Hydrothermally treated peat/magnetite composites as highly efficient heterogeneous Fenton catalyst: Integrating multiple reaction mechanisms to enhance the catalytic reactivity for BPA removal

Although various strategies have been developed to boost the reactivity of heterogeneous Fenton catalysts, integrating multiple strategies in one catalyst to achieve high Fenton reactivity is still a challenge. To tackle this issue, the ball-milled peat and magnetite (Mag) composites were hydrothermally treated to synthesize novel heterogeneous Fenton catalyst (i.e., Mag-HTP) for bisphenol A (BPA) removal. The degradation efficiency of BPA (30 mg/L) by H2O2 (2 mmol/L) activated with 50 %Mag-HTP (0.2 g/L) was above 98% within 120 min at initial pH 3. The calculated degradation rate constant of Mag-HTP was 0.0873, which was 20.6 folds higher than that of Mag; moreover, it possessed high reactivity over a wide pH range (3–7) with low H2O2 dosage (0.5–2 mM), and high reaction stability (eight cycles with degradation rate over 95%). The multiple reactive mechanisms were validated: (1) NMR/XPS spectra, H2O2 decomposition, and HO production experiments proved the HTP as an electron donor could directly reduce Fe(III); (2) C-V curves proved the formed C-O-Fe bonds could lower the Fe(II)/Fe(III) redox potential; (3) Raman/EIS spectra, Tafel plot, and radical scavenging tests proved that HTP could serve as an electron shuttle for transferring electrons from H2O2 to Fe(III); (4) NMR spectra proved the formed C-O-C bonds on HTP could function as the dual-reaction-center in Fenton reaction. These multiple mechanisms collectively contributed to the high reactivity of Mag-HTP in the Fenton reaction. Therefore, Mag-HTP shows great potential for practical applications in wastewater treatment and soil remediation due to its cost-effectiveness, easy separation, and high Fenton reactivity.