Particulate matter capturing over manganese dioxides with different crystal structures

Particulate matter(PM)is the main contributor to air pollution,and filtration has been reported to be promising for PM capturing.Considering the complexity of polluted air(volatile organic compounds(VOCs)and ozone are likely concomitant with PM particles)and in view of the versatility of MnO_(2) for the degradation of VOCs and ozone,the feasibility of MnO_(2) materials as PM filteringmediawas investigated in this study,and the effect of crystal structure on PM filtration was clarified.Compared with the layeredδ-MnO_(2),the MnO_(2) with tunnel structure(including 1×2-,2×2-and 3×3-MnO_(2))exhibited greatly enhanced PM removal efficiencies,and particularly,the 3×3-MnO_(2) possessed not only significant activity for adsorbing PM particles but also high utilization efficiency of the active surface.Physicochemical properties of the adsorbents were studied by XRD,ATR,isothermal N_(2) adsorption,SEM and(HR)TEM.The correlation between pore characteristics and particle elimination activity demonstrates that the most developed mesoporous structure of the 3×3-MnO_(2) sample played an important role in strengthening the PM adsorption capability.Further comparison of the surface properties of the fresh and spent samples reveals that with respective to the occasion ofδ-MnO_(2),the structure of 3×3-MnO_(2) was robust enough to resist collapse after PM capturing and the great accommodation of the inorganic and organic PM substances in the voluminous pores induced strong affinity between PM particles and 3×3-MnO_(2).Thereby,a higher particle filtration ability was retained.

Identification and characterization of Fe_(3)O_(4)/peroxodisulfate advanced oxidation products from sulfameter

Sulfonamides(SAs)are one of the most widely used antibiotics and their residuals in the environment could cause some negative environmental issues.Advanced oxidation such as Fenton-like reaction has been widely applied in the treatment of SAs polluted water.Degradation rates of 95%-99.7%were achieved in this work for the tested 8 SAs,including sulfisomidine,sulfameter(SME),phthalylsulfathiazole,sulfamethoxypyridazine,sulfamonomethoxine,sulfisoxazole,sulfachloropyridazine,and sulfadimethoxine,in the Fe_(3)O_(4)/peroxodisulfate(PDS)oxidation system after the optimization of PDS concentration and p H.Meanwhile,it was found that a lot of unknown oxidation products were formed,which brought up the uncertainty of health risks to the environment,and the identification of these unknown products was critical.Therefore,SME was selected as the model compound,from which the oxidation products were never elucidated,to identify these intermediates/products.With liquid chromatography-high resolution tandem mass spectrometry(LC-HRMS/MS),10 new products were identified,in which 2-amino-5-methoxypyrimidine(AMP)was confirmed by its standard.The investigation of the oxidation process of SME indicated that most of the products were not stable and the degradation pathways were very complicated as multiple reactions,such as oxidation of the amino group,SO_(2)extrusion,and potential cross-reaction occurred simultaneously.Though most of the products were not verified due to the lack of standards,our results could be helpful in the evaluation of the treatment performance of SAs containing wastewater.