Iron phthalocyanine doped carbon-based as a bifunctional material for peroxymonosulfate activation toward Reactive Red 24 degradation: Consolidated adsorption and multiple oxidation

Abstract

The industrial wastewater containing some refractory macromolecule active dyes is usually hard to be treated effectively through the traditional physio-chemical and biological methods. In this study, an innovative non-homogeneous catalyst system with efficacious oxidation capacity, namely iron phthalocyanine (FePc)-doped millet biochar (mBC) with the function of activating peroxymonosulfate (PMS), was constructed for the degradation of reactive red 24 (RR24). The obtained FePc-mBC exhibited an efficient adsorption with a catalysis performance of a 93 %-removal efficiency for RR24 in 120 min, and meanwhile this novel catalyst performed remarkable adaptability at the wide pH range from 3 to 10. The FePc-introduced significantly weakened the boundary layer thickness of the material to absorb RR24 uniformly under acidic conditions, which creating a favorable condition for subsequent efficient oxidation. Both free radicals and non-free radicals were involved in the oxidation reaction of which, the constructed N(C)-O- acted as the axial ligand to bridge with Fe in FePc and induced -O-O- heterolysis to produce Fe (IV) = O, which was identified as the effective precursor product of 1O2, the main player for the RR24 oxidation reaction. Besides, the FePc prompted the formation of persistent free radicals (PFRs) on the mBC, as a single-electron body, which induced the redox cycling of Fe (III) and Fe (II) and maintained the “continuity” capacity of the system. Overall, this work provides a new insight into the development of bifunctional metal complex/biochar composites and creates a reasonable system containing diversified and multi-functional active species for the oxidation of refractory organic pollutants.