Prussian Blue Derived Heterogeneous Catalysts And Their Performance In Degrading Organic Pollutants

Fenton oxidation and peroxumonosulfate activation can degrade organic pollutants depend on highly oxidized radicals.Designing heterogeneous catalysts with high catalytic activity and stability is the key to expedite the radical production and improve the degradation efficiency of pollutants.Prussian blue?PB?and its analogues?PBAs?can not only exhibit good catalytic activity in many reactions,but also be utilized as selfsacrificing templates to prepare metal oxides and N-doped carbon,that will provide an effective approach for the synthesis of heterogeneous catalysts.In this work,different catalysts are synthesized from PB and PBAs,and the degradation efficiency of pollutants in photo-Fenton and PMS activation reactions are studied.The chloroplatinic acid with octahedral configuration can react with PB based on the outer ball reaction mechanism,and PB microcrystals with morphology evolution are preapared.BET surface area of PB hexapods?PB-hpds?is 4 times that of PB nanocubes.PB hpds presents rich FeIII-NC active sites,and 97.1 % of Rh B can be removed within 60 min.The reused PB-hpds shows higher catalytic activity than the pristine catalyst,and over 90 % of Rh B is degraded within 10 min in the tenth cycle.The increasing of FeIIINC on the surface of PB-hpds is the key factor in accelerating H₂O₂ decomposition and enhancing its photo-Fenton performance.The radical quenching and trapping tests verify that the avtive species is HO? in the system.Fe₂O₃@SnO₂nanocubes are synthesized by calcinating PB@Sn?OH?Cl nanocubes.SnO₂shells can not only preserve the microstructure of Fe₂O₃ nanocubes from hightemperature treatment,but also facilitate the phase variation from ?/?-phase to ?-phase.When Fe₂O₃@SnO₂?Sn-0.68?is employed as catalyst,Rh B degradation efficiency can reach up to 99.7 % within 60 min,and the rate constant is about 30 times that of commercial iron oxides.Various factors influencing H₂O₂ activation by Fe₂O₃@SnO₂nanocubes are discussed.When H₂O₂ concentration and catalyst dosage are 0.6 M and 0.6 g L^-1,respectively,Rh B degradation will show the highest efficiency.The radical quenching and trapping experiments show that HO? is the active species in the system.Co-Fe PBA is utilized as precursor and Sn?OH?Cl as coating to prepare Fe_xCo_3-xO₄@SnO₂nanocubes.SnO₂shells play a decisive role in stabilizing the microstructure,improving the specific surface area,enriching the octahedral-site CoII occupancy and oxygen vacancy of Fe_xCo_3-xO₄@SnO₂nanocubes.Fe_xCo_3-xO₄@SnO₂-2 presents the optimum catalytic activity,and 100 % of BPA can be removed within 40 min,which higher than that of Co₃O₄ about 40 % under the same conditions.SnO₂shells play an important role in enhibiting Co2+ leaching in the reaction.The concentration of Co2+ in Fe_xCo_3-xO₄@SnO₂-2/PMS system is 610 ?g L^-1,lower than 820 ?g L^-1 in Fe_xCo_3-xO₄/PMS system.The radical quenching and EPR examinations indicate that HO· and SO4-· are key factors in the degradation of organic pollutants.Co-Fe PBA coated with polydopamine?PDA?is utilized to prepare N-doped carbon nanocages-encapsulated carbon nanobubbles?CBs@NCCs?.The PDA-derived amorphous N-doped carbon shells play a crucial role in stabilizing the architecture and supplementing N of CBs@NCCs under high-temperature.BET surface area of PNC-800 is 412.9 m² g^-1,which are significantly higher than that of N-doped carbon derived from Co-Fe PBA.The N content of PNC-800 is 1.89 %.The PMS activation activity of CBs@NCCs is studied by degrading MB.PNC-800 shows the best catalytic performance in all samples,65.4 % of MB can be removed within 10 min and 100 % of degradation efficiency is achieved within 60 min.The radical quenching and trapping tests reveal that radical?SO₄^-·?and non-radical pathway?1O2?are responsible for the overall removal of organic contaminants.Zn-Co PBA is employed as self-sacrificing template to prepare porous N-doped carbon?PNC?microspheres.The surface N content of PNC-800 is as high as 10.5 %.PNC-800 shows the highest catalytic activity in PMS activation.It can achieve 85.0 % of MB degradation efficiency within 2 min,and almost all pollutants can be removed within 10 min.The excellent performance is attributed to its abundant porosity,high graphitization degree,and rich N substitution.Based on radical quenching and trapping experiments,a non-radical pathway is proposed to dominate organics degradation.The catalyst can adsorb PMS molecules to produce the electron transfer intermediate,which will act as a favorable platform for the direct electron transfer from organic molecules to PMS.The high graphitization degree and rich surface graphitic N are two key factors that induce the non-radical pathway.