Degradation Of Organic Pollutants In Water By Persulfate With The Assistance Of Solar

Recently,advanced oxidation techniques based on persulfate（PS）have been applied to treat refractory organic pollutants in water.Because of its wide p H application,strong oxidation ability and high selectivity to drugs,it has a broad application prospect in sewage treatment.How to activate PS quickly and efficiently is the key to this technology.There are many ways to activate PS,such as photoactivation,thermal activation,alkali activation,transition metal activation,etc.Among them,photoactivation is widely studied because of its green environmental protection and low cost.Firstly,the degradation properties of ofloxacin（OFX）by solar PS system were studied,then ferrous oxalate and bismuth tungstate were prepared by co-precipitation method,the photocatalytic activation properties of persulfate were studied,and the degradation mechanism of pollutants was explored.The main contents of the study can be summarized as follows:（1）This chapter studies the effects of water quality conditions on the degradation of OFX by solar/PS systems,and discussed the degradation mechanism of OFX.It turns out,the combination of PS and sunlight has a significant synergistic effect on OFX degradation.The degradation curve can be fitted well with the pseudo first order model.As the solution p H increases from 4 to 10,the reaction rate constant rises from 0.0909 to 0.9704 min^-1.The degradation rate constant at p H4-8(0.6916–0.9704 min^-1)is much higher than many reported PS activation systems.In addition,the common inorganic ions in water have little effect on OFX degradation,indicating that this process has practical application prospects.Studies have shown that PS is barely activated by sunlight and the free radicals are very limited,so the degradation of OFX does not follow the free radical mechanism.OFX is more easily activated by solar irradiation than PS.Although PS is difficult to react with OFX,it can easily oxidize OFX activated by light.Therefore,the combination of PS and sunlight can effectively degrade OFX.（2）This chapter uses a simple coprecipitation method,FeC₂O₄ were successfully prepared from ferrous sulfate（Fe SO₄·7H₂O）and oxalic acid（H₂C₂O₄·2H₂O）as raw materials through its activation PS the successful degradation of the phenolic pollutant p-nitrophenol（PNP）,and compared its photocatalytic performance.It turns out,the degradation rate of PNP by solar/FeC₂O₄ system is only 54%,and the degradation rate of the solar/PS/FeC₂O₄ system was83%respectively.Through exploring the effects of PS concentration,catalyst dosage and initial p H,the optimal reaction conditions were found,and it was found that when the PS concentration is 1.5 mmol·L^-1、the FeC₂O₄ concentration is 0.1 g·L^-1、and p H3 is the optimal reaction condition.The effects of common ions in water on the reaction were further explored.The main active species for degradation PNP were identified by trapping agent experiments and electron paramagnetic resonance spectroscopy（EPR）as hydroxyl radicals（·OH）and sulfate radicals（·SO₄^-）.Eventually,by liquid chromatography-mass spectrometry（HPLC-MS）,and proposed a possible PNP degradation pathway.（3）Bismuth tungstate（Bi₂WO₆）has been successfully prepared by hydrothermal method in this chapter.Through its photocatalytic activation PS cefalexin（CPX）.The effects of different PS concentration,catalyst dosage,initial p H、pollutant concentration,light intensity,common ions in water and different light sources on the reaction conditions were investigated to determine the optimal reaction conditions.It turns out,Bi₂WO₆ is an effective catalyst that can effectively activate the PS degradation and mineralization CPX under sunlight irradiation,it is the best reaction condition when the PS concentration is 1.5 mmol·L^-1、Bi₂WO₆ the concentration is 1.5 g·L^-1and p H6.Further,the capture agent experiment shows that the degradation of CPX is the result of the interaction of many active species.