Heavy metal ions contamination in wastewater has drawn much attention due to a great threat to human health. Metal ions such as copper, iron, lead, and chromium, have high toxic and nonbiodegradable properties. Generally, adsorption is regarded as an effective and economical method for the removal and recovery of heavy metal ions. The adsorption properties of adsorbents depend on the functional groups on their surfaces. Recently, the electrospinning technique has become a versatile approach for producing nanofibers with high surface area-to-volume and flexibility for chemical/physical functionalization. It has been found that an adsorbent containing nitrogen-based ligands is effective in forming complexation with metal ions. As a kind of commodity textile materials, polyacrylonitrile (PAN) electrospinning nanofibers could be modified to contain a chelating group for the removal of metal ions. It is therefore of our interest to investigate the feasibility of using a nanofiber membranes modified with amine groups on its surface as an adsorbent of metal ions.
Firstly, PAN nanofiber membranes were successfully prepared by electrospinning of PAN/DMF solutions, then the PAN membranes were modified with amine oxime in the aqueous of hydroxylamine hydrochloride. These results showed that as the increase of reaction temperature, reaction time and the concentration of the hydroxylamine hydrochloride, the -CN conversion ratio also increased obviously. However PAN chelating nanofiber membranes size shrinked a little with the increasing of temperature and hydroxylamine hydrochloride concentration, moreover the membranes’ color was getting pale yellow. By combining with FTIR, SEM characterization, the optimum reaction conditions parameters were finally determined.
The adsorption effectiveness of Cu(II), Pb (II), Fe (III) , after 10h equilibria were 35.8, 75.2, and 90.0mg/g, respectively. Results showed that Langmuir adsorption isotherm curve could fits well adsorption data of chelating fiber, and the coefficients were above 0.990, showing that the metal ion chelating nanofibers surface achieved monolayer adsorption. Adsorption process of chelating fiber on metal ion can be described by secondary dynamics equations, and kinetic studies have shown that oxime amine groups on metal ions adsorption processes were controlled by the diffusion of metal ions and coordination reaction. Adsorption and desorption of chelating fiber membranes on Cu (II) experiments suggested that amine oxime PAN chelating fiber membrane can be facilely regenerated with hydrochloric acid solution. Thus Amidoxime PAN chelating nanofibers could have a potential application in these areas of heavy metal ions pollution treatment, the enrichment and recovery of precious metals.