Novel Approach of Plastic Waste to Flash Graphene

Prof. Algozeeb and his research collaboration team have investigated an novel approach of upcycling plastic waste (PW) products to flash graphene (FG).

This method relies on Flash Joule Heating (FJH) to convert PW into FG. A sequential direct current (DC) and alternating current (AC) flash is used in order to make a high-quality graphene. In this FJH process, they established without catalyst and works for PW mixtures that can make the process suitable for handling landfill PW.

 In 21^st century, PW pollution is considerable one among the various environmental issues. A very large fraction of PW ends up in the ocean, which leads to the formation of micro- and nanoplastics that threaten marine life, micro-organisms, useful bacteria, and humans. From the intense carbon footprint process, most of these synthesized plastics are used only once before dumping into landfills or water ways that terminate in the oceans. Hence, upcycling PW to higher value materials and chemicals is economically and eco-friendly advantageous [1, 2].

 More effort has been directed toward physical recycling, in which the plastic is reshaped to reuse by the detergent washed for multiple times in order to reduce the amount of PW. But, physical recycling has major drawbacks, which include of grinding, milling, sterilizing and human-labor-intensive sorting of plastics. Another route for PW handling is chemical recycling of which the PW is pyrolyzed in an inert atmosphere or in the presence of a catalyst, that lead to the decomposing of the plastic into smaller molecules and oils. Hence, new technologies such as upcycling or greener recycling is sought, with the latter occurring, when the products reached to a higher value than the initial plastic [3].

Further, Prof. Algozeeb and his research team reported that their research work, mainly themes of an alternative approach to physical and chemical recycling by dealing with PW, and it is based upon their recently developed DC, DC-FJH method, which converts the carbon sources into graphene, with the process forming is called FG.

This technology relies on electricity to induce FJH in PW, which drives the carbon source in to high temperatures within a small interval of time. Hence, this process overcomes the need to pyrolyze the plastic in furnaces, where much of the energy is lost in the whole process. Meanwhile, the sequential AC and DC (ACDC) flash process was also shown to be attentive for upcycling both single stream thermoplastics and PW mixtures to make high-quality graphene [4].

Figure 1. Schematic Diagram of Flash Joule Heat Method. (Image Credit To: SNB Team). 

The degree of graphene dispersibility is considerable one of the important parameters that influences the processability of graphene into composites. Because of their hydrophilic tails and hydrophobic cores, pluronic surfactants are very cheap in price and often used to make stable aqueous graphene dispersions. Due to the turbostratic morphology that makes it easier, the ability of FG dispersions with high concentration is been achieved [4].

Further, they reported that, the high-quality FG is very difficult to achieve by direct DC-FJH treatment of PW without the AC-FJH. AC-FJH is essential for removing more volatiles from the PW to obtain high-quality. Also it can be seen that, the temperature rises to ∼2900 K, forcing the C−C bonds to break and rearrange to the more stable graphene during the AC-FJH processes [4].

Excess energy is released via light radiation, which results to in rapid cooling in the carbon material and a bright flash during every discharge. It can be noted that the most of elements like metals and silicon sublime below 2900 K, whereas carbon sublime at ∼3900 K. Hence, to obtain a high quality FG, this purification mechanism progress obviates the required to reject the contaminates like plasticizers, nanoclays, residual food, before using FJH. A characterization part (X-ray diffraction, XPS, and Raman Spectra) helpful to declare about the pure high-quality FG, interlayer distance, and morphology of ACDC-tFG.

Further, they observed that the nanoclays sublime (possibly after reduction) from the PW matrix during the FJH process to produce FG. Thus, FJH shows to be a effective to convert the PW mixtures to FG, this process makes a good choice for eliminating the intensive sorting steps (necessitated) using other recycling or reuse processes. It can also be seen that, if a similar amount of H₂ remains to be generated upon scaling, then the H₂ might be used in a fuel cell to generate clean supplemental electricity for the FJH process [4].

Our SNB team recommended this research article to enrich our viewer’s knowledge to know about the novel approach of upcycling PW products with a simple reliable method on FJH to convert into flash graphene. In general, it is a known fact that, graphene is found to be stable form of carbon with an extremely resilient structure. They reported that the initial analysis of gas-phase products shows the formation of considerable amounts of hydrogen along with other light hydrocarbons and carbon oligomers, in addition to FG. Therefore, the ability to using small amounts of electricity that converts PW to higher value materials moves the globe closer towards the plastic neutrality. Further, this FJH technology can be used in a large scale to handle PW which could potentially reduce the greenhouse gases emissions to upcycle for the use of plastics. Finally, they conclude that the graphene is found to be naturally occurring with a low toxicity profile, which could be an environmentally beneficial method to upcycle PW. Therefore, FJH of PW should be considered as a method to upcycle PW.

References

1. S. Barnes, Environ. Pollut.249, 812 (2019).
2. S.G. Tetu et al., Commun. Biol. 2, 184 (2019).
3. A. K. Panda, Catalyst. Int.J. Ind. Chem. 9, 167 (2018).
4. W.A. Algozeeb et al., ACS Nano, 2020, DOI: https://dx.doi.org/10.1021/acsnano.0c06328.

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Dr. Y. Sasikumar

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