Cr(Ⅵ) Removal And Organic Pollutants Degradation Over Metal Sulphides And Their Composites

Organic pollution and heavy metal pollution in water bodies have become a major threat to human survival,and therefore have attracted worldwide attention.Photocatalysis is a sustainable technology that can remove pollutants with high efficiency and use sunlight as energy.Porous materials are very promising photocatalysts because of their porousness,large specific surface area and abundant active sites.Improve photocatalytic activity.The use of metal-organic framework（MOFs）as a sacrificial template to construct porous sulfides has attracted widespread attention.Not only can metal-organic frameworks（MOFs）have good photocatalytic performance under visible light,but also metal-organic frameworks can be used to promote iron.Based on the Fenton activity of MOFs to degrade new organic pollutants（PPCPs）.In this thesis,a hollow metal sulfide with MOF structure is prepared by vulcanizing MOF,which is used for photocatalytic reduction of Cr（VI）and degradation of dyes.The composite of metal sulfide and iron-based MOFs is also used to study refractory organic pollutants.The preparation of metal sulfides and their composites with high activity and high recyclability is realized.At the same time,the relationship between material microstructure and surface composition and material properties is deeply analyzed,and the mechanism of pollutant removal is discussed,which lays a theoretical foundation for the practical application of materials.The specific research content is as follows:1.A facile strategy was adopted to prepare porous Cd_0.5Zn_0.5S（CZS-X）nanocages by sulfurizing the rhombic dodecahedral ZIF-8 as precursor with thioacetamide（TAA）at different durations（0,1,3,5 h）,in which the fabrication mechanism of the porous CZS-X nanocages was clarified.The photocatalytic activities of CZS-X for Cr（VI）elimination and organic pollutants decomposition were assessed.The results revealed that CZS-3exhibited optimal photocatalytic activity under visible light along with satisfied recyclability and stability after several runs’operation.CZS-3 can achieve outstanding photocatalytic activities at neutral condition along with the co-existence of different inorganic ions/organic matters.As well,the CZS-3’s photocatalytic cleanup abilities toward both Cr（VI）and organic pollutants were explored in different actual water bodies.Finally,All the electrochemistry determination,active species identification as well as the ESR determination demonstrated the photocatalytic mechanism of CZS-3.2.MIL-68,a typical In-based MOF,has been studied in many fields due to its excellent performance.Facile preparation of MIL-68,suitable for scalable preparation and industrial applications,is of great significance.In this work,a method for the room-temperature preparation of rod-like MIL-68 at the nano-and micro-scales was developed for the first time,in which water or salts such as Na F,sodium formate,sodium acetate and sodium propionate were used as modulating reagents.It appears that these modulating reagents can promote the deprotonation of terephthalic acid and the hydrolysis of indium salt to accelerate crystal nucleation.The size of MIL-68 can be controlled by changing the modulating reagents.Hollow porous In₂S₃ particles composed of assembled ultrathin nanosheets were obtained via sulfidation treatment using MIL-68 as a self-sacrifice template,and the obtained In₂S₃ exhibited excellent photocatalytic activity toward Cr（VI）reduction and methyl orange degradation under LED visible light irradiation.Furthermore,the photocatalytic mechanism and reusability were studied.3.Series of MIL-100（Fe）/CoS composites（Mx Cy）were facilely fabricated using ball-milling method.The optimum material（M50C50）exhibited extremely higher Fenton catalytic activity toward BPA than pristine MIL-100（Fe）and CoS,in which 100.0%BPA（50 ppm）removal efficiency was achieved in the presence of M50C50 and H₂O₂.The great improvement of BPA degradation was attributed to the synergetic effect between MIL-100（Fe）and CoS with the synergistic factor being 95.7%,in which the Fe-S bonds formed at the interface of the two components facilitate the Fe³⁺/Fe²⁺cycle by improving the electron mobility both from Co to Fe and from S to Fe.Furthermore,the influence factors like negative ions and pH values on the degradation of M50C50 were explored.The possible reaction mechanism was confirmed by the results of both active species capture tests and electron spin resonance（ESR）determinations.It was found that M50C50 demonstrated good reusability and water stability as the morphology and structure was not changed obviously after five runs.