| Since modern times,with the rapid development of global industrial technology,various oil pollution in water bodies have been produced.There are currently several purification methods for oily wastewater: gravity separation,coarse-graining,electrolytic coagulation flotation,coagulation,oil adsorption,and membrane separation.Among them,the adsorption method and membrane separation method have received extensive attention in the purification of oily wastewater due to their low cost,simple operation and excellent performance.It has become a research hotspot to develop new membrane materials with high porosity,special wettability,and high separation efficiency by electrospinning technology and selecting ideal materials.Natural organic material loofah is a potential oil-water separation material,which has the advantages of reproducibility,low consumption,high oil absorption,low price,and biodegradability.However,the intermolecular hydrogen bonds generated by its polyhydroxyl structure limit its dissolution in conventional solutions and its application in electrospinning.In response to the above problems,we use loofah as the matrix,add synthetic organic materials polymethyl methacrylate(PMMA)and polyvinylidene fluoride(PVDF)to increase its spinnability,and prepare the core-shell structure composite fiber membrane with loofah as the core by the modified Janus nozzle in one step,which can be used for the purification of oily wastewater.This work selects natural plant-derived cellulose loofah as the matrix material,adds hydrophobic and lipophilic PMMA and PVDF respectively to prepare a core-shell structure loofah-based composite membrane by the modified Janus nozzle electrospinning technology.The oil adsorption performance and switchable oil-water separation performance of the membrane were studied.The research content is as follows:(1)In this study,we use 3 wt% loofah solution and 25 wt% PMMA solution to prepare composite loofah/PMMA membranes by the modified Janus nozzle electrospinning.When increasing the concentration of the PMMA solution,the microstructure of the electrospun membrane transforms from microspheres to fibers by pure PMMA electrospinning.The average diameter and surfave wettability of the composite fibers can be controlled by adjusting the advancing speed of the PMMA solution during electrospinning.During the polymer jet process,the PMMA solution with high mobility,low viscosity and low surface tension is more likely to migrate to the position of the highest shear rate on the fiber surface to coat the loofah cellulose to form a core-shell structure.The prepared core-shell structure loofah/PMMA composite fiber membrane exhibits excellent hydrophobicity under harsh conditions such as strong acid,strong alkali,and high salt.In the oil adsorption and membrane separation experiment,the composite fiber membranes show good oil adsorption and water-oil separation capabilities.(2)Based on the above research,3 wt% loofah solution and 10 wt% PVDF solution are used to further prepare the loofah/PVDF membrane by the modified Janus nozzle.When the advancing speed of the loofah solution and PVDF solution are 0.3 m L/h and 0.5 m L/h respectively,the average fiber diameter is the smallest of 332 nm and the PVDF-β phase crystal structure is formed.By adjusting the length of the Janus nozzle,the motion state of two immiscible fluidsand and the formation process of the core-shell structure are determined.The PVDF component unidirectionally wraps the loofah component and occupies the shell layer to form the core-shell structure.The shell layer of the fiber is hydrophobic and lipophilic PVDF,and the core layer is hydrophilic and lipophilic loofah.so a metastable hydrophobic surface is constructed for switchable separating oil-water mixtures.That is,the dry fiber membrane can separate the oil from the oil-water mixture,and the membrane wetted by water can separate the water from the mixture.This composite fiber membrane has good reusability and emulsion separation ability. |
PDF Full Text Request