Cu-doped Heterogeneous Fenton Catalysts And Catalytic Oxidation Mechanism

The thesis focuses on Cu-Al bonding,and the refractory organic pollutants such as Rhodamine B(RhB),2-chlorophenol(2-CP)and bisphenol A(BPA)were selected as the studied subjects.The copper-doped heterogeneous Fenton-like catalysts were prepared using simple co-precipitation and hydrothermal crystallization methods.The effects of pollutant concentration,initial pH,temperature,catalyst dosage,H2O2 dosage and Cu/Al molar ratio on pollutant degradation efficiency were investigated.The catalytic oxidation mechanism of heterogeneous Fenton catalyst in this study was revealed by many characterization techniques such as XRD,FT-IR,XPS,UV-Vis-DRs and so on.The main study contents and results are listed as follows:(1)The catalytic performance of Cu-Al2O3 heterogeneous Fenton system was investigated and the optimum reaction condition and the possible catalytic mechanism were discussed.Copper-doped aluminum oxide catalysts with a series of different copper contents were prepared using a simple co-precipitation method.The results indicated that with the Cu doped in AlPO4 increasing,the degradation rate of RhB gradually increased and up to 93.3%was removed within 4 h for Cu(4.77%)-Al2O3.In the Cu(4.77%)-Al2O3/H2O2 suspension,about 54.7% of 2-CP was degraded,meanwhile,about 50% of TOC was removed within 120 min at neutral pH.The 2-CP degradation rate within 4 h increased to 79%.The catalysts were characterized by X-ray photoelectron spectroscopy,Fourier-transform infrared spectra,electron spin resonance and X-ray diffraction.These results indicated that the synthesized heterogeneous Fenton-like catalysts with multi-valent Cu existed in the bulk framework of Al2O3 for Cu-Al2O3 with appropriate Cu doping(4.77% Cu),which exhibited high activity and long-term stability under neutral conditions.The copper species existed in the framework of Cu-Al2O3,resulting in more(·OH)generation for degradation of the refractory organic compounds.(2)Copper-doped phosphorus aluminum molecular sieve with different Cu/Al molar ratios were prepared by hydrothermal process.In the Cu(0.05)-AlPO4/H2O2 suspension,the conversion of the BPA could reach 96.31% within 150 min,and the TOC removal rate were about 22.3% and 39.9% within 3 h and 5 h,respectively.The leaching of Cu was only 0.693mg/L.In addition,Cu(0.05)-Al PO4 could be re-used and always exhibited higher activity andgreat stability.The catalysts were characterized by the studies of X-ray photoelectron spectroscopy,Fourier-transform infrared spectra electron spin resonance and X-ray diffraction.It was confirmed that the Cu species were highly dispersed in the structure or substituted the Al and P positions in the framework of the phosphorus aluminum molecular sieves.The crystal phase gradually transformed into another phosphorus aluminum molecular sieve orthorhombic crystal form with the increase of copper contents.The reactive oxygen species were detected by the ESR,indicating that H2O2 was converted into(·OH)and(HO2·/O2·).Hydroxyl radical attacked the refractory toxic contaminants and accelerated the reaction.