Quaternary Ammonium Groups-containing Ion Exchange Fiber: Synthesis, Characterization And Adsorption Properties Of Cr (â…¥)

Due to various application forms and excellent adsorption performance, quaternary ammonium group-containing ion exchange fibers are widely used in element separation and enrichment, resource recovery and recycling, environmental protection, pharmaceutical industry, etc. A quaternized aminated poly(acrylonitrile) (QAPAN) fiber was prepared in the current study by pre-amination with triethylene tetramine of a commercial poly(acrylonitrile) (PAN) fiber, followed by its subsequent grafting of glycidyl trimethylammonium chloride (GTA). The grafting conditions were optimized by orthogonal tests with GTA dosage, reaction temperature, reaction time and solvent composition etc. The produced QAPAN fibers were characterized by acid-base titration, analysis of tensile strength and optical microscope, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS). The adsorption properties of the prepared APAN and QAPAN fibers for Cr(VI) were studied.The optimal grafting reaction condition was GTA dosage 5 mL, reaction time 6 h, temperature 60℃and volume ratio of DI to DMSO 0.5:0.5. Total exchange capacity and strong base capacity for the QAPAN fibers prepared under the optimal amplified (×5) conditions were 6.34 mmol/g and 1.34 mmol/g, respectively. FTIR and XPS results showed that with this method, quaternary ammonium groups were successfully grafted onto PAN fibers. Microscope photographs and tensile strength results showed that, QAPAN fibers retained their excellent fibrous morphology and fine mechanical strength that made their further processing feasible.The adsorption capacity of the prepared APAN and QAPAN fibers were investigated by batch adsorption experiments and column adsorption experiments. Batch adsorption results showed that the QAPAN fiber had a less pronounced decrease of adsorption capacity under alkaline conditions in comparison with APAN fiber. The adsorption rate of APAN and QAPAN fibers were very fast and the equilibrium took only about 5 min. The adsorption isotherm of two fibers could be well fitted by Langmuir equation, with maximum adsorption capacity calculated to be 224 mg/g and 248 mg/g. SO42- had a substantial depressing effect on the adsorption capacity of two fibers. Column adsorption results showed that APAN and QAPAN fibers could be regenerated for repeated use in Cr(Ⅵ) wastewater processing. Results from this study proposed that the two ion exchange fibers have great potential application in the treatment of waste water.