Application Of Two-dimensional Semiconductor Catalysts For Treating Dye Wastewater

With the rapid development of urbanization and industrialization,the lacking of energy and increasing environmental problems have gradually threatened sustainable development of human society.Generally,the source of environmental pollution is caused by industrial dye wastewater,including industry of textiles,plastic,paper and leather.The toxicity,mutagenicity and carcinogenicity of dyes seriously threaten the health of human being.Therefore,a convenient way to remove organic dyes and pollutant discharge from industrial wastewater is still regarded as a severe challenge.Advanced oxidation technology,including fenton catalytic oxidation,photocatalysis technology and so on,has non-toxic,fast reaction,strong oxidation and other characteristics.However,the key point in advanced oxidation teccnology is the development of high performance catalysts.Two-dimensional（2D）nanomaterials have been intensively studied in optics,electronics,magnetism and catalysis for their novel physicochemical properties,especially large surface area and extremely thin thickness.In this dissertation,we researched the catalytic activity of nanosheets-based catalysts under non-light or visible light irradiation using 2D nanosheets as precursors.What is more,the obtained materials were characterized by XRD,FTIR,SEM,TEM,XPS,AFM,UV-vis.Their catalytic performances,stability and universality were also investigated by degrading Rh B and colorless organic pollution.The correlative works were summarized as follows:1.The protonic titanate was delaminated into negatively charged unilamellar titanate nanosheets（TNSs）by ethylamine aqueous solution.The non-light-driven rs-TNSs were flocculated by protons.The novel catalyst had been explored for degradation of organic pollutant with hydrogen peroxide（H2O2）in dark,which exhibited excellent performance for various dye conceration,p H and dyes,owning superior stability and reusability.What’s more,we have put forward the possible mechanism of rs-TNSs for decomposition of organic pollutant according to characterization techniques,including XPS、UV-vis and so on.2.Two-dimensional（2D）graphitic carbon nitride nanosheets（CNNS）with the negatively charge were exfoliated by alkali treatment.Graphene oxide（GO）and CNNS were used to trap Cd²⁺ that were transformed to CNNS/Cd S/r GO composite photocatalyst by thefollowed reduction and sulfuration treatment.The ternary photocatalyst with high visible light absorption and the gradient band structure promoted absorption of sunlight and the separation of photo-generation of charges.The photocatalyst exhibited enhanced photocatalytic performance in comparison with the single phase and their dual composites,as well as effect of wrap of nanosheets.Furthermore,this composite showed a superior stability,and maintained its high activity in the 5th cycle.Such facile strategy provided common and convenient route to fabricate multi-component heterostructures based on 2D nanosheets.3.A ternary photocatalyst CNNS/Cd S/TNS was obtained by assembling negatively charged CNNS and TNSs with Cd²⁺ ions.The high visible light absorption and the gradient band structure of the ternary photocatalyst promoted the photo-generation of charges and the followed separation of electrons and holes.The ternary composite photocatalyst exhibited the enhanced photocatalytic performance for the photodegradation of Rhodamine B under visible light irradiation in comparison with the single phase as well as their dual composites.Furthermore,this composite showed a superior reusability,and a high degradation ratio > 90 % was still achieved in the 5th cycle.