Controlled Synthesis Of Novel Zns-based Carbon Nanocomposites And Its Application In Pollutana Removal

Photocatalysis can utilize sunlight to mineralize organic pollutants,which is an effective and green means to remove organic pollutants from water.Therefore,it is of great significance to prepare efficient and stable photocatalyst.In addition to TiO2 and ZnO,ZnS is also an important photocatalyst and has the advantages of non-toxic,cheap,photogenerated carrier redox ability and so on.However,ZnS nano-catalysts have low utilization rate of sunlight and only realize the ultraviolet light response;Photogenerated electron-hole(e-/h+)is easy to compound resulting in low catalytic activity and poor stability;Preparation needs expensive equipment and harsh reaction conditions which is low output;The size and dispersion of ZnS nanoparticles are difficult to control.In view of the problems existing in the application of ZnS nano-photocatalyst,the layered transition bimetallic hydroxides(LDHs)intercalated with salicylate(Sal-)were used as molecular precursors in this paper.ZnS-C nanocomposites(ZnS-C)and Fe doped ZnS-C nanocomposites(Zn(Fe)S-C)were prepared by direct bottom-up solid-state method.Its composition and structure were studied,and it was applied to the visible light catalytic degradation of organic pollutants to explore its visible light catalytic activity and cycling stability.The main research contents are as follows:1.Salicylic acid intercalated two dimensional layered zinc hydroxide(Zn-Sal LDHS)nanosheets which used as molecular precursors were prepared by self-assembly of cheap water-soluble salts(zinc nitrate,sodium salicylate)in aqueous solution.The visible light ZnS-C nanocatalysis was prepared by one-step solid state pyrolysis in an inert atmosphere.Characterization methods such as XRD,FTIR,SEM,Ramam,XPS,BET and so on were used to study the composition,structure and properties of ZnS-C nano-catalysts.The results show that the Zn-Sal LDHs are 180-550nm nanosheets,which still maintain two-dimensional sheets structure after in-situ curing.Solid state pyrolysis realized the transformation from small organic molecules to functionalized graphitized carbon,and realized the controllable preparation of ZnS nanoparticles(10-23 nm).The high purity ZnS nanoparticles are uniformly dispersed in the mesoporous graphite-carbon matrix and the protective effect of graphite-carbon prevents the oxidation of S atomic,which makes the material have high stability.The surface of graphite carbon contains a large number of hydrophilic functional groups(-OH)and strongly interacts with ZnS through O atoms.The sensitization of graphite carbon broadens the visible light response range.And the band gap absorption edge shifts to 416nm.The catalytic degradation of methylene blue is excellent under visible light.Degradation rate can reached 92%under visible light irradiation 240min which is better than commercial commercial TiO2.After 4 cycles ZnS-C nanocatalyst is still maintain a high catalytic activity.2?The two dimensional layered hydroxide(Zn1-xFex-Sal LDHs)(x=0,0.05,0.1,0.2)precursors of salicylic acid intercalation were prepared by using the adjustable properties of metal cation in the laminates.A novel iron ions doped ZnS-C nano-photocatalyst(Zn(Fe)S-C)was prepared using Zn1-xFex-Sal LDHs as molecular precursors by in-situ sulfurization and one-step solid pyrolysis in the presence of no template agent and additional carbon source.Many characterization methods were used to study the composition,structure and properties of ZnS-C nano-catalysts.The results show that the precursors of nanosheets can be effectively regulated at 80-550 nm by adjusting the doping amount of Fe3+.The material composition,particle size(10-28 nm)and reactive site can be effectively controlled by adjusting the solid-state reaction temperature.Zn(Fe)S nanoparticles are uniformly dispersed and coated by two to four functionalized graphite-carbon layers.Graphite carbon not only improves the dispersion of Zn(Fe)S nanoparticles,but also realizes the visible light response of Zn(Fe)S nanoparticles.Its excellent electrical conductivity improves the e-transfer rate and promotes the e-/h+ separation.At the same time,iron ions doping introduces the impurity(defect)energy level into the ZnS crystal lattice,which broadened the optical absorption range and the absorption edge of the band gap shifted to 738 nm.The catalytic degradation rates of organic pollutants such as aromatic heterocyclic dyes,azo dyes and triaryl methane dyes were all over 90%in 90 min under visible light,The first-order reaction kinetic constants were 0.02505 min-1,0.029 min-1 and 0.028 min-1 respectively.The catalytic rates of Zn(Fe)S-C nanocatalysis were 9.7,8.3 and 22.2 times higher than commercial catalyst P25 under the same conditions.The Zn(Fe)S-C nanocatalysis exhibited excellent catalytic activity and cycling stability.