Preparation And Application Of Maynetically Responsive Anti-Pollution Oil-Water Separation Membrane

Membrane separation technology was widely used in oil and water separation.The core of membrane separation technology was the preparation of membrane.Nanofiber separation membranes could be prepared by electrospiinning.The nanofiber membrane structure was through-hole,which could increase the membrane flux,and the nanofiber could also improve the colliding and coalescence efficiency of the emulsion droplets.By adjusting the condition parameters of electrospinning,the structural properties of separation membranes such as fiber diameter,fiber morphology,fiber membrane porosity and pore size distribution could be effectively adjusted.It had a wide range of application prospects in the field of oil-water separation.However,in the process of membrane separation of oil-water emulsions,oily substances tended to adhere to the surface and block the membrane pores due to their high viscosity,resulting in a decrease in membrane flux and reducing the oil-water separation efficiency.By improving the superhydrophilicity of the oil-water separation membrane,the membrane pollution of the oil-water separation membrane could be effectively reduced.At the same time,the superparamagnetic nanoparticles grafted on the surface of the separation membrane could realize the self-cleaning and remove the oily pollutants on the surface of the separation membrane in an oscillating magnetic field,thus,enhancing the lifetime of the separation membrane.In this study,the oil-water separation membrane of polyacrylonitrile nanofibers(PAN)was prepared by electrospinning technique.The membrane had uniform morphology and high porosity.Furthermore,superparamagnetic nanoparticles(Fe3O4)with high saturation magnetic response were introduced by grafting modification to construct a super hydrophilic magnetic responsive anti-pollution oil-water separation membrane,which realized the separation of oil-water emulsion with high flux and high separation efficiency.The main conclusions were as follows:(1)Preparation of PAN membranes by electrospinning.Electrospinning solution was prepared by dissolving polyacrylonitrile(PAN,relative molecular weight 150 000)in dimethylformamide(DMF,organic solvent).Electrospinning parameters such as concentration of PAN spinning solution(3～20 wt%),spinning voltage(8～20 KV)and spinning time(0～1 h)were adjusted to select the preparation conditions of PAN with the best fiber morphology and porosity.When the concentration of PAN spinning solution was 15 wt%and the spinning voltage was 15 KV,the diameter of the nanofibers was about 700 nm.And the morphology and structure of membrane were uniform.The pore size distribution of the PAN membrane was concentrated in about 2～4 μm when the spinning time was 30 min,and the pore size structure of the PAN membrane could be separated from the oil-water emulsion.(2)Preparation of superparamagnetic Fe3O4 nanoparticles.Superparamagnetic Fe3O4 nanoparticles of different nanometer sizes were prepared by solvothermal and co-precipitation methods.The effects of different reaction conditions,such as temperature,reactant and time,on structure and magnetic response of the products were investigated.The optimal preparation method and conditions were screened.The results showed that the Fe3O4 nanoparticles prepared by the co-precipitation method had the smallest size.When the concentration of ferrous sulfate in the rection solution was 0.1 mol·L-1,and sodium hydroxide concentration was 0.2 mol·L-1.The reaction temperature was 100℃,and reaction time was 1 h.Fe3O4 nanoparticles with particle sizes ranging from 20 nm to 40 mm were obtained.The saturation magnetization of the Fe3O4 in the hysteresis loop was 75.7 emu·g-1,and the saturation magnetic response strength was 1.89 emu·g-1·nm-1 per unit length and mass.The product had a smaller particle size distribution and a higher saturation magnetic response intensity.(3)Preparation and performance study of magnetically responsive anti-pollution oil-water separation membrane.The superparamagnetic nanoparticles were modified by dopamine(DA)and grafted onto the PAN membrane modified by sodium hydroxide and hydrochloric acid(HPAN)to construct a super-hydrophilic magnetically responsive nanofiber membrane(PDA-Fe3O4-PAN)to carry out oil-water separation and self-separation.The results showed that the PDA-Fe3O4-PAN membrane was super-hydrophilic,and the contact angle of water in the air decreased from 141 ° to 0 °.When the oil-water emulsion flux was 2764 L·M-2·h·-1,the oil-water separation efficiency of the PDA-Fe3O4-PAN membrane for oil-water emulsions such as hexadecane,octane,and rapeseed oil were all greater than 95%.When the separation efficiency was less than 80%,the membrane was treated with an oscillating magnetic field.The oil-water separation efficiency recovered to more than 95%.After repeated for 8 times,the oil-water separation efficiency was still higher than 95%.