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 environ- mental 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 solu- tion 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 hy- drogen 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; H2O2: 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/H2O2 catalytic system exhibited remark- able catalytic activity across a wider pH range (2~10) and the values of apparent rate constant (kapp) were greater than 0.320 min −1 , which was efficient to expand the pH range for the traditional Fenton reaction. Various scavengers and probe com- pounds (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 radi- cal (HO2•) may be responsible for the degradation of dyes. This paper discusses a possible catalytic oxidation mechanism in the Cit-Fe@ACFs/H2O2 system, which may be a feasible approach for the elimination of widely existing pollutants. Keywords activated carbon fibers; ferric citrate; Fenton-like; catalytic fibers; dyes