Activation of Hydrogen Peroxide by Activated Carbon Fibers Coupled with Fe(Ⅲ)-Citrate for Degradation of Dyes at Neutral pH

The development of a pH-tolerant Fenton-like catalyst is a active and challenging project in the field of environmental catalysis.In this work, an efficient Fenton-like catalytic fibers (Cit-Fe@ACFs) with pH-tolerance has been prepared by an extremely simple impregnation method.First, activated carbon fibers (ACFs) were impregnated into a nitric acid solution at 25 ℃ for 24 h to obtain acidified ACFs, and then immersed in a sodium citrate solution at 25 ℃ for 2 h, which was taken out to put into ferric chloride solution at 25 ℃ for 2 h.The treated ACFs were rinsed with distilled water and dried at room temperature to obtain the Cit-Fe@ACFs.Cit-Fe@ACFs exhibited efficient catalytic activity for the activation of hydrogen peroxide at neutral pH to degrade dyes, including reactive, acid, and basic dyes, etc.The UV-vis spectroscopy showed that reactive brilliant red M-3BE (RR M-3BE) was eliminated completely in 15 min (Cit-Fe@ACFs: 12 g/L; H 2 O 2 : 60 mmol/L; RR M-3BE: 5×10 -5 mol/L; pH 7; T＝50 ℃).Moreover, the catalyst presented excellent regeneration capability and sustained catalytic ability in these experiments.Importantly, the Cit-Fe@ACFs/H 2 O 2 catalytic system exhibited remarkable catalytic activity across a wider pH range (2～10) and the values of apparent rate constant (k app ) were greater than 0.320 min -1 , which was efficient to expand the pH range for the traditional Fenton reaction.Various scavengers and probe compounds (n-butanol, benzoquinone) combined with electron paramagnetic resonance (EPR) spectroscopy were used to identify the active species involved in the catalytic system.The results revealed that the hydroxyl radicals (•OH) and superoxide radical (HO 2 •) may be responsible for the degradation of dyes.This paper discusses a possible catalytic oxidation mechanism in the Cit-Fe@ACFs/H 2 O 2 system, which may be a feasible approach for the elimination of widely existing pollutants.