (14.68 kJ/mol) for DB86 degradation, indicating that it is a fast reaction process with highly favorable at high reaction temperatures. For the first time, a cyclic reaction mechanism of catalytic LaCoO3/H2O2 system was proposed based on the evidence of coexisting CoII and CoIII on the LaCoO3 surface and the presence of HO• radicals (major), O2•- radicals (minor), and 1O2 (minor). LaCoO3 perovskite catalyst was reusable and still maintained reactive with a satisfactory degradation efficiency within 5 min even after five consecutive uses. This study shows that the as-prepared LaCoO3 is a highly efficient catalyst for phthalocyanine dye degradation.