Fabrication of Electrospun Dual-Responsive Polymer Blend Nanofibers and its Application on Heavy Metal Removal from Aqueous Phase

Abstract

Industrialization has indeed brought a revolutionary change and development on human lives, however it has also caused a lot of negative impacts on the environment; one of these is the contamination of the environment with heavy metals which, if not treated, can have a detrimental effect on the environment, biodiversity, and humans. Thus, there is a need for the removal of heavy metals, and adsorption is one of the widely used remediation techniques. In this study, multi-responsive PES-PDMAEMA nanofibers were fabricated via electrospinning and applied for the adsorption of Cu2+ from synthetic wastewater. The nanofibers were fabricated using a mixture of DMF/NMP solvents, and the effects of polymer concentration and PES/PDMAEMA blend ratio on the morphology of the nanofiber were determined. It was found that uniform and bead-free nanofibers were obtained at 35 w/v% polymer concentration at PES/PDMAEMA blend ratio greater than 50:50. Moreover, FTIR spectra and EDX elemental mapping showed that PES and PDMAEMA were successfully blended into the nanofibers. Adsorption of Cu2+ was done using different PES/PDMAEMA blend ratios and the combined effects of pH and temperature were studied. Nanofibers made of 70:30 PES/PDMAEMA was used in subsequent adsorption experiments and results show that the maximum adsorption capacity was observed at pH 6.5 and 55 ℃. Fitting the adsorption data to the pseudo-second order kinetic model, it was found that increasing the temperature, resulted to increase in the equilibrium adsorption capacity and rate of Cu2+ uptake by the PES/PDMAEMA nanofibers. This indicates that the Cu2+ removal by adsorption on the nanofibers is favored by a high temperature condition, which can be the result of an increased mobility of the metal ions with temperature and the polymer’s response to temperature. Using Langmuir and Freundlich isotherms, the values of RL and 1/n indicate that the adsorption of Cu2+ onto the nanofibers is favorable. The maximum adsorption capacity, qm, were calculated to be 50, 88.5, and 161.30 mg.g-1 for 25, 35, and 55 ℃, respectively. The effects of pH and temperature on the desorption of Cu2+ from the PES/PDMAEMA nanofibers was also studied. Results show that the maximum desorption value of 85% was observed at pH 3 and 25 ℃. Finally, reusability study was done for 5 adsorption cycles. In conclusion, PES/PDMAEMA has the capability to adsorb and desorb Cu2+ just by adjusting the pH and temperature, hence it can be considered as an efficient and economical adsorbent for heavy metals such Cu2+.