Activation Of Peroxymonosulfate By Carbon-based Material For The Degradation Of Organic Pollutants

With the improvement of industry production and the development of people's living standards,the environmental problems caused by water pollution have become increasingly serious.Organic pollutants such as dyes and phenols in printing and dyeing wastewater have become potential killers of the environment and human health,which not only hinder the metabolism of aquatic organisms,but also have obvious carcinogenicity to the human body.Therefore,how to quickly and efficiently remove organic pollutants from wastewater has become one of the important topics for researchers.Advanced oxidation based on sulfate radical(SO₄^-?)is a water treatment technology that produces SO₄^-?by activation of peroxymonosulfate?PMS?.It has the advantages of strong oxidation,wide pH range,long life of free radicals and good mineralization.The traditional transition metal activated PMS to produce SO₄^-?also has higher efficiency,but it has limited its wider application due to the dissolution of metal ions.In recent years,carbon materials as heterogeneous catalysts have attracted interest due to their no metal ion leaching,low cost,high reactivity and simple process.The high-efficiency activation properties of the transition metal can be retained by complexing with the carbon material,which not only effectively protects the metal from corrosion and leaching in the aqueous solution,but also exposes more active sites.In addition,nitrogen doping in carbon materials can effectively improve the surface activity and electron conduction properties of the carbon material.Therefore,nitrogen-doped carbon materials have a good application prospect.In this paper,the carbon material carbon materials are used as carriers.Fe@HC,FeCo2O4,Fe-N-C and FeCo-N-C nanocomposite were synthesized to activate PMS to degrade organic pollutants.The contents are mainly divided into four aspects:?1?A hydrothermal iron carbon catalyst was prepared by hydrothermal treatment of a mixture of lignin and ferric nitrate?Fe@HC?.The performance of different catalysts used to activate PMS for phenol degradation was tested at room temperature.Experiments show that Fe@HC-800 exhibits high catalytic activity.Further catalytic experiment revealed that phenol could be completely degraded by Fe@HC-800 within 20 min.The degradation rate of phenol on Fe@HC-800 catalyst was 0.3800 min^-1.A series of characterization such as XPS,SEM,EDS,TEM were used to characterize the structure of catalyst.The effects of reaction temperature and PMS dosage on the catalytic performance were investigated.The XPS and XRD results proved the key role of Fe⁰ in the degradation of phenol.?2?Fe-Co-ZIF nanocage was prepared by using ZIF-67 as template,and then calcined at high temperature to obtain FeCo₂O₄-N-C nanocomposite to activate PMS to degrade methylene blue?MB?.The structure of the catalyst was characterized by XRD,SEM,TEM,FT-IR and XPS.The effects of reaction temperature,MB concentration,catalyst dosage and PMS dosage on the degradation process were investigated.Experiments show that the degradation rate of 50 ppm MB by FeCo₂O₄-N-C-400 is up to 100%.The free radical quenching experiments of methanol and tert-butanol revealed the contribution of SO₄^-?and·OH in the degradation of MB by FeCo2O4-N-C-400/PMS system.The stability of the catalyst was tested by repeated experiments,indicating that FeCo2O4-N-C-400 had good catalytic performance and stability.?3?Nitrogen-doped porous carbon encapsulating iron nanoparticles?Fe-N-C?was fabricated by a simple and environmentally-friendly method using waste biomass,urea and potassium ferrate?K₂FeO₄?as the C,N and Fe precursors.Phenol was then used to assess the adsorption and catalytic activity of Fe-N-C catalyst with peroxymonosulfate?PMS?as an oxidant.The effects of reaction parameters on phenol degradation,such as PMS concentration and reaction temperature on oxidation as well as the stability of the composite were extensively evaluated.Results from XPS characterization were used to illustrate that graphitic N and a certain amount of iron on the Fe-N-C surface acted as the active sites.Kinetic study showed that the first-order kinetic reaction followed by the degradation of phenol by Fe-N-C catalyst produced a lower activation energy,which was 17.21 kJ?mol^-1.Electron paramagnetic resonance?EPR?studies and quenching tests revealed the important contribution of sulfate radicals(SO₄^-?)and hydroxyl radicals?·OH?during the degradation of phenol.The stability of the catalyst was tested by repeated experiments,indicating that Fe-N-C had good catalytic performance and stability.?4?g-C₃N₄ and MOF?2Fe/Co?were used as raw materials to prepare a heterogeneous activated PMS with 20 nm FeCo alloy nanoparticles loaded with nitrogen-doped carbon support?FeCo-N-C?by direct pyrolysis catalyst.The catalyst displayed outstanding activity and stability for peroxymonosulfate?PMS?activation,resulting in the fast generation of sulfate(SO₄^-?)and hydroxyl?·OH?radicals which then quickly oxidized aqueous rhodamine B(RhB,60 mg?L^-1 was degraded in 5 min).EPR and radical trapping experiments allowed the excellent catalytic performance of the FeCo-N-C/PMS system to be understood and plausible reaction mechanisms developed.The graphite-N on the FeCo-N-C catalyst was the active site of PMS activation,which promoted the adsorption and dissociation of PMS by activating adjacent carbon atoms.The results confirmed that the synergistic effect of N doping sites and FeCo nanoparticles in FeCo-N-C catalyst enhanced the degradation of RhB.