In a heterogeneous Fenton system, metal catalysts fixed on a solid phase surface are used instead of the traditional Fe²⁺ in Fenton reactions to activate H₂O₂ and generate hydroxyl radicals (·OH) for pollutant removal. High-valent metals at the solid-liquid interface are reduced to low-valent states by H₂O₂, enabling the recycling of the catalyst and ensuring the continuous progress of the reaction (see equations 1-3).
≡Mn+ + H2O2 → ≡M(n+1)+ +·OH + OH－ （1）
≡M(n+1)+ +H2O2 → ≡Mn+ + H2O·+ H+ （2）
H2O·+ ≡M(n+1)→ ≡Mn+ + H+ + O2 （3）
Compared to traditional Fenton reactions, heterogeneous Fenton technology significantly broadens the applicable pH range, avoids the production of iron sludge, and allows for the reuse of the catalyst.