Photocatalytic Mechanism Of MXene And Dye Wastewater Treatment

With the development of society and economy,human demand for water resources is increasing day by day.At the same time,the continuous discharge of industrial wastewater,such as dye synthesis and printing and dyeing,has caused serious pollution and aggravated the shortage of water resources.In order to improve the water pollution problem,scholars have strengthened the research on the science and technology of sewage treatment.As an emerging two-dimensional layered nanomaterials,MXene has shown remarkable advantages in photocatalysis and membrane separation due to its special structure.Firstly,MXene with clear laminate was obtained by etching Ti3AlC2 with different methods.The decolorization and degradation of organic dyeing solution was taken as the research object,and the photocatalytic treatment of MXene with different amounts of additives and different pH conditions under three environments of simulated ultraviolet light,fluorescent and darkness.It was found that under the conditions of simulated fluorescent and ultraviolet light,the dyes used in the experiment could degrade rapidly at different pH levels.In addition,MXene was recovered from Methyl orange dye catalyzed at pH is 2 and ultraviolet light,and the degradation rate of MXene-Ti₃C₂ in three comparison experiments during 4 h reached more than 96%,which indicated that MXene-Ti₃C₂ is recyclable.With increasing number of cycles,the degradation rate increases.The material irradiated for a longer time has stronger photocatalytic performance.In order to explore the photocatalytic decolorization and degradation mechanism of dyes by MXene,the semiconductor properties of MXene nanosheets were calculated by density functional theory.It was found that MXene with Ti₃C₂ structure on the surface had strong metal conductivity.SEM,XRD and XPS were used to characterize the phase and morphology of the precursor Ti₃AlC₂,Ti₃C₂ and Ti₃C₂ under high temperature hydrothermal conditions.The results have shown that nano TiO₂ chips grow up in Ti₃C₂ as a built-in titanium source under high temperature hydrothermal conditions,leading to the formation of TiO₂&Ti₃C₂ nanometer composites,that is heterogeneous junctions.Ti₃C₂ has strong metal property and plays a co-catalyst role in the experiment,enhancing the separation between electron hole pairs,prolonging the life of its photogenic carriers and improve the photocatalytic performance.A series of MXene/CA mixed matrix Membranes（MMMs）with excellent comprehensive properties were prepared with MXene nanometer sheets as inorganic nano-additive and cellulose acetate（CA）used as polymer matrix material.The membranes with the MXene content of 3 wt.%,the rejections to Congo Red solution,Gentian Violet solution and Na₂SO₄were 99%,100%,and 89.6%respectively,when measured at 0.3 MPa.The membranes have good retention effect and relatively high flux（about 4.8 L/m² h）.The results showed that the membrane had excellent separation selectivity for dyes and inorganic salts,In addition,the membrane performance did not decrease after 12 days of static immersion in 50%DMAc solution,and the crosslinked membrane showed good solvent resistance.Moreover,the introduction of hydrophilic MXene improved the anti-fouling performance of the separation membrane.