Mesoporous PAA/dextran-polyaniline core-shell nanofibers: Optimization of producing conditions, characterization and heavy metal adsorptions

In this paper, mesoporous PAA/dextran-polyaniline core-shell nanofibers were prepared with combination of electrospinning and in-situ polymerization methods and their heavy metal adsorption ability was investigated. The result showed that PAA and dextran can be fully crosslinked through the esterification reaction via a heat-treatment method. Polyaniline with flake like structure was deposited on the nanofiber surface resulted in high surface area and mesoporous structure of nanofibers. The amount of pores was increased by removing the calcium carbonate nanoparticles incorporated on the nanofiber surface during the polymerization process. The synthesized nanofibers showed high maximum adsorption capacity of 1111.11 and 833.33 mg/g for Pb and Cu, respectively obtained from Langmuir isotherm model. It was found that the intra-particle diffusion controls the adsorption process and the plot presented three-step linearity. However, the adsorption followed the pseudo-second order kinetic model. An investigation on the activation energy value revealed that physical adsorption occurred in removing the heavy metals from solution resulted in high regeneration and reuse ability of the nanofibers even after 10 adsorption/desorption cycles. Since, the removing of metal ions by nanofibers occurred by electrostatic attractions, the solution pH played an important role in adsorption process. In this study, the optimum pH value was 7.5. Any decrease and increase in pH values caused to decrease the removal efficiency. (C) 2018 Published by Elsevier B.V. on behalf of Taiwan Institute of Chemical Engineers.