Application And Research Of Graphite Carbon Nitride Nano/Microspheres And Functional Membranes Toward Water Environment Remediation

Complex wastewater purification is one of the great challenges in the water environment restoration field.The photocatalytic technology driven by sustainable solar energy and membrane separation technology without chemical consumption are ideal choices for complex wastewater purification.However,the difficulty of recovering micro-nanometer sized photocatalyst powder and the problem of membrane fouling seriously restrict their wider application.Photocatalytic membrane technology has become a new research hotspot and drawn broad interdisciplinary attention in the water environment remediation field owing to it combines photocatalysis and membrane separation in one unit to effectively solve the problems of photocatalyst powder recovery and membrane fouling.Here,this study prepared high-efficiency 3D graphitic carbon nitride nano/microspheres(CNMS)and constructed a multifunctional photocatalytic composite membrane based on CNMS for continuous purification of complex wastewater.The specific contents of this thesis are described as follows:3D graphitic carbon nitride nano/microspheres was prepared by low-temperature solvothermal method.The space utilization and solar energy absorption capacity of g-C₃N₄were improved.The J-type aggregate was improved during the solvothermal process,which make it have smaller band gap(1.75 eV)and higher photocatalytic efficiency.In addition,under the condition of low molar ratio of raw materials,the shortage of reaction monomers led to the incomplete polymerization of in-plane triazine heterocycles,which introduced defects into the CNMS lattice,promoted the separation of photogenerated electrons and photogenerated holes,and significantly improved the photocatalytic activity of CNMS.Inspired by superhydrophilic sphagnum,a composite membrane was engineered by depositing CNMS with plentiful wrinkles onto the polyacrylic acid functionalized carbon nanotubes(CNTs-PAA)mesh.The hydrogen bonding force combines membrane separation and photocatalysis in one unit to achieve multi-functional wastewater treatment.Through coupling unique structure and chemistry properties,the CNTs-PAA/CNMS composite membrane presents superhydrophilicity and underwater superoleophobicity.The spherical structure gives the membrane higher space utilization and flux,which makes the CNTs-PAA/CNMS membrane has excellent visible light-driven self-cleaning ability and higher purification efficiency.The unique layered functional design gives the membrane all-in-one purification ability,which can maintain its excellent emulsion separation(with a maximum flux of 5557±331 L m^-2 h^-1 bar^-1and an efficiency of 98.5±0.6%),photocatalytic degradation(with an efficiency of 99.7±0.2%)and antibacterial(with an efficiency of?100%)ability even after cyclic experimental processes.The excellent complex wastewater purification ability and self-cleaning ability of this all-in-one membrane represents its potential value for water environment remediation.