Preparation of high-conductivity films using efficiently dispersed carbon nanotube slurry for “Dye/salt” selective separation

To overcome the technical bottleneck caused by imperfect conductive networks in films, which limits separation selectivity, this study employed a novel polymer - amide - sulfonic acid gradient coating strategy to achieve near-individual dispersion of high-purity carbon nanotubes (CNT). On this basis, a conductive carbon nanotube@polyvinylidene fluoride (CNT@PVDF) film was prepared via phase separation, showing a conductivity of up to 4.99 S·m –1 . By regulating the CNT slurry concentration to reduce mass-transfer resistance during phase separation, and through the combined mechanisms of Donnan rejection, the electroosmotic flow effect, and physical filtration, the separation performance of the film was significantly improved. Under the optimal CNT content (6 wt%) and an applied voltage of –3 V, the film showed a pure water flux of 134.52 L·m –2 ·h –1 , with rejection of 98.13% for Bovine Serum Albumin (BSA) and a selectivity factor of 84.7 for Congo red/sodium chloride (CR/NaCl), exceeding currently reported values. Furthermore, after 10 cycles, the film retained about 98% of its CR/NaCl selectivity factor and showed a flux recovery rate of 96.2% compared with the initial use, indicating favorable antifouling ability and long-term operational stability. These results demonstrate the considerable potential of high-purity CNT slurries in constructing conductive separation films and provide a new strategy to address the trade - off between permeability and selectivity in dye/salt separation processes.