Modification of pre-oxidized polyacrylonitrile fibers as chelating sorbents for removal of Copper(II) ions

Abstract

Pre-oxidized polyacrylonitrile (PAN) fibers were chemically modified by sulfuric acid. In the process, conjugated imine sequences were retained and amide groups were transformed from unreacted nitrile groups. The adsorption experiments of Cu(II) ions by modified PAN fibers indicated that the adsorption capacities were significantly improved by increasing initial concentrations of metal ions, reaction time and temperature. The adsorption equilibriums followed Langmuir isotherm with correlation coefficients greater than 0.99. Kinetics analysis demonstrated that the adsorption of copper ions on the modified fiber was fitted well with pseudo-second-order kinetics equation. Indicated by energy dispersive X-ray (EDX) and X-ray photoelectron spectroscopy (XPS) results, channels for metal ions diffusing from the surface to the inner of the fiber were generated by the strong etching of sulfuric acid. The active sites of conjugated imine sequences and amides in the whole modified fiber can thus be easily accessed by the metal ions.