Scalable, Acid-Resistant Amidoxime-Modified Polyacrylonitrile Hollow Fiber for Removal of Hexavalent Cr(VI) Ions in Wastewater

Abstract

Hexavalent chromium (Cr(VI)) wastewater poses a severe threat to the ecological environment and human health due to its high toxicity and poor degradability. At present, the development of Cr(VI)-removing materials with high adsorption capacity, excellent stability, and scalable preparation still remains a challenge. Herein, scalable amidoxime-modified polyacrylonitrile (AOPAN) hollow fibers were facilely fabricated via a wet-spinning and chemical modification strategy. The results demonstrate that AOPAN fibers retain a porous structure and the experimental maximum adsorption capacity for Cr(VI) reaches 279.53 mg/g at pH = 2, with an initial concentration of 500 mg/L at 318 K. The adsorption process conforms to the pseudo-second-order kinetics and the Langmuir adsorption isotherm model and is an endothermic, spontaneous, and entropy-increasing process. The adsorption mechanism is attributed to the synergistic effect of electrostatic adsorption-reduction-chelation: amidoxime groups are protonated to form cationic sites under acidic conditions, and nitrogen-containing groups further reduce Cr(VI) to Cr(III). In addition, the material exhibits outstanding acid resistance and anti-interference ability against coexisting ions, with the adsorption capacity remaining at 68.5% after 8 cycles of reuse. Dynamic filtration experiments confirm that AOPAN fibers achieve a Cr(VI) removal rate of 93.2% and a permeation flux of 380 L/(m2·h) at 0.6 bar. This work provides a feasible solution for the industrial treatment of Cr(VI)-containing wastewater and holds broad practical application prospects.