Synthesis of amidoximated polyacrylonitrile fibers and its use as adsorbent for Cr (VI) ions removal from aqueous solutions

Functionalized fibers, especially polyacrylonitrile fibers (PANF), have attracted wide interest as an effective and economical material for environment and water protection. In this study, polyacrylonitrile fibers modified with hydroxylamine hydrochloride were used as an adsorbent to remove hexavalent chromium ions from aqueous solutions. The novelty of the present study compared to the literature is the functionalization of polyacrylonitrile fibers surface by optimizing cost and energy while achieving a yield fast removal rate and high adsorption capacity of hexavalent chromium from aqueous solutions. The amidoximated polyacrylonitrile fibers were characterized using Fourier Transform InfraRed spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). The results confirmed the success of polyacrylonitrile fibers modification. The adsorption capacity was evaluated by investigating the effect of initial pH solution ranging from 2.0 to 7.0, the adsorbent dose varied from 0.05 to 0.25 g, the initial Cr (VI) concentration range was (5–70 mg g−1), the temperature varied from 5 to 60°C, and the contact time ranged from 0 to 180 min. We have used the Langmuir and Freundlich adsorption models to describe the equilibrium sorption data. The maximum adsorption capacity estimated using the Langmuir model reached 32. 57 mg g−1 under optimal conditions. The thermodynamic parameters (ΔG, ΔH, and ΔS) were also determined. In addition, the adsorbent showed a desorption rate of Cr (VI) up to 92% with 0.5 mol of NaOH, which can be reused for three adsorption–desorption cycles. The overall data showed the efficiency of amidoximated polyacrylonitrile fibers in removing Cr (VI) from aqueous solutions. © 2019 American Institute of Chemical Engineers Environ Prog, 38:e13146, 2019