Study On Metal Organic Framework-Based Fenton-Like Catalyst For Active Pharmaceuticals Degradation In Aqueous Solution

In recent years,anti-inflammatory pharmaceuticals and antibiotics,as typical representatives of active pharmaceutical pollutants,are widely present in urban sewage treatment plants,hospital sewage,surface water,and even drinking water systems,posing potential risks to human health and the environment.In order to eliminate the impact of active pharmaceuticals on ecosystems and human health,research efforts have focused on developing effective technologies to remove active pharmaceuticals from the aquatic environment.Currently,the Fenton-like technology of solar assisted or persulfate(PMS)activation has attracted extensive attention from researchers.Metal organic frameworks(MOFs)have been widely used in various catalytic reactions due to their high porosity,adjustable active centers,and ease of functional modification,becoming the focus of concern.However,MOFs materials generally have the disadvantage of poor electrical conductivity,which is not conducive to the rapid transfer of electrons,thereby affecting the efficient removal of active pharmaceutical pollutants.In order to solve the above problems,this thesis aims to achieve efficient and stable removal of active pharmaceutical pollutants in the Fenton-like process by preparing MOFs composite materials and MOFs derived materials,while leveraging the structural advantages of MOFs materials while improving their ability to resist external influences.The main research contents and achievements are as follows:(1)Aiming at the degradation problem of acetaminophen(APAP),a representative of nonsteroidal pharmaceuticals in anti-inflammatory pharmaceuticals,CuS modified MIL101(Fe)(CuS/MIL-Fe)heterojunction catalysts were designed to activate hydrogen peroxide(H2O2)under simulated light conditions to achieve APAP highly efficient removal.The experimental results showed that the degradation rate of 5 mg/L APAP was 0.210 min-1 at 0.2 g/L CuS/MIL-Fe and 15 mM H2O2,which was elevated nearly 6-fold compared with MIL-101(Fe)alone,and showed good catalytic performance at pH=3-7.The characterization and theoretical calculation proved that CuS/MIL-Fe catalyst could improve the separation and transfer efficiency of photo-generated hole electrons through close contact interface,and CuS acted as an electron donor to promote the regeneration of active site Fe2+ and finally realized the synergism of light and Fenton degradation reaction.In addition,the sites at which APAP could be easily attacked by reactive oxygen species were predicted by multiwfn software,while the ecological toxicity assessment of APAP and its intermediates was carried out by employing toxicity assessment software(ECOSAR)based on quantitative structure-activity relationship(QSAR)model.(2)Aiming at the degradation problem of sulfamethazine(SMT),a representative of sulfonamides in antibiotics,Co9S8 catalysts with rich sulfur vacancies were prepared by means of solvothermal and high-temperature treatment using ZIF-67 of cobalt-based MOFs as precursors.PMS-based Fenton-like technique was adopted to solve the problems in photo-Fenton technology,which were relatively narrow application range of pH and relatively high usage of oxidants.The results showed that sulfur vacancies could modulate the electronic structure of active site Co to affect the adsorption and activation process of PMS,including improving the adsorption capacity to PMS and reducing the barrier of OO bond cleavage during PMS activation.Finally,under the conditions of 0.15 g/L catalyst and 0.6 mM PMS,the degradation rate of 10 mg/L SMT by Co9S8 catalyst rich in sulfur vacancies was 0.631 min-1,which was 42 times higher than that of Co9S8 catalyst without sulfur vacancies,and showed good catalytic performance at pH=5-11.Moreover,based on experimental analysis,theoretical calculations and QSAR analysis,the degradation pathway and the ecotoxicity assessment of SMT and its intermediates were proposed.(3)In order to further improve the catalyst activity and reduce secondary pollution,cobalt sulfide/graphite carbon nitride composite(CoS/CN)was prepared by solvothermal methods using ZIF-67/graphite carbon nitride as the precursor for the sulfonamide(SA)degradation.The results showed that g-C3N4 can not only improve the dispersion of CoS,but also adjust the electronic density distribution of catalyst to promote the electronic transfer between the catalyst and PMS and improve the degradation rate of SA.Under the conditions of 0.10 g/L catalyst and 0.4 mM PMS,the removal efficiency of 10 mg/L SA by CoS/CN is more than 95%within 2 min,and the degradation rate is up to 2.490 min-1.During the degradation process,the synergism of singlet oxygen(1O2)and sulfate radical(SO4·-)makes the system have high mineralization rate.The degradation pathways of SA were analyzed by liquid chromatography-mass spectrometry,theoretical calculation and QSAR,and the toxicity of intermediate products was given.(4)In order to further improve the stability of the catalyst,CoS2/MoS2 with core-shell structure was synthesized by using ZIF-67 as the precursor.The comprehensive performance of CoS2/MoS2 activatied PMS to degrade SMT was evaluated,and the advantages of special structure were explored.The results showed that CoS2/MoS2 catalyst had a close contact interface,which could regulate the electron density of the Co 3d orbital to promote the adsorption and the activation of PMS at the interface.Meanwhile,the MoS2 as the shell had a certain adsorption effect on pollutants,which could concentrate the degradation process in a confined space.This structural advantage could achieve complete removal of SMT and removal of more than 60%of total organic carbon within 15 min.In a fixed bed reactor,CoS2/MoS2 catalyst was fixed on the polyester fiber ball carrier,and the treatment performance of the system is stable under the continuous flow mode.After 12 hours,it could still reach more than 90%of SMT degradation,indicating that the shellcoating strategy was an effective strategy to improve the stability of the catalyst.In summary,this study has developed four catalysts for different Fenton-like technologies to achieve rapid and long-term degradation on active pharmaceuticals through functional modification of the active sites on the catalysts.The above methods systematically elucidate the production mechanism of reactive oxygen species and the degradation mechanism of active pharmaceuticals in Fenton-like technology,providing theoretical basis and technical reference for the development of active drug treatment technology.