Selective and Adjustable Removal of Phenolic Compounds from Water by Biquaternary Ammonium Polyacrylonitrile Fibers

A series of biquaternary ammonium-functionalized fibers were developed to efficiently realize selective removal of phenolic compounds from water. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy were employed to determine the successful preparation of functionalized fibers. Scanning electron microscopy, X-ray diffraction (XRD) patterns, and elemental analysis were used to analyze the microstructure and composition. First, the adsorption result shows that a fiber with a three-carbon alkyl chain (PAN(BQAS-3)F) has the maximum adsorption capacity for 2,4-dinitrophenol (2,4-DNP) (406 mg g(-1)). Electrostatic attraction and pi-pi interaction are the main forces in adsorption. The adsorption kinetics studies display that PAN(BQAS-3)F can rapidly adsorb 2,4-DNP in 10 min and achieve equilibrium within 20 min. The adsorption process of 2,4-DNP by PAN(BQAS-3)F follows the Langmuir model, demonstrating that the process is more consistent with monolayer adsorption. What is more, the adsorbent PAN(BQAS-3)F can be reused after 10 adsorption/desorption cycles and still maintains an excellent removal rate (99%). Otherwise, PAN(BQAS-3)F was used in a continuous flow process and exhibited a removal rate of more than 96%, which certifies that PAN(BQAS-3)F is an excellent adsorbent and can be utilized in practice.