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.
Highlights
The global increase in unconventional crude oil resources in recent years has resulted in increasing quantities of sour crudes, acidic crudes, or extra heavy crudes being produced (Zhang, 2002)
The increase in the solution electrical conductivity with increasing solution concentration could be due to hopping of charged species between conducting polymer chains resulting from the dissolution of polyethylene terephthalate (PET)/linear polyethylenimine (L-PEI) in the acidic condition of the solutions (Schmidt et al, 2012)
The present study has demonstrated the feasibility of preparing novel nickel vanadyl molecularly imprinted nanofiber (NVMIN) using nickel tetraphenylporphyrin (NTPP) and vanadyl tetraphenylporphyrin (VTPP) as the mixed-templates for the recognition and selective removal of a group of metalloporphyrins from organic media
Summary
The global increase in unconventional crude oil resources in recent years has resulted in increasing quantities of sour crudes, acidic crudes, or extra heavy crudes being produced (Zhang, 2002). Variety of metal compounds with vanadium and nickel being the major metals. Cantarell crude oil contains more than 243 μg/g vanadium and nickel, Tahe crude oil has more than 400 μg/g, and Bolivar Coastal crude oil from Lake Maracaibo, Venezuela has excess of 1200 μg/g of these metals (Xuet al., 2001)
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