Fabrication Of Self-assembled 00D-2DBi₂MoO₆-g-C₃N₄ Photocatalytic Composite Membrane With Visible Light Water Treatment Performance

Water resources are the precious wealth of mankind.However,in recent decades,with the progress of heavy industry and the growth of population,water pollution has changed into the Achilles’Heel of human development,and we are in a dilemma between protecting water resources and developing the economy invariably.Membrane treatment technology stands out among many traditional water treatment technologies due to its strong pollutant removal ability,environment friendly,high efficiency and energy saving.However,the increase of transmembrane pressure drop and the decrease of water flux caused by cumulative fouling on the membrane surface have become the bottleneck restricting the wide application of membrane.Therefore,researchers have done some research,such as membrane surface modification or biological quenching,to reduce or even reverse membranes contamination is urgently needed to maintain the filtration activity and allow the composite membranes to function well.Nonetheless,the hydrophilic modification of membrane can prevent the adsorption of pollutants on the membrane surface only,but could not do anything for the degradation of pollutants.In order to find a reasonable solution,a combination of photocatalytic technology and membrane separation technology emerged as the times require.The self-cleaning function of photocatalytic membrane technology derived from the combination of photocatalytic technology and membrane substrate can well solve the problem of irreversible pollution accumulated in the operation of the filter membrane,which is of great research value.Compared with the traditional UV-response photocatalytic film,visible light response photocatalytic film can greatly improve the utilization of sunlight,which is also one of the research hotspots in recent years.Therefore,we designed a highly efficient 0D-2D Bi₂Mo O₆-g-C₃N₄ photocatalyst and constructed a photocatalytic membrane based on this catalyst.The specific research contents are as follows.0D-2D Bi₂Mo O₆-g-C₃N₄/PVDF photocatalysis membrane was prepared by vacuum assisted self-assembly（LBL）method.The 2D g-C₃N₄ nanosheets prepared by thermal polycondensation and 0D Bi₂Mo O₆ prepared by hydrothermal method were combined by impregnation method.The surface of the membrane was coated with PDA to introduce catechol group.The good adhesion between the film and the photocatalyst was confirmed by pure water immersion,vibration and shear test.The degradation efficiency of TC reached 67.75%by static photocatalytic experiment,which verified its catalytic performance.In the test of rejection rate,the rejection rate of the composite membrane to sodium alginate is more than 90%,and the rejection rate to bovine serum albumin is more than 80%.Under visible light irradiation,the reversible scaling（Rr）gradually replaced the irreversible scaling（Rir）as the main scaling factor.Under visible light irradiation（k>420nm）for 30min,the flux recovery rate of the composite membrane reached more than 85%.After four cycles of experiments,the maximum flux recovery rate of the membrane remained above 75%.The above results show that the multi-dimensional functional layer morphology increases the contact area of the membrane to pollutants,and improves the mechanical stability,retention performance and self-cleaning performance of the composite membrane.In this paper,we not only prepared a new type of photocatalytic film by vacuum assisted self-assembly method,but also helped us to further understand the relationship between the multi-dimensional of photocatalytic materials and the improvement of photocatalytic film performance.