Fabrication and evaluation of multiple template cross-linked molecularly imprinted electro spun nanofibers for selective extraction of nickel and vanadyl tetraphenylporphyrin from organic media

Abstract

A nickel vanadyl molecularly imprinted nanofiber (NVMIN) was developed by the electrospinning technique, employing polyethylene terephthalate (PET) and linear polyethylenimine (L-PEI) as the matrix polymers, nickel tetraphenylporphyrin (NTPP) and vanadyl tetraphenylporphyrin (VTPP) as the mixed-template molecules. The fabricated NVMIN was evaluated as a sorbent for the removal of NTPP and VTPP from organic media. The effects of trifluoroacetic acid (TFA), dichloromethane (DCM), dimethyl sulphoxide (DMSO), pentane (PEN) on electro-spinnability of the PET/L-PEI solutions and the morphological appearance of the PET/L-PEI fibers were investigated qualitatively by means of a scanning electron microscope (SEM). Electrospinning of 14 to 30% w/v PET/L-PEI solutions in TFA produced beaded and smooth fibers, depending on the concentration range. The addition of DCM and PEN as modifiers helped improve the electrospinnability, with PEN being the best, while the addition of DMSO made the solutions not spinnable. The results indicated that the NVMIN showed higher affinity (99% higher) for NTPP than the non-imprinted nanofiber (NIN) indicating that the NVMIN contained a lot of specific binding sites. It was determined that the NVMIN exhibited the same selectivity specialism for both NTPP and VTPP. However, the interaction strength was strongly dependant on the type of solvent, where the strongest interaction was achieved in chloroform. In addition, the thermodynamic parameters calculated from the adsorption data suggested that the adsorption of NTPP onto NVMIN was a spontaneous and exothermic process. Key words: Electrospinning, mixed-templates, adsorption, demetallation, solvents.