| With the acceleration of the industrialization,more and more synthetic products appear in people's daily lives,resulting in a large amount of organic pollutants,many of which are directly discharged into the living water body.It causes serious ham to human body and the environment.In rencent decades,advanced oxidation technology has been widely used in the treatment of wastewater,among which high concentration refractory organic wastewater is mainly studied.In this paper,a novel type of ?-Fe2O3 sand core microspheres was prepared,and organic contaminants were degraded by strong oxidative sulfate radical(SO4-)produced by peroxymonosulfate(KHSO5,PMS)in the presence of ?-Fe2O3 with UV light.The main results are as follows:(1)An ?-Fe2O3 sand core microsphere was prepared by hydrothermal method.It was characterized via scanning electron microscope(SEM),transmission electron microscope(TEM),X-ray diffraction(XRD)and BET/BJH,and a possible formation mechanism was speculated.The results showed that ?-Fe2O3 microsphere was nearly spherical with a diameter of 50?m which was self-polymerized by ?-Fe2O3 nanoparticles with a diameter of 40 nm.The diameter of main pore was about 30 nm.Catalytic activity evaluation indicated that ?-Fe2O3 can activate PMS effectively with the assistance of UV.Acid orange 7(AO7)was almost completely degraded by the system in 40 min.Furthermore,repeatability experiments showed that ?-Fe2O3 has fairly good stability,and the degradation rate of AO7 reached about 80%after the 10th cycle.(2)AO7 was selected as a simulated dyeing wastewater,and a possible reaction routes of UV/?-Fe2O3/PMS was speculated via V-vis spectroscopy and ESR technology.The results indicated that electrons(eCB-)in the surface of ?-Fe2O3 could be excited by UV and leave holes(hVB+)in situ.While PMS,an electron trapping agent,not only effectively inhibit the recombination of eCB-and hVB+,but also break the-O-O-bond quickly to produce SO4-·,while SO4-· will further react with H2O or OH-to generate ·OH,and AO7 molecule was oxidative degraded by SO4-· and ·OH.Furthermore,the influence factors of the UV/?-Fe2O3/PMS system were investigated,the results showed that the degradation of AO7 was positively correlated with the concentration of PMS.With the increase of ?-Fe2O3 dosage,the degradation rate of AO7 showed a trend of increasing first and then decreasing.Strongly acidity and alkaline enviroment will reduce the degradation rate of AO7.Inorganic anions can promote the degradation of AO7 to a certain extent,among which CO32-exhibit significant promotion performance with nearly 100%degradation of AO7 after 30 min reaction.The fitting results of the degradation at different initial concentrations of AO7 indicated that the system were in accordance with pseudo-first-order kinetics and the linear correlation coefficient R2=0.8759?0.9623 and the reaction rate constant decreases from 0.1633 min-1 to 0.0237 min-1 with the initial concentration of AO7.(3)Distribution and transformation of dissolved organic matter(DOM)in landfill leachate were investigated.Optimal experimental conditions(the dosage of ?-Fe2O3 is 2.0 g/L,the dosage of PMS is 8.0 g/L,and the pH is 5.0)were obtained through orthogonal experiment.The contribution of conditions were ranked as:PMS dosage>?-Fe2O3 dosage>pH value.After 60 min reaction,72.4%of DOM was removed among which humus substances removed 92.4%through 3D-EEM;GPC analysis indicated that organic contaminants with molecular weight range>1500 Da reduced significantly while molecular weight range 500-1500 Da increased.It indicated that macromolecular weight dissolved organic matter was converted into small-molecule organic matter or mineralized.Organic contaminants were degraded via oxidation bond breaking and electron transfer by SO4-·.GC-MS analysis showed that after reaction,macromolecules in landfill leachate contaminants decomposed effectively by SO4-·.The aromatic phenols and alkanes could be effectively removed,and alcohols and esters and other intermediate products were produced. |
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