Fabrication of chitosan composite nanofibers for the recovery of precious palladium cations from aqueous solution

In this paper, chitosan composite nanofibers with mean diameters of 300–500 nm have been prepared by electrospinning with poly(methacrylic acid) as the crosslinking agent and poly(ethylene oxide) as the cospinning polymer. Afterwards, these composite nanofibers were annealed at temperatures ranging from 110 to 190 °C to improve their solvent resistance. Their morphologies and structures were characterized by scanning electron microscopy, infrared spectroscopy (IR) and positron annihilation life spectroscopy. These composite nanofibers were used to adsorb the Pd2+ cations in aqueous solutions. The effects of chitosan content, annealing temperature, adsorption temperature, solution pH and initial Pd2+ concentration were carefully studied. The adsorption result shows that these composite nanofibers had better adsorption performance than the pristine chitosan and commercial activated carbon. Under the optimized adsorption conditions, the maximum adsorption capacity was found to be 366 mg/g. The adsorption kinetic, FT-IR and XPS confirmed the chemical adsorption behavior of Pd2+ cations on the composite nanofibers. The thermodynamic parameters (ΔG0, ΔH0 and ΔS0) acquired by Van’t Hoff equation indicated that the adsorption process was spontaneous and exothermic in nature. Moreover, selective adsorption study revealed that these composite nanofibers exhibited good adsorption selectivity for Pd2+ cations from the mixture of metal ions in aqueous solution. At last, the reusability of these novel composite nanofibers was tested for four runs. Overall, this study indicated that the as-prepared nanofiber mat was an efficient adsorbent for the recovery of precious palladium cations from aqueous solutions.