A tris(hydroxymethyl)aminomethane-modified polyimide membrane with efficient organic solvent resistant performance and high separation selectivity for dye/salt separation

Efficient separation of dyes and salts from textile wastewater is still a great difficulty. Herein, a tris(hydroxymethyl) aminomethane (Tris)-modified polyimide (PI) membrane was developed, which was effective, easy-to-fabricate, and versatile with high-separation-selective performance. With the introduction of Tris, the roughness, hydrophilicity and negative zeta potential of the membranes were increased, and the pore size was reduced. At 3 bar, the representative membrane exhibited high permeate flux (176–206 L·m−2·h−1) and high rejection (>97 %) to four common dyes and excellent solvent resistance to seven organic solvents, indicating that PI/Tris membrane had potential for application in dye wastewater containing complex organic solvents. Furthermore, the PI/Tris-modified membrane could selectively separate dyes and salts, and presented high dye rejection (>99 %) and low salt rejection (≈7 %) as well as high selectivity (separation factor = 103) for Direct Black 38/NaCl mixture. In particular, the PI/Tris-modified membranes outperformed many contemporary separation membranes in terms of separation efficiency of dye/salt mixtures. In summary, this PI/Tris membrane developed in this study has a promising future in the field of industrial dye wastewater treatment.