Carbon nanotube incorporated polyphenol electro-responsive ultrafiltration membranes toward dye separation

Carbon nanotube (CNT) is a promising raw material for membrane fabrication due to its good electrical conductivity, great specific surface area, and special piping structure. In this report, tannin (TA), CNT, and D-aspartic acid (DAS) were co -deposited on the surface of polyethersulfone (PES) ultrafiltration membrane to construct an electrically responsive coating. The membrane can maintain the high electrical conductivity while avoiding the membrane defects due to the accumulation of CNTs and the different lengths of chain segments in the process of CNT co-blending to form the membrane. The results show that the average pore size of the membrane is reduced from 19.55 nm to 8.165 nm, and the retention capacity is greatly improved, showing good separation efficiency (99.5 %) and hydrophilicity (water contact angle of 13°). Through adsorption and electric field deflection, CNT endows the membrane with the ability to selectively separate dyestuffs with different electrically charged properties. Long-term stability tests show that the modified membrane still maintains a high level of pure water flux and conductivity after seven days of operation. This paper is of exploratory significance in the field of electrically responsive smart membranes for dye separation. The membrane developed in this study exhibits unique selective separation performance and can dynamically adjust its separation efficiency by externally controlling the electric field strength. This demonstrates its excellent intelligence, making it highly promising for applications in electrically responsive intelligent separation membranes. Additionally, it offers a novel approach for treating dye-containing wastewater using electrically charged functional membranes.