Highly efficient removal of organic contaminants based on peroxymonosulfate activation by iron phthalocyanine: mechanism and the bicarbonate ion enhancement effect

Abstract

The development of catalytic oxidation processes with high efficiency based on peroxymonosulfate (PMS) activation is a promising yet challenging research topic in the environmental catalysis field. In this work, iron tetracarboxyphthalocyanine (FeTCPc) as a homogeneous catalyst is proposed for PMS activation and construction of a novel and efficient catalytic system for the removal of Acid Orange 7 (AO7). In this system, FeTCPc exhibited extra-high catalytic activity for PMS activation, even higher than the Co²⁺ analogue of the catalyst which was identified as one of the most efficient PMS activators. A hybrid method that combines electron paramagnetic resonance (EPR) technology with different radical scavengers was employed for the investigation of active species, and the results indicate that superoxide radicals (HO₂˙/O₂˙⁻) and singlet oxygen (¹O₂) other than the sulfate radical (SO₄˙⁻) or hydroxyl radical (HO˙) were the primary reactive oxygen species during the catalytic oxidation process. Moreover, this system turned the negative effect of HCO₃⁻ observed in most reported Co²⁺/PMS systems into a positive one, which accelerated the AO7 removal with an over 10-fold increase of the rate constant due to generation of more ¹O₂. This study reports on a novel catalytic oxidation pathway for PMS activation, and paves an avenue toward developing highly efficient catalytic oxidation processes for the treatment of organic contaminants.