| In recent years,railway construction has developed rapidly.The train sewage system has increased the toilets on the basis of the original "straight-row" type,thus creating a new type of wastewater:toilet sewage.The toilet sewage is mainly composed of human excrement and urine.It has the characteristics of high organic matter concentration,high SS and high ammonia nitrogen,and the concentration of drug contaminants is 2?3 orders of magnitude higher than that in the sewage treatment plant and is toxic.At present,the separation and treatment of urine sources is considered to be an effective method to solve the excess of nitrogen and phosphorus in water.The high nutrients contained in urine can be used to produce fertilizers,while the drugs and nutrients in urine are used.Separation requires effective degradation of the drug in the urine,not only controlling drug contaminations from the source,but also facilitating the recovery of urine resources.In this study,two kinds of drug contaminants,sulfamethoxazole(SMX)and carbamazepine(CBZ),which are ubiquitous in human urine and poor in biodegradability,were selected for the study of photo-Fenton degradation.In this paper,iron oxychloride(FeOCl)powder was prepared by calcination pyrolysis method.The FeOCl before and after the reaction was characterized by XRD,SEM,TEM and XPS.The elemental composition and valence state were confirmed,indicating that FeOCl is a typical cuboid shape,lamellar structure,with good purity and crystallinity.At the same time,the reusability of FeOCl before and after the reaction was verified.In the ordinary water distribution test,the degradation effects of SMX and CBZ in seven systems,UV,H2O2,FeOCl,UV/FeOCl,UV/H2O2,FeOCl/H2O2 and UV/H2O2/FeOCl,were compared,indicating the degradation effect under UV/H2O2/FeOCl system is significantly better than other systems.The optimal reaction conditions for SMX and CBZ were selected based on the control of the different variables.The results showed that the optimal reaction conditions for SMX were FeOCl,H2O2 concentration of 8 mM,FeOCl powder concentration of 0.2 g/L,SMX initial concentration of 100 μM.And the optimal reaction condition for CBZ were FeOCl,H2O2 concentration of 10 mM,FeOCl powder concentration of 0.2 g/L,and CBZ initial concentration of 100 μM.The concentration of H2O2 and NH4+-N in the whole system was quantitatively analyzed under the optimal conditions.The results showed that the concentration of H2O2 remained unchanged during the reaction of the photo-Fenton system.The variation of NH4+-N concentration reflected the degradation process of SMX and CBZ and the structure of the intermediate product.The study also studied the effects of five common anions in the solution on the degradation process.The results showed that CO32-,HCO3-and Cl-inhibited the degradation of SMX and CBZ to varying degrees,and the final effect of NO3-and SO42-depends on the ion concentration.In synthetic urine test,low concentrations of SMX and CBZ showed different degradation effects in different systems.By comparing the degradation removal rate and the first-order reaction kinetic constant of SMX in fresh urine and hydrolyzed urine,the degradation effect is obtained as UV/H2O2/FeOCl>UV/H2O2>UV/FeOCl>UV>FeOCl/H2O2.The degradation rates of the four systems which with UV radiation were about 90%,and the degradation effect of each system in the two kinds of synthetic urines was not significant,showing the strong photocatalytic degradation of low concentration SMX.The degradation of CBZ in fresh urine and hydrolyzed urine is UV/H2O2/FeOCl>UV/H2O2>FeOCl/H2O2>UV/FeOCl>UV.Degradation rate and reaction rate of CBZ under UV/H2O2/FeOCl system can reach more than twice of other systems.And there is a significant difference in the degradation effect of each system in the two kinds of synthetic urines,indicating that the main effect of CBZ degradation is the·OH in the system,which indicated that the Photo-Fenton system has obvious advantages for such refractory substances. |
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