Fabrication of high performance carboxylated poly (aryl ether nitrile) membrane for dye/salt selective separation

Abstract

Membrane with high performance for dye/salt mixed solutions effective separation is desired for textile wastewater treatment. In this paper, a carboxylated poly(aryl ether nitrile) (PEN-COOH) tight ultrafiltration membrane was prepared to fractionate dye/salt by non-solvent induced phase separation with PEG6000 as additive. Due to the synergistic effect of the strong electricity absorption of inherent -CN on poly(aryl ether nitrile) and the ionization of -COOH, PEN-COOH membrane surface showed a strong electronegativity, which was beneficial to the efficient dyes removal by electrostatic repulsion effect. Meanwhile, it was conducive to moderately reducing the membrane denseness to improve permeability. Dextran solute retention experiment showed that PEN-COOH membrane had a molecular weight cut-off of 31,000 Da, corresponding to an effective surface average pore of 7.7 nm. It had a hydraulic permeability of 2.9 L m−2 h−1 bar−1. Compared with those membranes prepared by commercially available materials, PEN-COOH membrane showed unparalleled separation performance advantages. Its pure water flux reached 401.2 L m−2 h−1, while maintaining high retention efficiency of electronegative dyes (> 99%) and low rejection rate of salts (< 10%) under 0.1 MPa driving pressure. PEN-COOH membrane also showed good anti-dye-fouling durability and excellent dye separation performance under varied pH, temperature and pressure, making it a promising membrane for textile wastewater treatment.