Negatively charged hollow crosslinked aromatic polymer fiber membrane for high-efficiency removal of cationic dyes in wastewater

The complete, high-efficiency removal of cationic dyes in industrial wastewater before discharge becomes particularly urgent due to their biological toxicity. The membranes have emerged for removal of dyes benefiting from free separation, cheap component and easy operation, and thus aroused increasing research interest. Herein, the negatively charged hollow crosslinked aromatic polystyrene (PS) fiber (HPF-C) membrane has been successfully synthesized by a rapid room-temperature crosslinking of linear PS in HPF membrane, followed by deep sulfonation. The sulfonated HPF-C (HPF-C-S) membrane showed high experimental equilibrium adsorption capacity of 443.6 mg·g −1 for basic red 46 (BR46) with initial concentration of 50 mg·L -1 . Its maximum adsorption capacity (346.0 mg·g −1 ) of methylene blue (MB) calculated by Langmuir model was about 5 times that of carboxylated cellulose fabrics (CCFs) membrane and higher than that of the most reported or commercially available nanofiber/nanoparticle adsorbents. Without external driven pressure, a flow rate of cationic dye solution through HPF-C-S membrane was up to 530 L·m −2 ·h −1 which was about 90 times that (6 L·m −2 ·h −1 ) of the CCFs membrane. The solution concentration through the HPF-C-S membrane always remained 0 mg L -1 (lower than the LODs of UV) before the permeation volume reached 4000 mL for 2 mg L -1 BR46 solution (In other words, 20 L of clean water could be obtained through per gram of membrane) and 1500 mL for 2 mg L -1 MB solution, respectively. The rejection ratio of 100% fully met the environmental criterion for wastewater disposal, indicating absolute superiority to the reported CCFs membrane that could not completely purify dyes. Moreover, the HPF-C-S membranes indicated excellent sustainability and stability. Besides, the kinetics, thermodynamics and mechanism behind these phenomena were studied.