The development of advanced engineering materials from low-cost renewable or waste resources is a key aspect of sustainability. Carbon nanofibers (CNFs) are a one-dimensional form of carbon with diameters in the submicron-and in the nanometer range with wide applicability in energy storage, catalysis, and adsorption. Lignin has recently emerged as a low-cost, biorenewable precursor for the production of CNFs. This comprehensive review presents the state-of-the-art of the manufacture of CNFs from lignin via the electrospinning technique. The first part of this review is concerned with the properties of lignin, the structure and applications of CNFs, especially for energy storage, and the description of the electrospinning method. The second part is focused on the different lignin-based precursor formulations for the manufacture of electrospun CNFs. These include the use of lignin alone or blended with other polymers at various mass ratios (polyacrylonitrile, poly(vinyl alcohol), poly(ethylene oxide), cellulose acetate, poly(ethylene terephthalate), and polyvinylpyrrolidone). In addition, different manufacturing approaches and strategies aiming to enhance the textural, mechanical, and electrochemical properties of CNFs are discussed in connection with their performance in relative applications.

The morphology of nanofibrous nonwoven mats of an electrospun biodegradable polymer nanocomposite was studied in order to define the material and process parameter settings capable of giving the targeted nanofibrous structure of the mats. The polymer solution concentration, the flow rate of the injected solution, and the organically modified clay content of the polymer matrix were the investigated factors according to a design of experiments (DoE) within the context of response-surface methodology (RSM). Three responses were defined and were estimated by image processing of the scanning electron microscopy (SEM) micrographs. The first two were the ratio of the average bead-to-fiber diameter D bead /D fiber and the number surface density of the beads N bead and were introduced to indicate the fibrous quality of the mats, while the third, indicative of the fiber thickness, was D fiber . The developed quadratic models and the individual and coupling effect of the three factors examined are given. The results suggest that the dominant parameter affecting mats' morphology is polymer solution concentration and that a broader range in the factor settings, especially for concentration, should be used in a subsequent optimization.

Utilizing inexpensive biorenewable and waste raw materials for the production of carbon nanofibers can pave the way for lowering their manufacturing cost. In this research, lignin is combined with recycled poly(ethylene terephthalate) (PET) to fabricate precursor fibers via electrospinning. The process is optimized using the Design of Experiments statistical methodology and fibers with minimum average diameter equal to 191 6 60 nm are prepared. Investigation with Attenuated Total Reflection -Fourier Transform Infrared Spectroscopy reveals the lignin structural changes induced by the solvent (trifluoroacetic acid), which is used for the preparation of homogeneous solutions of lignin and PET in various concentrations, while it gives an indication of the blending of the two electrospun polymers. The good miscibility between lignin and PET is also confirmed with Differential Scanning Calorimetry. The subsequent carbonization of the precursor fibrous mats results in a fibrous carbon structure with average fiber diameters similar to those of the precursor fibers. The successful transformation into carbon nanofibers is affirmed by Energy Dispersive X-ray Spectroscopy. The Carbon content of these nanofibers amounts to 94.3%. V C 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43936.

The increasing demand for cleaner fuels and the recent stringent regulations of commercial fuel specifications have driven the research of alternative methods to upgrade the current industrial desulfurization technology. Adsorptive desulfurization, the removal of refractory sulfur compounds using appropriate selective tailor-made adsorbents, has shown up as a promising alternative in the recent years. Carbon nanomaterials, namely, graphene, graphene oxide, carbon nanotubes and carbon nanofibers, show a significant potential as desulfurization adsorbents. Their surface area and porosity, their ability of easy functionalization, and their suitability to serve as a support of different types of adsorbents have rendered them attractive candidates for this purpose. In this review, after a presentation of the current industrial desulfurization practice and its limitations, the structure and properties of the carbon nanomaterials of interest will be described, followed by a detailed account of their applications in adsorptive desulfurization. The major literature findings and conclusions will be presented and discussed as a road map for future research in the field.