| Persistent organic pollutants are low water solubility,high lipotropic and hard to be degraded,they can be widely found in air,soil,water and even easily detected in human,which enables persistent organic pollutants to accumulate in humans and organisms for a long time and pose a certain threat to them.Therefore,it is the goal we have been working on to find out more emerging and more effective technologies for the rapid and efficient removal of persistent organic pollutants.So far,the remediation methods of persistent organic pollutants include physical methods(adsorption,flocculation precipitation and membrane separation),biological methods(anaerobic treatment,aerobic treatment and anaerobic-aerobic combination technique)and the advanced oxidation technologies(Fenton oxidation,ozone oxidation,photocatalytic oxidation,electrochemical oxidation,ultrasonic oxidation,etc.).In situ oxidation of persulfate is a new advanced oxidation technology based on the generation of strong oxidative species of sulfate radicals(SO4·-),which can effectively decompose persistent organic pollution.This technology has the advantages of wide application scope,strong oxidation ability and high selectivity,so it is of great significance in degrading organic pollutants.However,for some poor water-solubility persistent organic pollutants,the time for degradation is too long,and even they can't be completely degraded,so we can use some magnetic separation of catalyst and the surface modification of catalyst to change solubility of pollutants or use of the properties of the modifier to enhance the effect of degradation of pollutants.In this paper,the aim is the removal of persistent organic pollutants(BPA?4-CP),?-CD modified iron oxides were used as heterogeneous catalysts for effective degradation of persistent organic pollutants.The main contents can be summarized as follows:1.Experimental studies were conducted to investigate the degradation of bisphenol A(BPA)by using persulfate(PS)as the oxidant and Fe3O4@?-cyclodextrin(?-CD)nanocomposite as a heterogeneous activator.The catalytic degradation was evaluated in consideration of the effect of various parameters,such as pH value,PS concentration and Fe3O4@?-CD load.The results showed that 100%removal of BPA was gained at pH 3.0 with 5 mM PS,1.0 g/L Fe3O4@?-CD,and 0.1 mM BPA in 120 min.Further,the catalytic activity of Fe3O4@?-CD nanocomposite was observed as much higher when compared with Fe3O4 nanoparticles alone.The sulfate and hydroxyl radicals referred in the Fe3O4@?-CD/PS system were determined as the reactive species responsible for the degradation of BPA by radical quenching and electron spin resonance(ESR)tests.In addition,the catalyst also possessed with excellent reusability and stability.On the basis of the results of the effect of chloride ions(Cl-),?-CD was found to play a crucial role in reducing interference from Cl-ions,and lead to achieve higher removal efficiency for BPA in Fe3O4@?-CD/PS system.A possible mechanistic process of BPA degradation was proposed according to the identified intermediates by gas chromatography-mass spectroscopy(GC-MS).2.CuFe2O4@?-CD nanocomposite,synthesized by hydrothermal method combined with coprecipitation method;was employed as heterogeneous activator of persulfate(PS),and its structure was characterized by X-ray powder diffraction(XRD),Fourier transform infrared spectroscopy(FT-IR)and thermo gravimetric analysis(TGA).The results showed that the application of CuFe2O4@?-CD/PS for the degradation of chlorophenol(4-CP)is very promising.In this experiment,the effects of pH and PS concentration on the degradation of 4-CP by using CuFe2O4@?-CD were discussed,and the catalyst was found to exhibit high catalytic activity under neutral conditions.The catalytic activity between CuFe2O4@?-CD and CuFe2O4 on the degradation of 4-CP was compared.Results showed that the CuFe2O4@?-CD had more excellent catalytic activity than CuFe2O4;this may due to the existence of a ternary structure caused by ?-CD,which can increase the solubility of organic pollutants and allow free radicals more directly attack 4-CP to achieve more efficient degradation.In addition,the free radical species generated in the reaction process were determined by alcohol quenching experiment. |
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