Neutral pH Fenton and photo-Fenton activity of Mo-doped iron-pyrite particles

Abstract

Low H₂O₂ utilization efficiency for hydroxyl radical generation, acidic pH, and recyclability are critical limitations of heterogeneous Fenton and photo-Fenton catalysts. The present research shows that the optimum Mo doping of FeS₂ particles can largely alleviate these catalysis constraints. A solvothermal protocol was followed to prepare polyvinyl pyrrolidone (PVP) stabilized FeS₂ and Mo-doped FeS₂ particles. XRD observations showed that Mo doping increases the lattice parameters of FeS₂. The band gap of the Mo-doped FeS₂ particles decreased to 1.58 eV from the 2.24 eV value exhibited by pure FeS₂ particles. Structural and electronic structure DFT calculations support these results. The Fenton and photo-Fenton p-nitrophenol (PNP) degradation at neutral pH on PVP-stabilized Mo-doped FeS₂ and FeS₂ particles were examined. The photo-Fenton results were substantially better than under Fenton conditions. The best PNP degradation photo-Fenton turnover frequency (TOF) recorded was 254.50 μmol g⁻¹ min⁻¹ on the PVP stabilized 4% Mo-doped FeS₂ sample. The Mo-doped FeS₂ catalysts were stable under photo-Fenton recycling, and the H₂O₂ (1.66 mM) required for these reactions was significantly lower than most reports (30–6000 mM). Given the economic importance of the latter in Fenton/photo-Fenton reactions, H₂O₂ normalized turnover frequency (13.85 and 153.31 mg⁻¹ min⁻¹ L for Fenton and photo-Fenton) values were used to evaluate catalytic activities.