Febrication Of Special Membranes With Super-aligned Carbon Nanotubes And Their Performance For Oily Wastewater Treatment

Membrane separation technology is an important technology for oily wastewater treatment.However,the existing membrane materials have limitations of low separation efficiency and serious membrane fouling problem,which seriously hamper the further development of membrane-based oil-water separation technology.In this study,based on the principles of super-aligned carbon nanotubes（SACNTs）,interfacial modification,and electrically assisted antifouling strategy,different kinds of novel conductive membranes with special wettability were prepared,aiming to achieve efficient oil-water separation efficiency while inhibiting the development of membrane fouling.The antifouling mechanism of different conductive membranes in the electrically assisted membrane separation processes was analyzed.A series of nonpolar SACNT membranes with different numbers of stacked layers were prepared based on a SACNT array and cross-stacking fabircation technology.The surface physiochemical properties and filtration–retention performance of the SACNT membranes were systematically characterized,and their antifouling performance was investigated using model foulants.The results show that the 200-layer-SACNT membrane achieves a high specific pure water permeability(14.4×10⁶ m s^-1k Pa^-1),which is～2.3 times higher than that of a 0.22μm commercial membrane,while maintains a better retention capability.In addition,the SACNT membrane is hydrophobic and oiphilic in the air,thus favorable for oil-water separation,but its permeability is low.In the process of separation of model foulant solution,the SACNT membrane showed high permeation flux and cleaning efficiency.Based on the layer-by-layer fabrication technology of SACNT membrane and nano-SiO₂ self-assembly grafting strategy,a novel SiO₂/SACNT nanocomposite membrane with super-hydrophilic/underwater superoleophobic properties was prepared.The contact angle test shows that the SiO₂/SACNT nanocomposite membrane is superhydrophilic（～0°）in the air and superhydrophobic（～155°）under water.The results of underwater oil rolling experiment and oil-water separation tests show that the SiO₂/SACNT nanocomposite membrane has ultra-low oil adhesion and excellent oil-water separation performance.The 10-cycle oil-water emulsion separation experiment showed that the permeability of the SiO₂/SACNT nanocomposite membrane was significantly increased compared with that of the SACNT membrane,demonstrating improved anti-irreversible fouling ability.Based on typical model foulants,the antifouling behaviors of the SACNT and SiO₂/SACNT nanocomposite membranes in the process of electroassisted membrane separation were further studied.In the study with the mixed model foulant solution,the growth rate of transmembrane pressure of the two conductive membranes（as cathodes）decreased significantly,which indicated that the applied electric field was beneficial to the inhibition of membrane fouling.The analyses of membrane fouling resistance showed that the applied electric field was beneficial to the inhibition of irreversible fouling.In addition,the effect of electric field,the change of Zeta potential on the surface of the pollutant,and the complex interactions between Ca²⁺/Mg²⁺and the pollutants have a significant influence on the development of membrane fouling.