_Article_  
Microwave Synthesis, Characterization and Perspectives of Wood Pencil-Derived Carbon  
[PERSON] 1,*, [PERSON] 1,*, [PERSON] 1, [PERSON] 1,*,  
Firing the dry sticks creates the graphite cores, which are then placed in wood casings to assemble the pencil.  
Besides writing and drawing, pencils have also attracted significant scientific attention. In the notorious case of a breakthrough discovery, they were originally served as the source of graphene in an unusual way to win a Nobel Prize in physics [1]. Moreover, due to the conductive nature of graphite, they are often used for creative science activities, such as electrodes for the electrolysis of water, to draw flexible graphite circuits on a paper or even to design on-skin electronics using pencil and paper. Worth mentioning towards this direction is also the popular web-based experiment of burning a pencil inside a domestic microwave oven. This experiment is one of the many performed in the course of putting various everyday objects into the microwave test by curiosity (e.g., aluminum foil, CDs, mirror, grapes, ivory soap, marshmallows, etc.). Graphite, being a good conductor of electricity, strongly interacts with microwaves to produce hot plasma [2; 3; 4; 5] that sets the pencil's wood casing alight. As a result, a wood-derived carbon residue is obtained after microwave ignition. It is staggering though that no report in the literature deals or even discusses on the structural characterization, morphological features and potential applications of this wood-derived carbon. By also considering that over 14 billion pencils are used globally every year as well as the fact that most of them are discarded until they become 60% shorter after use, one realizes that pencils do produce enough waste worth converting into useful material. This fact acquires even greater interest when set in the context of biomass-derived carbons using microwave heating [5], although viability and sustainability in the case of pencils might be considered weaker compared to a plentiful agriculture source. Moreover, the production cost and the negative environmental fingerprint of the graphite production process led many startup companies to search for a way to recycle pencils as well as how to organize networks for graphite recycling. The first stage for this valorization process will be the separation of the wood from the graphite core of the pencils. In this perspective, the method studied herein could be applied as the first stage and become economically viable.  
Based on these grounds, herein we present the microwave synthesis, characterization and potential application aspects of wood pencil-derived carbon, hence offering a fast and cost-effective way of converting pencil waste into applicable carbon material. First, we demonstrate that direct irradiation of wood pencil inside a domestic microwave oven for a couple of minutes generates hot graphite plasma, which ignites and carbonizes the pencil's wood casing. This results in carbon nanosheets, an important class of carbon nanomaterials with useful properties as catalyst supports or reinforcing fillers in polymer nanocomposites [6; 7]. Second, by exploiting the excellent adsorption capability of wood, we show that similar microwave treatment of the KOH-activated [8; 9] wood pencil results in porous carbon particles of a relatively high surface area. The obtained carbon decolorizes dye aqueous solutions, generates heat in pocket warmers when combined with metallic iron, sodium chloride and a small amount of water, forms the basis of gunpowder when properly mixed with KNO3 and S and efficiently removes the toxic hexavalent chromium Cr(VI) from water at an acidic pH (e.g., the pH of industrial wastewaters). The microwave synthesis, characterization and perspectives of wood pencil-derived carbon with and without activation are thereafter presented.