Predaration Of Fenton-like Catalvtic Fibers For Catalvtic Oxidation Of Dves

The Fenton reaction displays unique advantages in the treatment of organicpollutants due to its powerful oxidizing property, simplicity to control and benign reactionconditions. Nevertheless, the traditional Fenton reaction shows several drawbacks thatlimit its further application, such as narrow working pH value and causing the secondarypollution. Therefore, it is still an active and challenging research front to developpH-tolerant Fenton-like catalytic materials in the area of environmental catalysis. A novelFenton-like catalytic fibers was constructed based on the combination of the fibers’specific structural characteristics and high catalytic activity of Fenton reagents together.The catalytic activity of Fenton-like catalytic fibers was investigated with green hydrogenperoxide as oxidant and dyes as probe compounds. As compared to the use ofhomogeneous Fenton alone, the Fenton-like catalytic fibers significantly enhanced thecatalytic activity, and the catalytic reaction could proceed over a wider range of pHvalues from acidic to alkaline, indicating that it could expand the pH range effectively.This dissertation not only breaks the bottleneck that limits the widespread application ofFenton-like catalyst due to its narrow working pH value, but also endows fibers newconnotation of environmental catalysis. Importantly, it has important academic andpractical value to solve more and more serious water contamination.A novel Fenton-like catalytic fibers (FePy-CFs) was prepared by immobilizing the4-aminopyridine iron (FePy) onto cellulosic fibers (CFs) through covalent bonds. TheFePy-CFs catalytic activity was investigated, in which environmental friendly H2O2wasselected as oxidant and Rhodamine B (RhB) was used as the probe compound. Theresults revealed that more than98.2%RhB was eliminated in20min at pH2.0, and theFePy-CFs could be cycled5times without any significant loss of catalytic activity,indicating that FePy-CFs exhibited excellent catalytic activity and reusability. Ascompared to the use of FePy alone, FePy-CFs significantly enhanced the catalyticactivity (k(FePy-CFs)=0.1994min–1>>k(FePy)=0.0174min–1), demonstrating that thecellulosic fibers played an important role in the whole process including improving thecatalytic activity and avoiding the secondary pollution. Various scavengers and probe compounds (ascorbic acid, isopropanol, and dimethyl sulfoxide) combined with electronparamagnetic resonance (EPR) spectroscopy and UV-vis spectroscopy have been usedto identify the active species involved in the catalytic system. The results indicated thathydroxyl radicals (·OH), superoxide radicals (·OOH) and high-valent iron (Fe(IV)=O)may be responsible for the decoloration of RhB. On the basis of the afore analysis, apossible catalytic mechanism of the FePy-CFs/H2O2system is proposed.In order to further expand the working pH range of Fenton-like catalytic reaction, theother novel catalytic material was designed on the basis of FePy-CFs. Activated carbonfibers (ACFs) was chosen as the support due to its extremely high adsorption capacityand excellent chemical stability. We immobilized FePy covalently onto ACFs to obtainthe novel Fenton-like catalytic fibers (FePy-ACFs). The FePy-ACFs catalytic activity wasinvestigated with environmental friendly H2O2as oxidant and C. I. Acid Red1(AR1) asthe probe compound. The results revealed that more than97%of AR1could beeliminated by FePy-ACFs/H2O2in30min at pH7.0, and FePy-ACFs could be cycled5times without any significant loss of catalytic activity, indicating that FePy-ACFs exhibitedexcellent catalytic activity and reusability. Meanwhile, the FePy-ACFs/H2O2system couldefficiently oxidize various dyes, including C. I. Acid Orange II, C. I. Reactive Red M-3BE,C. I. Reactive Red X-3B, Rhodamine B, Rhodamine6G and Basic Green1. Moreover,FePy-ACFs could be cycled4times without any significant loss of catalytic activity at pH3,7,11respectively, demonstrating that FePy-ACFs possessed good chemical stabilityover a wide pH range from acidic to alkaline. As compared to the use of FePy alone,FePy-ACFs significantly enhanced the catalytic activity (k (FePy-ACFs)=0.1287min–1>>k(FePy)=0.0087min–1). This might be attributed to the fact that ACFs played animportant role in improving the catalytic activity and extending the pH range. Variousscavengers and probe compounds (isopropanol, KI, benzoquinone and dimethylsulfoxide) combined with electron paramagnetic resonance (EPR) spectroscopy andUV-vis spectroscopy have been used to identify the active species involved in thecatalytic system. The results demonstrated that hydroxyl radicals (·OH, includingthe·OH at the surface of catalyst (·OHads) and the·OH in the bulk liquid (·OHfree)),superoxide radicals (·OOH) and high-valent iron (Fe(IV)=O) may be responsible for the decoloration of AR1. Based on the analysis mentioned above, a possible catalyticmechanism in FePy-ACFs/H2O2system is proposed.