Biochar-regulated LDH-derived Co–Mn spinel for non-radical peroxymonosulfate activation: high-efficiency imidacloprid degradation dominated by high-valent metal–oxo species and singlet oxygen

Abstract

Neonicotinoid insecticides (NNIs), notably imidacloprid (IMI), are widely detected in aquatic ecosystems, presenting substantial ecological threats due to their persistence and detrimental effects on non-target organisms. Current remediation strategies are frequently constrained by inefficiencies or excessive energy consumption. Here, we engineered a suite of cobalt–manganese spinel/biochar composites (CoMn_x/BC) through the controlled calcination of CoMn-layered double hydroxide intercalated with BC. The optimized CoMn_0.75/BC composite demonstrated exceptional efficacy in activating peroxymonosulfate (PMS), achieving a 96.9% removal of 5 mg L⁻¹ IMI within 40 min and a degradation rate constant of 0.209 min⁻¹. Mechanistic investigations unveiled that while CoMn₂O₄ primarily activates PMS via radical pathways involving hydroxyl radicals (·OH), the CoMn_x/BC composites shift the activation mechanism towards non-radical routes, dominated by high-valent metal–oxo species and singlet oxygen (¹O₂). Our findings elucidate the pivotal synergistic role of BC in modulating both the structural attributes and catalytic mechanisms of spinel-based composites. These insights offer a rational design blueprint for advanced BC-hybrid catalysts tailored for the efficient treatment of high-strength industrial wastewater contaminated with NNIs.

Graphical Abstract

Keywords

Biochar / PMS activation / High-valent metal–oxo species / Singlet oxygen / Imidacloprid

Highlight

•	CoMn0.75/BC degrades 96.9% of imidacloprid in 40 min.
•	Biochar triggers a radical-to-non-radical shift in PMS activation, dominated by high-valent metal–oxo species and 1O2.
•	Biochar’s surface C=O groups chelate Co/Mn ions to stabilize high-valent metal–oxo species.
•	Biochar-bounded PFRs mediate PMS via non-radical pathways to promote 1O2 generation.
•	Biochar endows the composite with high stability and anti-interference in real water matrices.

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Funding

National Natural Science Foundation of China(52479037)

Distinguished Youth Science Foundation of Heilongjiang Province, China(JQ2023E001)

Young Leading Talents Project of Northeast Agricultural University, China(NEAU2023QNLJ-013)

RIGHTS & PERMISSIONS

The Author(s)