Characteristics of Fe/C catalysts based on pyrolysis of ferric citrate and its peroxymonosulfate activation performance to degrade sulfadiazine in water

Abstract

Advanced oxidation techniques based on peroxysulfate activation have been paid much attention owing to their excellent performance in degrading stubborn pollutants in water. In response to the current situation that requires more raw materials and higher costs and involves more complicated processes for the preparation of Fe/C catalysts to activate persulfates, novel catalysts (Fe/C-700, Fe/C-800, Fe/C-900 and Fe/C-1000) were prepared by a high-temperature carbonization method at different pyrolysis temperatures (700, 800, 900 and 1000 °C) using inexpensive and environmentally friendly ferric citrate as raw material. Fe/C catalysts were characterized using SEM, EDS, XRD, XPS, and VSM and were screened for the activation of peroxymonosulfate (PMS) to degrade sulfadiazine (SDZ) in water, where Fe/C-900 exhibited higher efficiency. Thus, its activation performance for PMS to degrade SDZ was comprehensively investigated and the mechanisms of activation degradation were analyzed. The results showed that the degradation rate of 98.7% can be achieved to 10 mg L⁻¹ SDZ by 0.1 g L⁻¹ Fe/C-900 and 0.5 mmol L⁻¹ PMS within 60 min. A wide range of solution pH, low catalyst dosage and good recycling performance were found in the Fe/C-900 application and the amount of iron ions dissolved at the end of the reaction was low (0.350 mg L⁻¹). It was shown that both free radical and non-free radical pathways existed in the reaction system, where ¹O₂, SO₄⁻˙ and O₂⁻˙ played dominant roles in the degradation process of SDZ. The results could provide new ideas for the preparation of Fe/C catalysts and their heterogeneous activation for PMS to degrade stubborn organic pollutants in water.