Preparation of Polyacrylonitrile Composite Nanofiber Membrane and Its Adsorption Property for Metal Ions

Using carboxyl modified polyacrylonitrile (CPAN) and β-cyclodextrin (β-CD) as spinning raw materials, β-CD/CPAN composite nanofiber membrane was prepared by electrostatic spinning process, and β-CD/CPAN-g-PEI composite nanofiber membrane was prepared by active modification of carboxyl groups on the fiber membrane with the grafting of polyethyleneimine(PEI). Through both compound modification and grafting modification, β-CD and PEI were introduced to the fiber membrane with the aim to enhance adsorption and mechanical property of the fiber membrane. The structure and performance of composite nanofiber membranes were characterized by infrared spectroscopy, X-ray diffraction, universal material testing machine, field emission scanning electron microscopy. The adsorption property and adsorption mechanism for Cd²⁺ and Pb²⁺ were investigated by using plasma emission spectrometer and X-ray photoelectron spectrometer. The results showed that β-CD was mixed in the fiber membrane, and PEI was successfully grafted onto the fiber membrane without causing the destruction of cyano radical and loss of β-CD. β-CD/CPAN-g-PEI composite nanofiber membrane exhibited excellent adsorption property for Cd²⁺and Pb²⁺, while retaining the original mechanical property. According to static adsorption experiments, the maximum adsorption capacities of β-CD/CPAN-g-PEI composite nanofiber membrane for Cd²⁺ and Pb²⁺ were 176.67 mg/g and 240.83 mg/g, respectively. The adsorption process of β-CD/CPAN-g-PEI composite nanofiber membrane conformed to the pseudo-second-order kinetic model and Langmuir isothermal adsorption model, indicating that β-CD/CPAN-g-PEI composite nanofiber membrane mainly exhibited single-layer chemical adsorption for Cd²⁺and Pb²⁺. Moreover, β-CD/CPAN-g-PEI composite nanofiber membrane had good reusability, and maintained more than 80% adsorption property for Cd²⁺ and Pb²⁺ after 5 cycles of use.