Preparation Of Modified Polyacrylonitrile Nanofiber Membrane And Its Absorption Properties

Amidoxime polyacrylonitrile (PAN) chelating nanofiber membranes were prepared bychemical modification, then the adsorption behaviour of the chelating fiber membrane onheavy metal ions were explored. Furthermore the PAN/β-cyclodextrin (β-CD) compositenanofiber membranes were also prepared, which the influence on the adsorption of theneutral red, a kind of organic dyes, was discussed. By analysising these experimental data,it could be deduced that these modified PAN nanofibers might be used as adsorbent in thisarea of industrial waste water treatment. The results are showed as following:Firstly, PAN nanofiber membranes were successfully prepared by electrospinning ofPAN solutions, then the PAN membranes were modified with amine oxime in the aqueousof hydroxylamine hydrochloride. By changing the reaction conditions, such as temperature,time, solution pH and concentration of hydroxylamine hydrochloride, the-CN conversionrate was evaluated respectively. By balancing the conversion rate, combined with FTIR,SEM characterization, the optimum reaction conditions were finally determined. Theseresults showed that as the increase of reaction temperature, time and the concentration ofthe hydroxylamine hydrochloride, the-CN conversion rate also increased obviously. ButPAN nanofibers membrane size shrinked a little with the increasing of temperature andhydroxylamine hydrochloride concentration, moreover the membranes’ color was gettingpale yellow.Thr adsorption of PAN chelating fiber membrane on Cu (Ⅱ), Fe (Ⅲ), Pb (Ⅱ)werestudied in detail. The adsorption effectiveness of different metal ions was analysed as wellas its dynamic behavior and the sorption isotherm adsorption. Results showed thatLangmuir adsorption isotherm curve could fits well adsorption data of chelating fiber, andthe coefficients were above0.990, showing that the metal ion chelating nanofibers surfaceachieved monolayer adsorption. Adsorption process of chelating fiber on metal ion can bedescribed by secondary dynamics equations, and kinetic studies have shown that oximeamine groups on metal ions adsorption processes were controlled by the diffusion of metalions and coordination reaction. Adsorption and desorption of chelating fiber membrane onCu (Ⅱ) experiments suggested that amine oxime PAN chelating fiber membrane can bereused. Thus Amidoxime PAN chelating nanofibers could have a potential application inthese areas of heavy metal pollution treatment, the enrichment and recovery of preciousmetals.PAN/β-CD composite nanofiber membranes were successfully prepared by electrospinning of PAN solution with addition of β-CD. PAN/β-CD nanofibers withdifferent mass fraction of β-CD (respective to PAN fraction0,10%,20%,40%,60%) werecharacterized by SEM, exhibiting smooth surface and uniform diameter. FTIR and XRDresults showed that β-CD, retaining its cavity structure evenly, distributed in PANnanofibers matrix. The adsorption behavior of neutral red was studied by UV-Vis spectra.The adsorption rate was calculated as high as78.0%when the mass fraction of β-CD was40%with respect to PAN. The adsorption process of neutral red into PAN/β-CD nanofibermembranes matched with the Langmuir isotherm model well.