Pyrrolic N and persistent free radical synergistically promote catalytic degradation of dyes via Fe2O3/activated biochar derived from Taihu blue algae

Abstract

Fe-based activated biochar composites are promising catalysts for environmental remediation. However, the limited efficiency of Fe(III)/Fe(II) cycling reaction of commercial Fe2O3 at neutral conditions still impeded the catalytic performance of the heterogeneous Fenton-like catalysts. In this work, high-performance Fe2O3/activated biochar Fenton-like catalysts with Taihu blue algae (hazardous algae to aquatic ecosystems) as carbon precursors were synthesized and used for the degradation of methylene blue (MB). The physicochemical properties of Fe2O3/activated biochar composites including pore structure, the generated N species, and persistent free radicals (PFRs) were effectively tailored by activation temperatures. ACK-7-Fe (prepared under the activation temperature, 700 °C) showed a stronger adsorption ability while ACK-8-Fe (800 °C) exhibited superior MB degradation performance (∼99.97% in 30 min at neutral pH). The former was ascribed to the formation of more mesopores with suitable size which was beneficial for MB adsorption. The latter is due to the promoting effect of pyrrolic N and PFRs on the Fe(III)/Fe(II) cycle, responsible for the high catalytic efficiency of ACK-8-Fe. The hydroxyl radicals were the dominant active radicals evidenced by scavenging experiments and electron spin resonance. Moreover, the. The ACK-8-Fe exhibited superior reusability, which was crucial for its practical applications.