The Research Of Porous SiC And Its Modification On The Filtration Properties Of Oily Wastewater

Oily wastewater has a serious effect on the environment,plant growth,animal health,and so on.How to treat oily wastewater purification is urgent.Membrane separation technology has been paid attention to because of its high efficiency and low cost.Asymmetric silicon carbide porous ceramic membrane has high strength,high hardness,good chemical stability,long service life,easy regeneration and separation efficiency.As the core components of filtration it has a broad prospects in application.Asymmetric membrane is composed of support,transition layer and microporous membrane.Support with large pore for high permeability was a must of high strength,surface membrane formed of fine particles has small open pore size to sepeart different phase,and the designed transition layer must meet the need that grains in surface membrane cannot filled into the pore of support.In this study porous silicon carbide ceramic supports with different porosity were fabricated by adjusting pore-forming agent.The effects of the thickness and pore structure of the porous SiC on the simulated oil-wastewater emulsion were studied.The silicon carbide slurry with high stability and suitable viscosity was prepared by optimizing the dispersant,defoaming agent and solid content.Finally,use the dip-coating method to prepare silicon carbide membrane and the Teflon hydrophobic film on the inner surface of the tubular silicon carbide support.And microscopic morphology,phase and cross-flow filtration effect of simulative oily wastewater emulsion test had been analysiedFirstly,35 ?m silicon carbide particles,low-temperature sintering aids,dextrin solution and pore-forming agent of petroleum coke were staring materials.After mixing these raw materials,the mixture was pressed at 50 MPa in a tubular mold,then was sintered at 870 ?.The wall thickness was adjusted by different mold.When improving pore forming agent from zero to 20%,the open porosity increase from 40.12% to 52.13%,the density from 1.71 g/cm3 to 1.31 g/cm3,and the flexural strength from 20.664 MPa to 13.78 MPa.The result of cross-flow filtration show the permeation flux of water and simulated oil-wastewater emulsion increase linearly with the wall thickness of porous tubular silicon carbide support from 50 mm to 30.16 mm.When the wall thickness was fixed,the permeation flux of water and simulated oil-wastewater emulsion increased rapidly.The tubular silicon carbide supports with different porosity can play a certain role druing the treatment of simulated oily wastewater.Secondly,10mm*10mm*4mm rectangular silicon carbide specimen were dipped from Teflon solution after immering for 1 h,3 h,6 h and 12 h,respectively.After dried,it was sintered at 270? for 3 h and 337? for 1.5 h.With prolonging immersion time,the contact angle of Teflon hydrophobic film to water was improved from 134.65° to 143.56°,to simulated oily wastewater from 61.02° to 89°,the surface roughness from 13.3 ?m to 6.4 ?m.The outer surface of the support was sealed and then the tubular specimen was immersed for 1 h and sintered,the Teflon hydrophobic membrane with uniform film was prepared on the inner surface.The results of cross-flow filtration shows that the permeation flux of water and simulated oily wastewater emulsion increased.And the increase of the amount of emulsion permeation is greater than that of water permeation.The effect of Teflon hydrophobic membrane on the seperation of simulated oily wastewater emulsion is more significant.Finally,the stabilized silicon carbide slurry was prepared by optimizing the dispersant,defoaming agent and solid content.It had 1.5%CMC solution and 45% solid content.The silicon carbide support was vertically dipped from prefabricated slurry at 50 mm/min,then dried and sintered at 850?.Uniform silicon carbide Membrane was obtained on the inner surface of the support,silicon carbide membranes with different thickness by dipping repeatly were be obtained.The results show that as the increase of the thickness,the H2 O and simulated oily-wastewater emulsion infiltration decreases rapidly.However,the effect of the seperation of the simulated oil-containing wastewater emulsion were improved obviously.Under the same conditions,the seperation effect of the filter pulled two times on the simulated oil-wastewater emulsion was close to that of Teflon hydrophobic membrane.