The Preparation Of Montmorillonite Modified Membrane And Its Research In Oily Wastewater Treatment

Membrane technology with low energy consumption,high separating efficiency,easy operation,no health effects,and gradually becomes the most development outlook water treatment technology in water treatment.The pollution of membrane is inevitable in the applications of membrane,and membrane modification is one of the effective means to reduce membrane fouling.In this research,montmorillonite(MMT)was used as a modifier,through the blending modification to combine organically the polyvinylidene fluoride(PVDF)and organic montmorillonite(OMMT),OMMT/PVDF composite ultrafiltration membrane was prepared by phase inversion method.The effects of properties and additions of MMT on the membrane permeability,the microstructure,and the change of membrane resistance in membrane filtration process of oily wastewater were explored.The main conclusions were listed as followings:(1)Through the modification in organic way,the spacing of layers of the MMT(001)was increased from 1.24 nm to 1.74 nm.The result of FTIR showed that the characteristic peak of the intercalation agent was appeared.It showed that the intercalation agent can enter the MMT layer and increase the distance between layers of MMT.There was no new characteristic peak in the infrared spectrum of the modified membrane,indicating that the MMT would not lead to crystalline changes in the PVDF.In addition,the modified effect of OMMT on PVDF was more significant than MMT.(2)When the amount of OMMT was 2wt%,the rejection of the modified membrane reached the maximum,83.09%.When the addition amount was 3wt%,the membrane flux reached the maximum,2.3 times that of the original membrane;the average pore size of the modified membrane was increased from 22.79 nm to 59.76 nm(3wt%)of the original membrane,which was about 3 times higher;the hydrophilic angle was lowest at 2wt%,59.96°,and decreased by 25% at 79.25° before modification;tensile strength of the membrane reaches the maximum of 5wt%,which was 2 times that of the original membrane;the film breaking strength reaches the maximum when the addition amount was 2wt%,which was 1.8 times that of the original membrane.The tests showed that after the modification,the filtration performance,hydrophilicity and mechanical properties of the membrane were all improved.When the amount was 2wt%,the overall performance was the best.(3)The SEM images illustrated that the fracture surface of both the original membrane and the modified membrane had a similar cross-section structure and all exhibit an asymmetric structure,which indicated that the OMMT did not affect the film forming performance of PVDF.AFM revealed that,compared with the original membrane,the roughness of modified membrane became larger,from 73.7 to maximum value 138.0 nm,the hydrophilicity of the membranes was enhanced.(4)The removal rate of oil by the modified membrane reached 83%,which was 1.52 times that of the original membrane;the removal rate of COD reached 80%,which was 1.25 times that of the original membrane,it showed that the treatment effect of modified membrane on oily wastewater was better than that of original membrane.After being contaminated,the surface of both membranes was covered with gelatinous material,but there was no significant change in the cross-section,showing that the membrane intercepting action was dominated by the formation of the filter cake layer on the membrane surface.The two kinds of membranes had the same trend of resistance,and their drag growth had a rapidly increasing area and a stable area.During the filtration process,the total membrane resistance of the modified membrane was always smaller than it of the original membrane at any time,and the increase was also smaller than that of the original membrane,which proofed that the modified membrane had stronger anti-fouling ability.According to the changes of resistance,it was found that the main cause of the pollution in the early stage of membrane filtration was the adsorption of the membrane to the pollutants and the blockage of the membrane poresm,the later stage of membrane filtration was the formation of the filter cake layer.