Study On PMS Activating Carbon-based Materials And Their Organic Pollutants Degradation Performance

Advanced oxidation processes using peroxymonosulfate(PMS)as oxidant to degrade organics in water is superior to conventional Fenton method,which has attracted extensive attention in recent years.Generally,powder catalysts containing transition metal are used to catalytically activate PMS.However,these catalysts are difficult to be recovered,and leaching of metal may cause secondary pollution.Aiming at aforementioned drawbacks,two novel carbon-based catalysts were prepared.The performance and mechanism of PMS activation and pollutant degradation by these catalysts were investigated,which may provide new ideas for synthesis and application of catalysts.Main contents are as follows:(1)Monolithic cobalt-containing carbon aerogel catalyst was gained by carbonization and air thermal treatment of organogel precursor fabricated by co-condensation of cobalt ions,graphene oxide sheets and resorcinolformaldehyde resin.Thermal treatment in air could improve its hydrophilicity,porous structure(BET specific surface area was 671 m2 g-1)and stability of active sites.The monolithic catalyst(1 g L-1)contained a low amount of cobalt(0.066 wt%),and could achieve a high phenol(20 mg L-1)degradation efficiency of 86.7% in 60 minutes with a low amount of cobalt leaching and apparent activation energy(38.2 k J mol-1).It could be removed from the reaction system completely without difficulty.PMS was activated mainly through a radical path.(2)Polypyrroles,prepared through chemical oxidative polymerization using ammonium persulfate and ferric chloride,respectively,were carbonized at different temperatures to synthesize nitrogen-doped carbonbased catalysts.Graphitization extent and order of the carbon base,amount of nitrogen doping(especially graphitic nitrogen),and specific surface area integratedly determine the catalytic activity of the catalysts.Among the catalysts,the product prepared by ferric chloride and carbonized at 800 °C possessed the best catalytic performance.It(0.2 g L-1)could completely degrade phenol(20 mg L-1)and achieve a total organic carbon removal efficiency of above 94% in 40 minutes with a low apparent activation energy(18.4 k J mol-1).The nitrogen-doped carbon-based catalysts could degrade phenol efficiently in a wide p H range(2–9).(3)The nitrogen-doped carbon-based catalysts activated PMS through a non-radical path,which could degrade organic pollutants selectively.The organics with electron-donating groups on the benzene ring could be degraded more easily.The carbon-based catalysts would be oxidized and deactivated directly by PMS,and could be recovered by thermal treatment.