Hydrochar-supported CoFe ₂ O ₄ (CoFe ₂ O ₄ /HC) as heterogeneous Fenton-like catalyst: One-pot synthesis and double-active-site synergy

Ferrites have been demonstrated to be efficient heterogeneous Fenton catalysts for the removal of organic pollutants. However, pure ferrites can hardly be practically applied since magnetic ferrites are readily exposed to aggregation under ambient conditions. In this study, hydrochar-supported CoFe
2
O
4
(CoFe
2
O
4
/HC) with double active sites was prepared by one-pot hydrothermal carbonization with peanut shell, a dominant biomass waste, as the carbon precursor. The performance of the as-prepared CoFe
2
O
4
/HC in p-nitrophenol (PNP) degradation as a heterogeneous Fenton catalyst was explored, and the effects of the catalyst load, the peroxymonosulfate (PMS) concentration, and the pH on its catalytic performance were investigated. The results showed that the proposed CoFe
2
O
4
/HC can effectively and efficiently catalyze PNP degradation via PMS activation in a wide pH range (3.0∼9.0), and the optimized degradation rate was 90.85%. This can be attributed to the wide distribution of CoFe
2
O
4
on HC, which provides abundant catalytic active sites. Meanwhile, the relative contributions of different reactive oxygen species (SO
4
•-
, •OH, and O
2
•-
) were determined to be in a ratio of 6:2:3. Additionally, the catalytic performance of the as-prepared CoFe
2
O
4
/HC in real samples was consistent with that in ultrapure water, indicating high potential practical applicability of the CoFe
2
O
4
/HC. This study provides insights for high-value utilization of biomass waste and efficient removal of organic pollutants catalyzed by Fenton catalysts.