Robust CNT-based conductive ultrafiltration membrane with tunable surface potential for in situ fouling mitigation

A membrane filtration process assisted by an electric field is effective for removing charged foulants from the membrane surface. In this work, a robust and conductive carbon nanotube (CNT) network membrane was prepared by adding alumina nanoparticles (NPs). The interaction between the CNT and alumina were characterized. The results indicate that alumina NPs were assembled on the sidewall of CNT bundles. After sintering, the mechanical stability of the network was enhanced due to the formation of a chemical bond between the CNT and the alumina NPs. Humic acid (HA) solution purification experiments of the as-prepared membranes were carried out. The membrane potential was adjusted from 0 to -0.5 V, the membrane stationary permeance increased by 63.4% and 30.6%, when using HA and HA/Na2SO4 solutions, respectively. Simultaneously, the HA rejection performance of the membranes also increased with the applied potential. The membrane fouling mitigation and the performance improvement are ascribed to the electrostatic repulsion of the negative potential in the membrane and the negatively charged HA. The filtration performance of the CNT-based membrane was compared with other conventional membrane processes. The results further demonstrate that the performance of this reported membrane is competitive, especially with the assistance of an electric field.